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  • 1.
    Ali, Azmat
    et al.
    Sorbonne Université, CNRS, Institut des Nanosciences de Paris, INSP, F-75005, Paris, France.
    Cruguel, Herve
    Sorbonne Université, CNRS, Institut des Nanosciences de Paris, INSP, F-75005, Paris, France.
    Giangrisostomi, Erika
    Institute Methods and Instrumentation for Synchrotron Radiation Research PS-ISRR, Helmholtz Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489, Berlin, Germany.
    Ovsyannikov, Ruslan
    Institute Methods and Instrumentation for Synchrotron Radiation Research PS-ISRR, Helmholtz Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489, Berlin, Germany.
    Silly, Mathieu G.
    Synchrotron SOLEIL, l‘Orme des Merisiers, Saint-Aubin, Boîte Postale 48, 9119, Gif-sur-Yvette Cedex, France.
    Dudy, Lenart
    Synchrotron SOLEIL, l‘Orme des Merisiers, Saint-Aubin, Boîte Postale 48, 9119, Gif-sur-Yvette Cedex, France.
    Cappel, Ute B.
    Division of Applied Physical Chemistry, Department of Chemistry, KTH − Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
    Lhuillier, Emmanuel
    Sorbonne Université, CNRS, Institut des Nanosciences de Paris, INSP, F-75005, Paris, France.
    Witkowski, Nadine
    Sorbonne Université, CNRS, Institut des Nanosciences de Paris, INSP, F-75005, Paris, France.
    Johansson, Fredrik
    Sorbonne Université, CNRS, Institut des Nanosciences de Paris, INSP, F-75005, Paris, France;Division of Applied Physical Chemistry, Department of Chemistry, KTH − Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
    The Electronic Impact of Light-Induced Degradation in CsPbBr3 Perovskite Nanocrystals at Gold Interfaces2024In: The Journal of Physical Chemistry Letters, E-ISSN 1948-7185, Vol. 15, no 14, p. 3721-3727Article in journal (Refereed)
    Abstract [en]

    The understanding of the interfacial properties in perovskite devices under irradiation is crucial for their engineering. In this study we show how the electronic structure of the interface between CsPbBr3 perovskite nanocrystals (PNCs) and Au is affected by irradiation of X-rays, near-infrared (NIR), and ultraviolet (UV) light. The effects of X-ray and light exposure could be differentiated by employing low-dose X-ray photoelectron spectroscopy (XPS). Apart from the common degradation product of metallic lead (Pb0), a new intermediate component (Pbint) was identified in the Pb 4f XPS spectra after exposure to high intensity X-rays or UV light. The Pbint component is determined to be monolayer metallic Pb on-top of the Au substrate from underpotential deposition (UPD) of Pb induced from the breaking of the perovskite structure allowing for migration of Pb2+.

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  • 2. Andaji-Garmaroudi, Z.
    et al.
    Abdi-Jalebi, M.
    Kosasih, F. U.
    Doherty, T.
    Macpherson, S.
    Bowman, A. R.
    Man, G. J.
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Rensmo, H.
    Ducati, C.
    Friend, R. H.
    Stranks, S. D.
    Elucidating and Mitigating Degradation Processes in Perovskite Light-Emitting Diodes2020In: Advanced Energy Materials, ISSN 1614-6832, E-ISSN 1614-6840, Vol. 10, no 48, article id 2002676Article in journal (Refereed)
    Abstract [en]

    Halide perovskites have attracted substantial interest for their potential as disruptive display and lighting technologies. However, perovskite light-emitting diodes (PeLEDs) are still hindered by poor operational stability. A fundamental understanding of the degradation processes is lacking but will be key to mitigating these pathways. Here, a combination of in operando and ex situ measurements to monitor the performance degradation of (Cs0.06FA0.79MA0.15)Pb(I0.85Br0.15)3 PeLEDs over time is used. Through device, nanoscale cross-sectional chemical mapping, and optical spectroscopy measurements, it is revealed that the degraded performance arises from an irreversible accumulation of bromide content at one interface, which leads to barriers to injection of charge carriers and thus increased nonradiative recombination. This ionic segregation is impeded by passivating the perovskite films with potassium halides, which immobilizes the excess halide species. The passivated PeLEDs show enhanced external quantum efficiency (EQE) from 0.5% to 4.5% and, importantly, show significantly enhanced stability, with minimal performance roll-off even at high current densities (>200 mA cm−2). The decay half-life for the devices under continuous operation at peak EQE increases from <1 to ≈15 h through passivation, and ≈200 h under pulsed operation. The results provide generalized insight into degradation pathways in PeLEDs and highlight routes to overcome these challenges.

  • 3.
    Andaji-Garmaroudi, Zahra
    et al.
    Univ Cambridge, Cavendish Lab, Dept Phys, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Abdi-Jalebi, Mojtaba
    Univ Cambridge, Cavendish Lab, Dept Phys, JJ Thomson Ave, Cambridge CB3 0HE, England.;UCL, Inst Mat Discovery, Torrington Pl, London WC1E 7JE, England..
    Kosasih, Felix U.
    Univ Cambridge, Dept Mat Sci & Met, 27 Charles Babbage Rd, Cambridge CB3 0FS, England..
    Doherty, Tiarnan
    Univ Cambridge, Cavendish Lab, Dept Phys, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Macpherson, Stuart
    Univ Cambridge, Cavendish Lab, Dept Phys, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Bowman, Alan R.
    Univ Cambridge, Cavendish Lab, Dept Phys, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Man, Gabriel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Cappel, Ute B.
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Ducati, Caterina
    Univ Cambridge, Dept Mat Sci & Met, 27 Charles Babbage Rd, Cambridge CB3 0FS, England..
    Friend, Richard H.
    Univ Cambridge, Cavendish Lab, Dept Phys, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Stranks, Samuel D.
    Univ Cambridge, Cavendish Lab, Dept Phys, JJ Thomson Ave, Cambridge CB3 0HE, England.;Univ Cambridge, Dept Chem Engn & Biotechnol, Philippa Fawcett Dr, Cambridge CB3 0AS, England..
    Elucidating and Mitigating Degradation Processes in Perovskite Light-Emitting Diodes2020In: Advanced Energy Materials, ISSN 1614-6832, E-ISSN 1614-6840, Vol. 10, no 48, article id 2002676Article in journal (Refereed)
    Abstract [en]

    Halide perovskites have attracted substantial interest for their potential as disruptive display and lighting technologies. However, perovskite light-emitting diodes (PeLEDs) are still hindered by poor operational stability. A fundamental understanding of the degradation processes is lacking but will be key to mitigating these pathways. Here, a combination of in operando and ex situ measurements to monitor the performance degradation of (Cs(0.06)FA(0.79)MA(0.15))Pb(I0.85Br0.15)(3) PeLEDs over time is used. Through device, nanoscale cross-sectional chemical mapping, and optical spectroscopy measurements, it is revealed that the degraded performance arises from an irreversible accumulation of bromide content at one interface, which leads to barriers to injection of charge carriers and thus increased nonradiative recombination. This ionic segregation is impeded by passivating the perovskite films with potassium halides, which immobilizes the excess halide species. The passivated PeLEDs show enhanced external quantum efficiency (EQE) from 0.5% to 4.5% and, importantly, show significantly enhanced stability, with minimal performance roll-off even at high current densities (>200 mA cm(-2)). The decay half-life for the devices under continuous operation at peak EQE increases from <1 to approximate to 15 h through passivation, and approximate to 200 h under pulsed operation. The results provide generalized insight into degradation pathways in PeLEDs and highlight routes to overcome these challenges.

  • 4. Aung, S. H.
    et al.
    Zhao, L.
    Nonomura, K.
    Oo, T. Z.
    Zakeeruddin, S. M.
    Vlachopoulos, N.
    Sloboda, Tamara
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Svanström, S.
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Hagfeldt, A.
    Grätzel, M.
    Toward an alternative approach for the preparation of low-temperature titanium dioxide blocking underlayers for perovskite solar cells2019In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, no 17, p. 10729-10738Article in journal (Refereed)
    Abstract [en]

    The anodic electrodeposition method is investigated as an alternative technique for the preparation of a titanium oxide (TiO 2 ) blocking underlayer (UL) for perovskite solar cells (PSCs). Extremely thin Ti IV -based films are grown from aqueous acidic titanium(iii) chloride in an electrochemical cell at room temperature. This precursor layer is converted to the UL (ED-UL), in a suitable state for PSC applications, by undertaking a sintering step at 450 °C for half an hour. PSCs with the composition of the light-absorbing material FA 0.85 MA 0.10 Cs 0.05 Pb(I 0.87 Br 0.13 ) 3 (FA and MA denote the formamidinium and methylammonium cations, respectively) based on the ED-UL are compared with PSCs with the UL of a standard type prepared by the spray-pyrolysis method at 450 °C from titanium diisopropoxide bis(acetylacetonate) (SP-UL). We obtain power conversion efficiencies (PCEs) of over 20% for mesoscopic perovskite devices employing both ED-ULs and SP-ULs. Slightly higher fill factor values are observed for ED-UL-based devices. In addition, ED-ULs prepared by the same method have also been applied in planar PSCs, resulting in a PCE exceeding 17%, which is comparable to that for similar PSCs with an SP-UL. The preparation of ED-ULs with a lower sintering temperature, 150 °C, has also been examined. The efficiency of a planar PSC incorporating this underlayer was 14%. These results point out to the possibility of applying ED-ULs in flexible planar PSCs in the future.

  • 5.
    Aung, Su Htike
    et al.
    Swiss Fed Inst Technol Lausanne EPFL, EPFL SB ISIC LSPM, Inst Chem Sci & Engn, Lab Photomol Sci, Chemin Alambics,Stn 6, CH-1015 Lausanne, Switzerland;Shwebo Univ, Phys Dept, Shwebo 02261, Myanmar;Univ Mandalay, Dept Phys, Mat Res Lab, Mandalay 05032, Myanmar.
    Zhao, Lichen
    Swiss Fed Inst Technol Lausanne EPFL, EPFL SB ISIC LPI, Lab Photon & Interfaces, Inst Chem Sci & Engn, Chemin Alambics,Stn 6, CH-1015 Lausanne, Switzerland;Peking Univ, Dept Phys, State Key Lab Artificial Microstruct & Mesoscop P, Beijing 100871, Peoples R China.
    Nonomura, Kazuteru
    Swiss Fed Inst Technol Lausanne EPFL, EPFL SB ISIC LSPM, Inst Chem Sci & Engn, Lab Photomol Sci, Chemin Alambics,Stn 6, CH-1015 Lausanne, Switzerland.
    Oo, Than Zaw
    Univ Mandalay, Dept Phys, Mat Res Lab, Mandalay 05032, Myanmar.
    Zakeeruddin, Shaik M.
    Swiss Fed Inst Technol Lausanne EPFL, EPFL SB ISIC LPI, Lab Photon & Interfaces, Inst Chem Sci & Engn, Chemin Alambics,Stn 6, CH-1015 Lausanne, Switzerland.
    Vlachopoulos, Nick
    Swiss Fed Inst Technol Lausanne EPFL, EPFL SB ISIC LSPM, Inst Chem Sci & Engn, Lab Photomol Sci, Chemin Alambics,Stn 6, CH-1015 Lausanne, Switzerland.
    Sloboda, Tamara
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden.
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute B.
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden.
    Hagfeldt, Anders
    Swiss Fed Inst Technol Lausanne EPFL, EPFL SB ISIC LSPM, Inst Chem Sci & Engn, Lab Photomol Sci, Chemin Alambics,Stn 6, CH-1015 Lausanne, Switzerland.
    Graetzel, Michael
    Swiss Fed Inst Technol Lausanne EPFL, EPFL SB ISIC LPI, Lab Photon & Interfaces, Inst Chem Sci & Engn, Chemin Alambics,Stn 6, CH-1015 Lausanne, Switzerland.
    Toward an alternative approach for the preparation of low-temperature titanium dioxide blocking underlayers for perovskite solar cells2019In: Journal of Materials Chemistry A, ISSN 2050-7488, E-ISSN 2050-7496, Vol. 7, no 17, p. 10729-10738Article in journal (Refereed)
    Abstract [en]

    The anodic electrodeposition method is investigated as an alternative technique for the preparation of a titanium oxide (TiO2) blocking underlayer (UL) for perovskite solar cells (PSCs). Extremely thin Ti-IV-based films are grown from aqueous acidic titanium(III) chloride in an electrochemical cell at room temperature. This precursor layer is converted to the UL (ED-UL), in a suitable state for PSC applications, by undertaking a sintering step at 450 degrees C for half an hour. PSCs with the composition of the light-absorbing material FA(0.85)MA(0.10)Cs(0.05)Pb(I0.87Br0.13)(3) (FA and MA denote the formamidinium and methylammonium cations, respectively) based on the ED-UL are compared with PSCs with the UL of a standard type prepared by the spray-pyrolysis method at 450 degrees C from titanium diisopropoxide bis(acetylacetonate) (SP-UL). We obtain power conversion efficiencies (PCEs) of over 20% for mesoscopic perovskite devices employing both ED-ULs and SP-ULs. Slightly higher fill factor values are observed for ED-UL-based devices. In addition, ED-ULs prepared by the same method have also been applied in planar PSCs, resulting in a PCE exceeding 17%, which is comparable to that for similar PSCs with an SP-UL. The preparation of ED-ULs with a lower sintering temperature, 150 degrees C, has also been examined. The efficiency of a planar PSC incorporating this underlayer was 14%. These results point out to the possibility of applying ED-ULs in flexible planar PSCs in the future.

  • 6.
    Berggren, Elin
    et al.
    Uppsala Univ, Dept Phys & Astron, Div X Ray Photon Sci, SE-75120 Uppsala, Sweden..
    Weng, Yi-Chen
    Uppsala Univ, Dept Phys & Astron, Div X Ray Photon Sci, SE-75120 Uppsala, Sweden..
    Li, Qifan
    Linköping Univ, Dept Sci & Technol, Lab Organ Elect, SE-60174 Norrköping, Sweden..
    Yang, Chi-Yuan
    Linköping Univ, Dept Sci & Technol, Lab Organ Elect, SE-60174 Norrköping, Sweden..
    Johansson, Fredrik
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. Sorbonne Univ, Inst Nanosci Paris, CNRS, INSP, F-75005 Paris, France..
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Berggren, Magnus
    Linköping Univ, Dept Sci & Technol, Lab Organ Elect, SE-60174 Norrköping, Sweden..
    Fabiano, Simone
    Linköping Univ, Dept Sci & Technol, Lab Organ Elect, SE-60174 Norrköping, Sweden..
    Lindblad, Andreas
    Uppsala Univ, Dept Phys & Astron, Div X Ray Photon Sci, SE-75120 Uppsala, Sweden..
    Charge Transfer in the P(g42T-T): BBL Organic Polymer Heterojunction Measured with Core-Hole Clock Spectroscopy2023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 49, p. 23733-23742Article in journal (Refereed)
    Abstract [en]

    The conductivity of organic polymer heterojunction devices relies on the electron dynamics occurring along interfaces between the acceptor and donor moieties. To investigate these dynamics with chemical specificity, spectroscopic techniques are employed to obtain localized snapshots of the electron behavior at selected interfaces. In this study, charge transfer in blends (by weight 10, 50, 90, and 100%) of p-type polymer P(g(4)2T-T) (bithiophene-thiophene) and n-type polymer BBL (poly(benzimidazo-benzo-phenanthroline)) was measured by resonant Auger spectroscopy. Electron spectra emanating from the decay of core-excited states created upon X-ray absorption in the donor polymer P(g(4)2T-T) were measured in the sulfur KL2,3L2,3 Auger kinetic energy region as a function of the excitation energy. By tuning the photon energy across the sulfur K-absorption edge, it is possible to differentiate between decay paths in which the core-excited electron remained on the atom with the core-hole and those where it tunneled away. Analyzing the competing decay modes of these localized and delocalized (charge-transfer) processes facilitated the computation of charge-transfer times as a function of excitation energy using the core-hole clock method. The electron delocalization times derived from the measurements were found to be in the as/fs regime for all polymer blends, with the fastest charge transfer occurring in the sample with an equal amount of donor and acceptor polymer. These findings highlight the significance of core-hole clock spectroscopy as a chemically specific tool for examining the local charge tunneling propensity, which is fundamental to understanding macroscopic conductivity. Additionally, the X-ray absorption spectra near the sulfur K-edge in the P(g(4)2T-T) polymer for different polymer blends were analyzed to compare molecular structure, orientation, and ordering in the polymer heterojunctions. The 50% donor sample exhibited the most pronounced angular dependence of absorption, indicating a higher level of ordering compared to the other weight blends. Our studies on the electron dynamics of this type of all-polymer donor-acceptor systems, in which spontaneous ground-state electron transfer occurs, provide us with critical insights to further advance the next generation of organic conductors with mixed electron-hole conduction characteristics suitable for highly stable electrodes of relevance for electronic, electrochemical, and optoelectronic applications.

  • 7.
    Berggren, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Weng, Yi-Chen
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Li, Qifan
    Linköping Univ, Dept Sci & Technol, Lab Organ Elect, SE-60174 Norrköping, Sweden..
    Yang, Chi-Yuan
    Linköping Univ, Dept Sci & Technol, Lab Organ Elect, SE-60174 Norrköping, Sweden..
    Johansson, Fredrik
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden.;Sorbonne Univ, Inst Nanosci Paris, CNRS, INSP, F-75005 Paris, France..
    Cappel, Ute B.
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Berggren, Magnus
    Linköping Univ, Dept Sci & Technol, Lab Organ Elect, SE-60174 Norrköping, Sweden..
    Fabiano, Simone
    Linköping Univ, Dept Sci & Technol, Lab Organ Elect, SE-60174 Norrköping, Sweden..
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Charge Transfer in the P(g42T-T):BBL Organic Polymer Heterojunction Measured with Core-Hole Clock Spectroscopy2023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 49, p. 23733-23742Article in journal (Refereed)
    Abstract [en]

    The conductivity of organic polymer heterojunction devices relies on the electron dynamics occurring along interfaces between the acceptor and donor moieties. To investigate these dynamics with chemical specificity, spectroscopic techniques are employed to obtain localized snapshots of the electron behavior at selected interfaces. In this study, charge transfer in blends (by weight 10, 50, 90, and 100%) of p-type polymer P(g(4)2T-T) (bithiophene-thiophene) and n-type polymer BBL (poly(benzimidazo-benzo-phenanthroline)) was measured by resonant Auger spectroscopy. Electron spectra emanating from the decay of core-excited states created upon X-ray absorption in the donor polymer P(g(4)2T-T) were measured in the sulfur KL2,3L2,3 Auger kinetic energy region as a function of the excitation energy. By tuning the photon energy across the sulfur K-absorption edge, it is possible to differentiate between decay paths in which the core-excited electron remained on the atom with the core-hole and those where it tunneled away. Analyzing the competing decay modes of these localized and delocalized (charge-transfer) processes facilitated the computation of charge-transfer times as a function of excitation energy using the core-hole clock method. The electron delocalization times derived from the measurements were found to be in the as/fs regime for all polymer blends, with the fastest charge transfer occurring in the sample with an equal amount of donor and acceptor polymer. These findings highlight the significance of core-hole clock spectroscopy as a chemically specific tool for examining the local charge tunneling propensity, which is fundamental to understanding macroscopic conductivity. Additionally, the X-ray absorption spectra near the sulfur K-edge in the P(g(4)2T-T) polymer for different polymer blends were analyzed to compare molecular structure, orientation, and ordering in the polymer heterojunctions. The 50% donor sample exhibited the most pronounced angular dependence of absorption, indicating a higher level of ordering compared to the other weight blends. Our studies on the electron dynamics of this type of all-polymer donor-acceptor systems, in which spontaneous ground-state electron transfer occurs, provide us with critical insights to further advance the next generation of organic conductors with mixed electron-hole conduction characteristics suitable for highly stable electrodes of relevance for electronic, electrochemical, and optoelectronic applications.

    Download full text (pdf)
    fulltext
  • 8. Cappel, U. B.
    et al.
    Gibson, E. A.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Uppsala University, Sweden.
    Boschloo, G.
    Dye regeneration by Spiro-MeOTAD in solid state dye-sensitized solar cells studied by photoinduced absorption spectroscopy and spectroelectrochemistry2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 15, p. 6275-6281Article in journal (Refereed)
    Abstract [en]

    Photoinduced absorption (PIA) spectroscopy is presented as a tool for the systematic study of dye regeneration and pore filling in solid state dye-sensitized solar cells (DSC). Oxidation potentials and extinction coefficients for oxidized species of the perylene dye, ID28, on TiO(2) and of the hole conductor, 2,2'7,7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-MeOTAD), were determined by spectroelectrochemistry. The onset of oxidation of a solid film of spiro-MeOTAD was found to be 0.15 V versus Fc/Fc(+) and extinction coefficients of spiro-MeOTAD(+) were found to be 33 000 M(-1) cm(-1) at 507 nm and 8500 M(-1) cm-' at 690 nm. Electrons in TiO(2) films were shown to alter the ground-state absorption spectra of ID28 attached to TiO(2)-PIA measurements indicated a good contact between ID28 and spiro-MeOTAD for different spiro-MeOTAD concentrations for both 2- and 6-mu m thick TiO(2) films. We discuss the possibility of estimating the quality of pore filling from the positions of absorption peaks. Results suggested that with a spiro-MeOTAD concentration of 300 mg mL(-1) in chlorobenzene, a uniform distribution of spiro-MeOTAD in the pores of the 6-mu m thick TiO(2) film could be achieved.

  • 9. Cappel, Ute B
    et al.
    Bell, Ian M
    Pickard, Laura K
    Removing cosmic ray features from Raman map data by a refined nearest neighbor comparison method as a precursor for chemometric analysis.2010In: Applied Spectroscopy, ISSN 0003-7028, E-ISSN 1943-3530, Vol. 64, no 2, p. 195-200Article in journal (Refereed)
    Abstract [en]

    An algorithm to remove cosmic ray (CR) features from Raman spectra collected in mapping experiments using a charge-coupled device (CCD) is presented. Each spectrum is compared to spectra collected from adjacent points in space using correlation values. The most similar neighbor (MSN) spectrum is selected, offset, and used for identification of CRs. The offset values are defined in terms of the noise level for data with a low signal-to-noise ratio and in terms of the peak height for data with a high signal-to-noise ratio. Scaled intensity values of the MSN spectra are used for replacement of contaminated pixels, allowing for full recovery of underlying spectral features. The algorithm is applicable for any Raman map where the particle sizes within the analyzed mixture are larger than the sampling size or to any other data where the sampling is more frequent than the variation, e.g., time series or temperature profiles. Its application to several maps of pharmaceutical samples is discussed here. With an appropriate offset value for the MSN spectra, no misdetections occur, and all CRs more intense than the offset are removed, which includes the CRs that would have hampered subsequent chemometric analysis by methods such as principal component analysis (PCA).

  • 10. Cappel, Ute B
    et al.
    Daeneke, Torben
    Bach, Udo
    Oxygen-induced doping of spiro-MeOTAD in solid-state dye-sensitized solar cells and its impact on device performance.2012In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 12, no 9, p. 4925-31Article in journal (Refereed)
    Abstract [en]

    Solid state dye-sensitized solar cells (sDSCs) employing the hole conductor 2,2'7,7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-MeOTAD) require the presence of oxygen during fabrication and storage. In this paper, we determine the concentrations of oxidized spiro-MeOTAD within devices under different operating and storage conditions by UV-vis spectroscopy. Relative concentrations of spiro-MeOTAD(+) were found to be greater than 10% after illumination for standard sDSCs, where no chemical dopant had been used in the solar cell fabrication but oxygen and lithium ions were present. We suggest that oxidized spiro-MeOTAD is created as a byproduct of oxygen reduction at the TiO(2) surface during cell illumination. Furthermore, we studied the effect of light soaking under different conditions and associated changes in spiro-MeOTAD(+) concentration on the solar cell measurements. Our findings give insights to photochemical reactions occurring within sDSCs and provide guidelines for which doping levels should be used in device fabrication in absence of oxygen.

  • 11. Cappel, Ute B
    et al.
    Dowland, Simon A
    Reynolds, Luke X
    Dimitrov, Stoichko
    Haque, Saif A
    Charge Generation Dynamics in CdS: P3HT Blends for Hybrid Solar Cells.2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 24, p. 4253-7Article in journal (Refereed)
    Abstract [en]

    Development of design rules for hybrid inorganic-organic solar cells through understanding charge generation and recombination dynamics is an important pathway for the improvement of solar cell conversion efficiencies. In this Letter, we study the dynamics of charge generation in CdS:polymer blends by transient absorption spectroscopy. We show that charge generation following excitation of the inorganic component is highly efficient and can occur up to a few nanoseconds after excitation, allowing for diffusion of charges within the inorganic component to an interface. In contrast, charge generation following excitation of the organic component occurs on subpicosecond time scales but suffers from two loss processes, incomplete exciton dissociation and geminate recombination.

  • 12. Cappel, Ute B
    et al.
    Feldt, Sandra M
    Schöneboom, Jan
    Hagfeldt, Anders
    Boschloo, Gerrit
    The influence of local electric fields on photoinduced absorption in dye-sensitized solar cells.2010In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, no 26, p. 9096-101Article in journal (Refereed)
    Abstract [en]

    The dye-sensitized solar cell (DSC) challenges conventional photovoltaics with its potential for low-cost production and its flexibility in terms of color and design. Transient absorption spectroscopy is widely used to unravel the working mechanism of DSCs. A surprising, unexplained feature observed in these studies is an apparent bleach of the ground-state absorption of the dye, under conditions where the dye is in the ground state. Here, we demonstrate that this feature can be attributed to a change of the local electric field affecting the absorption spectrum of the dye, an effect related to the Stark effect first reported in 1913. We present a method for measuring the effect of an externally applied electric field on the absorption of dye monolayers adsorbed on flat TiO(2) substrates. The measured signal has the shape of the first derivative of the absorption spectra of the dyes and reverses sign along with the reversion of the direction of the change in dipole moment upon excitation relative to the TiO(2) surface. A very similar signal is observed in photoinduced absorption spectra of dye-sensitized TiO(2) electrodes under solar cell conditions, demonstrating that the electric field across the dye molecules changes upon illumination. This result has important implications for the analysis of transient absorption spectra of DSCs and other molecular optoelectronic devices and challenges the interpretation of many previously published results.

  • 13. Cappel, Ute B.
    et al.
    Karlsson, Martin H.
    Pschirer, Neil G.
    Eickemeyer, Felix
    Schoeneboom, Jan
    Erk, Peter
    Boschloo, Gerrit
    Hagfeldt, Anders
    A Broadly Absorbing Perylene Dye for Solid-State Dye-Sensitized Solar Cells2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 33, p. 14595-14597Article in journal (Refereed)
    Abstract [en]

    We present a new perylene sensitizer, ID 176, for dye-sensitized solar cells (DSCs). The dye has the capability for very high photocurrents due to strong absorption from 400 to over 700 rim. Photocurrents Of LIP to 9 mA cm(-2) were achieved in solid-state DSCs employing the hole conductor 2,2’7,7’-tetrakis-(NN-di-p-methoxyphenylamine)-9,9’-spirobifluorene (spiro-MeOTAD), with a conversion efficiency of 3.2%. In contrast, the sensitizer did not perform well in conjunction with liquid iodide/tri-iodide electrolytes, suggesting a difference in the injection and regeneration mechanisms in these two types of dye-sensitized solar cells.

  • 14.
    Cappel, Ute B.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Liu, Peng
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Fredrik O. L.
    Uppsala Univ, Div Mol & Condensed Matter Phys, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Philippe, Bertrand
    Uppsala Univ, Div Mol & Condensed Matter Phys, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Giangrisostomi, Erika
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Lindblad, Andreas
    Uppsala Univ, Div Mol & Condensed Matter Phys, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Rensmo, Hakan
    Uppsala Univ, Div Mol & Condensed Matter Phys, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Electronic Structure Characterization of Cross-Linked Sulfur Polymers2018In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 19, no 9, p. 1041-1047Article in journal (Refereed)
    Abstract [en]

    Cross-linked polymers of elemental sulfur are of potential interest for electronic applications as they enable facile thin-film processing of an abundant and inexpensive starting material. Here, we characterize the electronic structure of a cross-linked sulfur/diisopropenyl benzene (DIB) polymer by a combination of soft and hard X-ray photoelectron spectroscopy (SOXPES and HAXPES). Two different approaches for enhancing the conductivity of the polymer are compared: the addition of selenium in the polymer synthesis and the addition of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) during film preparation. For the former, we observe the incorporation of Se into the polymer structure resulting in a changed valence-band structure. For the latter, a Fermi level shift in agreement with p-type doping of the polymer is observed and also the formation of a surface layer consisting mostly of TFSI anions.

  • 15.
    Cappel, Ute B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, Stockholm, Sweden.
    Liu, Peng
    KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Giangrisostomi, Erika
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kloo, Lars
    KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden.
    Gardner, James M.
    KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Electronic Structure Characterization of Cross-Linked Sulfur Polymers2018In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 19, no 9, p. 1041-1047Article in journal (Refereed)
    Abstract [en]

    Cross-linked polymers of elemental sulfur are of potential interest for electronic applications as they enable facile thin-film processing of an abundant and inexpensive starting material. Here, we characterize the electronic structure of a cross-linked sulfur/diisopropenyl benzene (DIB) polymer by a combination of soft and hard X-ray photoelectron spectroscopy (SOXPES and HAXPES). Two different approaches for enhancing the conductivity of the polymer are compared: the addition of selenium in the polymer synthesis and the addition of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) during film preparation. For the former, we observe the incorporation of Se into the polymer structure resulting in a changed valence-band structure. For the latter, a Fermi level shift in agreement with p-type doping of the polymer is observed and also the formation of a surface layer consisting mostly of TFSI anions.

  • 16. Cappel, Ute B
    et al.
    Moia, Davide
    Bruno, Annalisa
    Vaissier, Valerie
    Haque, Saif A
    Barnes, Piers R F
    Evidence for photo-induced charge separation between dye molecules adsorbed to aluminium oxide surfaces.2016In: Scientific Reports, E-ISSN 2045-2322, Vol. 6, article id 21276Article in journal (Refereed)
    Abstract [en]

    Excited state dynamics and photo-induced charge transfer of dye molecules have been widely studied due to their relevance for organic and dye-sensitised solar cells. Herein, we present a femtosecond transient absorption spectroscopy study of the indolene dye D131 when adsorbed to inert Al2O3 substrates for different surface concentration of the dye. Surprisingly, we find that at high surface concentrations, the first singlet excited state of the dye is converted into a new state with an efficiency of about 80%. We assign the absorption features of this state to the oxidised dye and discuss the possibility of photo-induced charge separation between neighboring dye molecules. Our study is the first to show that this process can be highly efficient without the use of donor and acceptor molecules of different chemical structures.

  • 17. Cappel, Ute B
    et al.
    Plogmaker, Stefan
    Johansson, Erik M J
    Hagfeldt, Anders
    Boschloo, Gerrit
    Rensmo, Håkan
    Energy alignment and surface dipoles of rylene dyes adsorbed to TiO2 nanoparticles.2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 32, p. 14767-74Article in journal (Refereed)
    Abstract [en]

    The energy loss in dye-sensitized solar cells calculated from the energy difference between the lowest electronic transition of the dye and the obtained open-circuit voltage is often 1 eV or even more. To minimize this loss, it is important to accurately determine the energy alignment at the TiO(2)/dye/redox-mediator interface. In this study, we compared the results from electrochemistry and photoelectron spectroscopy for determining the energy alignment of three rylene dyes, two of which absorb relatively far in the red. The trends observed with the methods were different, as in the former, the energy alignment is measured relative to an external reference and includes contributions from solvent reorganization energies, while in the latter, it is measured relative to the energetics of the TiO(2) and is lacking such contributions. The influence of the dyes' dipole moments on the energetics of the TiO(2) was also measured and explained some of the differences in trends. Finally, we compared the injection efficiencies of the two red-absorbing dyes and found that the differences in injection efficiencies can be better explained using the energy alignment determined from photoelectron spectroscopy. This shows that the method for measuring the energetics of a DSC should be chosen according to what process one intends to study.

  • 18. Cappel, Ute B
    et al.
    Plogmaker, Stefan
    Terschlüsen, Joachim A
    Leitner, Torsten
    Johansson, Erik M J
    Edvinsson, Tomas
    Sandell, Anders
    Karis, Olof
    Siegbahn, Hans
    Svensson, Svante
    Mårtensson, Nils
    Rensmo, Håkan
    Söderström, Johan
    Electronic structure dynamics in a low bandgap polymer studied by time-resolved photoelectron spectroscopy.2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 31, p. 21921-9Article in journal (Refereed)
    Abstract [en]

    Means to measure the temporal evolution following a photo-excitation in conjugated polymers are a key for the understanding and optimization of their function in applications such as organic solar cells. In this paper we study the electronic structure dynamics by direct pump-probe measurements of the excited electrons in such materials. Specifically, we carried out a time-resolved photoelectron spectroscopy (TRPES) study of the polymer PCPDTBT by combining an extreme ultraviolet (XUV) high harmonic generation source with a time-of-flight spectrometer. After excitation to either the 1st excited state or to a higher excited state, we follow how the electronic structure develops and relaxes on the electron binding energy scale. Specifically, we follow a less than 50 fs relaxation of the higher exited state and a 10 times slower relaxation of the 1st excited state. We corroborate the results using DFT calculations. Our study demonstrates the power of TRPES for studying photo-excited electron energetics and dynamics of solar cell materials.

  • 19. Cappel, Ute B.
    et al.
    Smeigh, Amanda L.
    Plogmaker, Stefan
    Johansson, Erik M. J.
    Rensmo, Hakan
    Hammarstrom, Leif
    Hagfeldt, Anders
    Boschloo, Gerrit
    Characterization of the Interface Properties and Processes in Solid State Dye-Sensitized Solar Cells Employing a Perylene Sensitizer2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 10, p. 4345-4358Article in journal (Refereed)
    Abstract [en]

    We recently reported on a perylene sensitizer, ID176, which performs much better in solid state dye-sensitized solar cells than in those using liquid electrolytes with iodide/tri-iodide as the redox couple (J. Phys. Chem. C 2009, 113, 14595-14597). Here, we present a characterization of the sensitizer and of the TiO2/dye interface by UV-visible absorption and fluorescence spectroscopy, spectroelectrochemistry, photoelectron spectroscopy, electroabsorption spectroscopy, photoinduced absorption spectroscopy, and femtosecond transient absorption measurements. We report that the absorption spectrum of the sensitizer is red-shifted by addition of lithium ions to the surface due to a downward shift of the excited state level of the sensitizer, which is of the same order of magnitude as the downward shift of the titanium dioxide conduction band edge. Results from photoelectron spectroscopy and electrochemistry suggest that the excited state is largely located below the conduction band edge of TiO2 but that there are states in the band gap of TiO2 which might be available for photoinduced electron injection. The sensitizer was able to efficiently inject into TiO2, when a lithium salt was present on the surface, while injection was much less effective in the absence of lithium ions or in the presence of solvent. In the presence of the hole conductor 2,2’,7,7’-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9’-spirobifluorene (spiro-MeOTAD) and LiTFSI, charge separation was monitored by the emergence of a Stark shift of the dye in transient absorption spectra, and both injection and regeneration appear to be completed within 1 ps. Regeneration by spiro-MeOTAD is therefore several orders of magnitude faster than regeneration by iodide, and ID176 can even be photoreduced by spiro-MeOTAD.

  • 20.
    Cappel, Ute B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Johansson, Fredrik O. L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Aitola, Kerttu
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Giangrisostomi, Erika
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Leitner, Torsten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Foehlisch, Alexander
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.;Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Uppsala Berlin Joint Lab Next Generat Photoelectr, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Rensmo, Håkan
    Partially Reversible Photoinduced Chemical Changes in a Mixed-Ion Perovskite Material for Solar Cells2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 40, p. 34970-34978Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites have emerged as materials of high interest for solar energy-to-electricity conversion, and in particular, the use of mixed-ion structures has led to high power conversion efficiencies and improved stability. For this reason, it is important to develop means to obtain atomic level understanding of the photoinduced behavior of these materials including processes such as photoinduced phase separation and ion migration. In this paper, we implement a new methodology combining visible laser illumination of a mixed-ion perovskite ((FAP-bI(3))(0.85)(MAPbBr(3))(0.15)) with the element specificity and chemical sensitivity of core-level photoelectron spectroscopy. By carrying out measurements at a synchrotron beamline optimized for low X-ray fluxes, we are able to avoid sample changes due to X-ray illumination and are therefore able to monitor what sample changes are induced by visible illumination only. We find that laser illumination causes partially reversible chemistry in the surface region, including enrichment of bromide at the surface, which could be related to a phase separation into bromide- and iodide-rich phases. We also observe a partially reversible formation of metallic lead in the perovskite structure. These processes occur on the time scale of minutes during illumination. The presented methodology has a large potential for understanding light-induced chemistry in photoactive materials and could specifically be extended to systematically study the impact of morphology and composition on the photostability of metal halide perovskites.

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  • 21. Cappel, Ute B
    et al.
    Svanström, Sebastian
    Lanzilotto, Valeria
    Johansson, Fredrik O L
    Aitola, Kerttu
    Philippe, Bertrand
    Giangrisostomi, Erika
    Ovsyannikov, Ruslan
    Leitner, Torsten
    Föhlisch, Alexander
    Svensson, Svante
    Mårtensson, Nils
    Boschloo, Gerrit
    Lindblad, Andreas
    Rensmo, Håkan
    Partially Reversible Photoinduced Chemical Changes in a Mixed-Ion Perovskite Material for Solar Cells.2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 40, p. 34970-34978Article in journal (Refereed)
    Abstract [en]

    ) with the element specificity and chemical sensitivity of core-level photoelectron spectroscopy. By carrying out measurements at a synchrotron beamline optimized for low X-ray fluxes, we are able to avoid sample changes due to X-ray illumination and are therefore able to monitor what sample changes are induced by visible illumination only. We find that laser illumination causes partially reversible chemistry in the surface region, including enrichment of bromide at the surface, which could be related to a phase separation into bromide- and iodide-rich phases. We also observe a partially reversible formation of metallic lead in the perovskite structure. These processes occur on the time scale of minutes during illumination. The presented methodology has a large potential for understanding light-induced chemistry in photoactive materials and could specifically be extended to systematically study the impact of morphology and composition on the photostability of metal halide perovskites.

  • 22. D'Amario, Luca
    et al.
    Jiang, Roger
    Cappel, Ute B.
    Gibson, Elizabeth A.
    Boschloo, Gerrit
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Rensmo, Hakan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Hammarstrom, Leif
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Chemical and Physical Reduction of High Valence Ni States in Mesoporous NiO Film for Solar Cell Application2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 39, p. 33470-33477Article in journal (Refereed)
    Abstract [en]

    The most common material for dye-sensitized photocathodes is mesoporous NiO. We transformed the usual brownish NiO to be more transparent by reducing high valence Ni impurities. Two pretreatment methods have been used: chemical reduction by NaBH4 and thermal reduction by heating. The power conversion efficiency of the cell was increased by 33% through chemical treatment, and an increase in open-circuit voltage from 105 to 225 mV was obtained upon heat treatment. By optical spectroelectrochemistry, we could identify two species with characteristically different spectra assigned to Ni3+ and Ni4+. We suggest that the reduction of surface Ni3+ and Ni (4+) to Ni (2+) decreases the recombination reaction between holes on the NiO surface with the electrolyte. It also keeps the dye firmly on the surface, building a barrier for electrolyte recombination. This causes an increase in open-circuit photovoltage for the treated film.

  • 23. Dowland, Simon A.
    et al.
    Reynolds, Luke X.
    MacLachlan, Andrew
    Cappel, Ute B.
    Haque, Saif A.
    Photoinduced electron and hole transfer in CdS:P3HT nanocomposite films: effect of nanomorphology on charge separation yield and solar cell performance2013In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, no 44, p. 13896-13901Article in journal (Refereed)
    Abstract [en]

    The influence of morphology on the photophysical properties of blend films containing in situ grown CdS and poly(3-hexylthiophene-2,5-diyl) (P3HT), fabricated utilising a metal xanthate single source precursor, is reported. A combination of transient absorption spectroscopy (TAS), transmission electron microscopy (TEM) and photovoltaic device measurements are employed to study the relationship between the efficiency of charge separation, photocurrent generation and thin film morphology. We identify that a significant proportion of the extractable charge originates from the direct excitation of CdS followed by hole-transfer to the P3HT polymer. The yield of this hole-transfer step from the inorganic CdS to the organic polymer is largely unaffected by the film’s nanomorphology, while the dissociation of P3HT excitons into free charges at the CdS:P3HT interface is found to be strongly dependent on this parameter with high yields of charge transfer only being achieved at high CdS loadings. The present study elucidates design rules for the optimization of hybrid inorganic-organic solar energy conversion devices.

  • 24. Erbing, Axel
    et al.
    Philippe, Bertrand
    Park, B. -W
    Cappel, Ute B.
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Rensmo, H.
    Odelius, M.
    Spatial microheterogeneity in the valence band of mixed halide hybrid perovskite materials2022In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 13, no 32, p. 9285-9294Article in journal (Refereed)
    Abstract [en]

    The valence band of lead halide hybrid perovskites with a mixed I/Br composition is investigated using electronic structure calculations and complementarily probed with hard X-ray photoelectron spectroscopy. In the latter, we used high photon energies giving element sensitivity to the heavy lead and halide ions and we observe distinct trends in the valence band as a function of the I : Br ratio. Through electronic structure calculations, we show that the spectral trends with overall composition can be understood in terms of variations in the local environment of neighboring halide ions. From the computational model supported by the experimental evidence, a picture of the microheterogeneity in the valence band maximum emerges. The microheterogeneity in the valence band suggests that additional charge transport mechanisms might be active in lead mixed halide hybrid perovskites, which could be described in terms of percolation pathways.

  • 25.
    Erbing, Axel
    et al.
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Park, Byung-wook
    Ulsan Natl Inst Sci & Technol, Dept Energy & Chem Engn, 50 UNIST Gil, Ulsan 44919, South Korea..
    Cappel, Ute B.
    KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden..
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Odelius, Michael
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Spatial microheterogeneity in the valence band of mixed halide hybrid perovskite materials2022In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 13, no 32, p. 9285-9294Article in journal (Refereed)
    Abstract [en]

    The valence band of lead halide hybrid perovskites with a mixed I/Br composition is investigated using electronic structure calculations and complementarily probed with hard X-ray photoelectron spectroscopy. In the latter, we used high photon energies giving element sensitivity to the heavy lead and halide ions and we observe distinct trends in the valence band as a function of the I : Br ratio. Through electronic structure calculations, we show that the spectral trends with overall composition can be understood in terms of variations in the local environment of neighboring halide ions. From the computational model supported by the experimental evidence, a picture of the microheterogeneity in the valence band maximum emerges. The microheterogeneity in the valence band suggests that additional charge transport mechanisms might be active in lead mixed halide hybrid perovskites, which could be described in terms of percolation pathways.

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    fulltext
  • 26. Feldt, Sandra M.
    et al.
    Cappel, Ute B.
    Johansson, Erik M. J.
    Boschloo, Gerrit
    Hagfeldt, Anders
    Characterization of Surface Passivation by Poly(methylsiloxane) for Dye-Sensitized Solar Cells Employing the Ferrocene Redox Couple2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 23, p. 10551-10558Article in journal (Refereed)
    Abstract [en]

    One-electron outer-sphere redox couples, such as ferrocene/ferrocenium, are an interesting alternative to the iodide/triiodide redox couple that is normally employed in dye-sensitized solar cells (DSCs) because they should reduce the driving force needed to regenerate the dye. Unfortunately, one-electron redox couples also show enhanced recombination with photoinjected electrons, and methods to inhibit this recombination are needed for functioning DSCs. In this study, dye-sensitized titanium dioxide surfaces were passivated by a trichloromethylsilane reaction in order to decrease the fast recombination rates when using the ferrocene redox couple. The formation and binding of poly(methylsiloxane) on the dye-sensitized TiO(2) surface was verified with infrared spectroscopy and photoelectron spectroscopy. Photoelectrochemical characterization of the silanization method showed that the treatment decreased the recombination rate of photoinjected electrons with ferrocenium and thereby improved the efficiency of the DSC. Transient absorption spectroscopy revealed, however, that the poly(methylsiloxane) coatings slowed down the regeneration of the oxidized dye by the ferrocene and prevented the regeneration of some of the dye molecules.

  • 27.
    Franchi, Daniele
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Inst Chem Organometall Cpds CNR ICCOM, I-50019 Sesto Fiorentino, Italy..
    Leandri, Valentina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Pizzichetti, Angela Raffaella Pia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Xu, Bo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH). Uppsala Univ, Ctr Mol Devices, Dept Chem, Div Phys Chem,Angstrom Lab, SE-75120 Uppsala, Sweden..
    Hao, Yan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Zhang, Wei
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sloboda, Tamara
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Svanstrom, Sebastian
    Uppsala Univ, Dept Phys & Astron, Div Xray Photon Sci, SE-75120 Uppsala, Sweden..
    Cappel, Ute B.
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Westlake Univ, Ctr Artificial Photosynth Solar Fuels, Sch Sci, Hangzhou 310024, Peoples R China..
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Effect of the Ancillary Ligand on the Performance of Heteroleptic Cu(I) Diimine Complexes as Dyes in Dye-Sensitized Solar Cells2022In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 5, no 2, p. 1460-1470Article in journal (Refereed)
    Abstract [en]

    A series of heteroleptic Cu(I) diimine complexes with different ancillary ligands and 6,6'-dimethyl-2,2'-bipyridine-4,4'-dibenzoic acid (dbda) as the anchoring ligand were selfassembled on TiO2 surfaces and used as dyes for dye-sensitized solar cells (DSSCs). The binding to the TiO2 surface was studied by hard X-ray photoelectron spectroscopy for a brominecontaining complex, confirming the complex formation. The performance of all complexes was assessed and rationalized on the basis of their respective ancillary ligand. The DSSC photocurrent-voltage characteristics, incident photon-to-current conversion efficiency (IPCE) spectra, and calculated lowest unoccupied molecular orbital (LUMO) distributions collectively show a push-pull structural dye design, in which the ancillary ligand exhibits an electron-donating effect that can lead to improved solar cell performance. By analyzing the optical properties of the dyes and their solar cell performance, we can conclude that the presence of ancillary ligands with bulky substituents protects the Cu(I) metal center from solvent coordination constituting a critical factor in the design of efficient Cu(I)-based dyes. Moreover, we have identified some components in the I-/I-3(-)-based electrolyte that causes dissociation of the ancillary ligand, i.e., TiO2 photoelectrode bleaching. Finally, the detailed studies on one of the dyes revealed an electrolyte-dye interaction, leading to a dramatic change of the dye properties when adsorbed on the TiO2 surface.

  • 28.
    Franchi, Daniele
    et al.
    Inst Chem Organometall Cpds CNR ICCOM, I-50019 Sesto Fiorentino, Italy.;KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem, Div Organ Chem, SE-10044 Stockholm, Sweden..
    Leandri, Valentina
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Pizzichetti, Angela Raffaella Pia
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Xu, Bo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Hao, Yan
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Zhang, Wei
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Sloboda, Tamara
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Cappel, Ute B.
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Kloo, Lars
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Sun, Licheng
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem, Div Organ Chem, SE-10044 Stockholm, Sweden.;Westlake Univ, Ctr Artificial Photosynth Solar Fuels, Sch Sci, Hangzhou 310024, Peoples R China..
    Gardner, James M.
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Effect of the Ancillary Ligand on the Performance of Heteroleptic Cu(I) Diimine Complexes as Dyes in Dye-Sensitized Solar Cells2022In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 5, no 2, p. 1460-1470Article in journal (Refereed)
    Abstract [en]

    A series of heteroleptic Cu(I) diimine complexes with different ancillary ligands and 6,6'-dimethyl-2,2'-bipyridine-4,4'-dibenzoic acid (dbda) as the anchoring ligand were selfassembled on TiO2 surfaces and used as dyes for dye-sensitized solar cells (DSSCs). The binding to the TiO2 surface was studied by hard X-ray photoelectron spectroscopy for a brominecontaining complex, confirming the complex formation. The performance of all complexes was assessed and rationalized on the basis of their respective ancillary ligand. The DSSC photocurrent-voltage characteristics, incident photon-to-current conversion efficiency (IPCE) spectra, and calculated lowest unoccupied molecular orbital (LUMO) distributions collectively show a push-pull structural dye design, in which the ancillary ligand exhibits an electron-donating effect that can lead to improved solar cell performance. By analyzing the optical properties of the dyes and their solar cell performance, we can conclude that the presence of ancillary ligands with bulky substituents protects the Cu(I) metal center from solvent coordination constituting a critical factor in the design of efficient Cu(I)-based dyes. Moreover, we have identified some components in the I-/I-3(-)-based electrolyte that causes dissociation of the ancillary ligand, i.e., TiO2 photoelectrode bleaching. Finally, the detailed studies on one of the dyes revealed an electrolyte-dye interaction, leading to a dramatic change of the dye properties when adsorbed on the TiO2 surface.

    Download full text (pdf)
    fulltext
  • 29.
    Garcia Fernandez, Alberto
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Kammlander, Birgit
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Riva, Stefania
    Division of X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, Uppsala, 751 20, Sweden.
    Kühn, Danilo
    Institute Methods and Instrumentation for Synchrotron Radiation Research PSISRR, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, Berlin, 12489, Germany.
    Svanström, Sebastian
    Division of X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, Uppsala, 751 20, Sweden.
    Rensmo, Håkan
    Division of X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, Uppsala, 751 20, Sweden.
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Interface Energy Alignment between Lead Halide Perovskite Single Crystals and TIPS-Pentacene2023In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 62, no 38, p. 15412-15420Article in journal (Refereed)
    Abstract [en]

    At present, there is a huge development in optoelectronic applications using lead halide perovskites. Considering that device performance is largely governed by the transport of charges across interfaces and, therefore, the interfacial electronic structure, fundamental investigations of perovskite interfaces are highly necessary. In this study, we use high-resolution soft X-ray photoelectron spectroscopy based on synchrotron radiation to explore the interfacial energetics for the molecular layer of TIPS-pentacene and lead halide perovskite single crystals. We perform ultrahigh vacuum studies on multiple thicknesses of an in situ formed interface of TIPS-pentacene with four different in situ cleaved perovskite single crystals (MAPbI3, MAPbBr3, FAPbBr3, and CsxFA1-xPbBryI3-y). Our findings reveal a substantial shift of the TIPS-pentacene energy levels toward higher binding energies with increasing thickness, while the perovskite energy levels remain largely unaffected regardless of their composition. These shifts can be interpreted as band bending in the TIPS-pentacene, and such effects should be considered when assessing the energy alignment at perovskite/organic transport material interfaces. Furthermore, we were able to follow a reorganization on the MAPbI3 surface with the transformation of the surface C 1s into bulk C 1s.

  • 30.
    Garcia Fernandez, Alberto
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Svanström, Sebastian
    Uppsala Univ, Dept Phys & Astron, Div Xray Photon Sci, Condensed Matter Phys Energy Mat, Box 516, SE-75120 Uppsala, Sweden..
    Sterling, Cody M.
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, S-10691 Stockholm, Sweden..
    Gangan, Abhijeet
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, S-10691 Stockholm, Sweden..
    Erbing, Axel
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, S-10691 Stockholm, Sweden..
    Kamal, Chinnathambi
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, S-10691 Stockholm, Sweden.;Raja Ramanna Ctr Adv Technol, Theory & Simulat Lab, HRDS, Indore 452013, Madhya Pradesh, India.;Homi Bhabha Natl Inst, Training Sch Complex, Mumbai 400094, Maharashtra, India..
    Sloboda, Tamara
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Kammlander, Birgit
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Man, Gabriel J.
    Uppsala Univ, Dept Phys & Astron, Div Xray Photon Sci, Condensed Matter Phys Energy Mat, Box 516, SE-75120 Uppsala, Sweden..
    Rensmo, Håkan
    Uppsala Univ, Dept Phys & Astron, Div Xray Photon Sci, Condensed Matter Phys Energy Mat, Box 516, SE-75120 Uppsala, Sweden..
    Odelius, Michael
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, S-10691 Stockholm, Sweden..
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Experimental and Theoretical Core Level and Valence Band Analysis of Clean Perovskite Single Crystal Surfaces2022In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 18, no 13, article id 2106450Article in journal (Refereed)
    Abstract [en]

    A detailed understanding of the surface and interface properties of lead halide perovskites is of interest for several applications, in which these materials may be used. To develop this understanding, the study of clean crystalline surfaces can be an important stepping stone. In this work, the surface properties and electronic structure of two different perovskite single crystal compositions (MAPbI(3) and Cs(x)FA(1-)(x)PbI(3)) are investigated using synchrotron-based soft X-ray photoelectron spectroscopy (PES), molecular dynamics simulations, and density functional theory. The use of synchrotron-based soft X-ray PES enables high surface sensitivity and nondestructive depth-profiling. Core level and valence band spectra of the single crystals are presented. The authors find two carbon 1s contributions at the surface of MAPbI(3) and assign these to MA(+) ions in an MAI-terminated surface and to MA(+) ions below the surface. It is estimated that the surface is predominantly MAI-terminated but up to 30% of the surface can be PbI2-terminated. The results presented here can serve as reference spectra for photoelectron spectroscopy investigations of technologically relevant polycrystalline thin films, and the findings can be utilized to further optimize the design of device interfaces.

  • 31.
    Garcia-Ben, Javier
    et al.
    Univ A Coruna, Ctr Investigac Cient Avanzadas CICA, Quimolmat, Rua Carballeiras, La Coruna 15071, Spain.;Univ A Coruna, Dept Quim, Fac Ciencias, Campus Zapateira, La Coruna 15008, Spain..
    Garcia Fernandez, Alberto
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Dafonte-Rodriguez, Pedro
    Univ A Coruna, Ctr Investigac Cient Avanzadas CICA, Quimolmat, Rua Carballeiras, La Coruna 15071, Spain.;Univ A Coruna, Dept Quim, Fac Ciencias, Campus Zapateira, La Coruna 15008, Spain..
    Delgado-Ferreiro, Ignacio
    Univ A Coruna, Ctr Investigac Cient Avanzadas CICA, Quimolmat, Rua Carballeiras, La Coruna 15071, Spain.;Univ A Coruna, Dept Quim, Fac Ciencias, Campus Zapateira, La Coruna 15008, Spain..
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Castro-Garcia, Socorro
    Univ A Coruna, Ctr Investigac Cient Avanzadas CICA, Quimolmat, Rua Carballeiras, La Coruna 15071, Spain.;Univ A Coruna, Dept Quim, Fac Ciencias, Campus Zapateira, La Coruna 15008, Spain..
    Sanchez-Andujar, Manuel
    Univ A Coruna, Ctr Investigac Cient Avanzadas CICA, Quimolmat, Rua Carballeiras, La Coruna 15071, Spain.;Univ A Coruna, Dept Quim, Fac Ciencias, Campus Zapateira, La Coruna 15008, Spain..
    Manuel Bermudez-Garcia, Juan
    Univ A Coruna, Ctr Investigac Cient Avanzadas CICA, Quimolmat, Rua Carballeiras, La Coruna 15071, Spain.;Univ A Coruna, Dept Quim, Fac Ciencias, Campus Zapateira, La Coruna 15008, Spain..
    Antonia Senaris-Rodriguez, Maria
    Univ A Coruna, Ctr Investigac Cient Avanzadas CICA, Quimolmat, Rua Carballeiras, La Coruna 15071, Spain.;Univ A Coruna, Dept Quim, Fac Ciencias, Campus Zapateira, La Coruna 15008, Spain..
    Narrowing the tolerance factor limits for hybrid organic-inorganic dicyanamide-perovskites2022In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 316, p. 123635-, article id 123635Article in journal (Refereed)
    Abstract [en]

    In this work we focus in setting the limits of the tolerance factor and the size of the A-cations that stabilize the perovskite structure in hybrid dicyanamide compounds [A][Mn(dca)3]. For this purpose, we propose an alter-native, simple approach to calculate a more realistic effective ionic radius for the large and anisotropic A-cations often present in these type of compounds. We test the proposed procedure by analysing the crystal structures of [A][Mn(dca)3] dicyanamide hybrids reported in the literature and recalculating the tolerance factors of such compounds, as well as by preparing five new [A][Mn(dca)3] members, discussing also the influence of the A -cation shape in the stability limits of the perovskite structure. Interestingly, such methodology is not only useful to develop new compounds of the emerging family of (multi)functional multi(stimuli)-responsive dicyanamide materials but can also be applied to other hybrid organic-inorganic perovskites and related materials.

  • 32.
    Garcia-Fernandez, Alberto
    et al.
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, S-10044 Stockholm, Sweden..
    Kammlander, Birgit
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, S-10044 Stockholm, Sweden..
    Riva, Stefania
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Kuehn, Danilo
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, D-12489 Berlin, Germany..
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala Univ, Dept Phys & Astron, Div Xray Photon Sci, S-75120 Uppsala, Sweden..
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Cappel, Ute B.
    Interface Energy Alignment between Lead Halide Perovskite Single Crystals and TIPS-Pentacene2023In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 62, no 38, p. 15412-15420Article in journal (Refereed)
    Abstract [en]

    At present, there is a huge development in optoelectronic applications using lead halide perovskites. Considering that device performance is largely governed by the transport of charges across interfaces and, therefore, the interfacial electronic structure, fundamental investigations of perovskite interfaces are highly necessary. In this study, we use high-resolution soft X-ray photoelectron spectroscopy based on synchrotron radiation to explore the interfacial energetics for the molecular layer of TIPS-pentacene and lead halide perovskite single crystals. We perform ultrahigh vacuum studies on multiple thicknesses of an in situ formed interface of TIPS-pentacene with four different in situ cleaved perovskite single crystals (MAPbI(3), MAPbBr(3), FAPbBr(3), and Cs(x)FA(1-x)PbBr(y)I(3-y)). Our findings reveal a substantial shift of the TIPS-pentacene energy levels toward higher binding energies with increasing thickness, while the perovskite energy levels remain largely unaffected regardless of their composition. These shifts can be interpreted as band bending in the TIPS-pentacene, and such effects should be considered when assessing the energy alignment at perovskite/organic transport material interfaces. Furthermore, we were able to follow a reorganization on the MAPbI3 surface with the transformation of the surface C 1s into bulk C 1s.

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  • 33.
    García-Fernández, Alberto
    et al.
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, S-10044 Stockholm, Sweden.
    Kammlander, Birgit
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials. KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, S-10044 Stockholm, Sweden..
    Riva, Stefania
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials. KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, S-10044 Stockholm, Sweden.
    Composition dependence of X-ray stability and degradation mechanisms at lead halide perovskite single crystal surfaces2024In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 26, no 2, p. 1000-1010Article in journal (Refereed)
    Abstract [en]

    The multiple applications of lead halide perovskite materials and the extensive use of X-ray based techniques to characterize them highlight a need to understand their stability under X-ray irradiation. Here, we present a study where the X-ray stability of five different lead halide perovskite compositions (MAPbI3, MAPbCl3, MAPbBr3, FAPbBr3, CsPbBr3) was investigated using photoelectron spectroscopy. To exclude effects of thin film formation on the observed degradation behaviors, we studied clean surfaces of single crystals. Different X-ray resistance and degradation mechanisms were observed depending on the crystal composition. Overall, perovskites based on the MA+ cation were found to be less stable than those based on FA+ or Cs+. Metallic lead formed most easily in the chloride perovskite, followed by bromide, and only very little metallic lead formation was observed for MAPbI3. MAPbI3 showed one main degradation process, which was the radiolysis of MAI. Multiple simultaneous degradation processes were identified for the bromide compositions. These processes include ion migration towards the perovskite surface and the formation of volatile and solid products in addition to metallic lead. Lastly, CsBr formed as a solid degradation product on the surface of CsPbBr3.

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  • 34. Giangrisostomi, Erika
    et al.
    Ovsyannikov, Ruslan
    Sorgenfrei, Florian
    Zhang, Teng
    Lindblad, Andreas
    Sassa, Yasmine
    Cappel, Ute B.
    Leitner, Torsten
    Mitzner, Rolf
    Svensson, Svante
    Martensson, Nils
    Foehlisch, Alexander
    Low Dose Photoelectron Spectroscopy at BESSY II: Electronic structure of matter in its native state2018In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, no SI, p. 68-78Article in journal (Refereed)
    Abstract [en]

    The implementation of a high-transmission, angular-resolved time-of-Right electron spectrometer with a 1.25 MHz pulse selector at the PM4 soft X-ray dipole beamline of the synchrotron BESSY II creates unique capabilities to inquire electronic structure via photoelectron spectroscopy with a minimum of radiation dose. Solid-state samples can be prepared and characterized with standard UHV techniques and rapidly transferred from various preparation chambers to a 4-axis temperature-controlled measurement stage. A synchronized MHz laser system enables excited-state characterization and dynamical studies starting from the picosecond timescale. This article introduces the principal characteristics of the PM4 beamline and LowDosePES end-station. Recent results from graphene, an organic hole transport material for solar cells and the transition metal dichalcogenide MoS2 are presented to demonstrate the instrument performances. (C) 2017 The Authors. Published by Elsevier B.V.

  • 35.
    Giangrisostomi, Erika
    et al.
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-72489 Berlin, Germany..
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-72489 Berlin, Germany..
    Sorgenfrei, Florian
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Sassa, Yasmine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Leitner, Torsten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Mitzner, Rolf
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-72489 Berlin, Germany..
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Foehlisch, Alexander
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-72489 Berlin, Germany.;Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Low Dose Photoelectron Spectroscopy at BESSY II: Electronic structure of matter in its native state2018In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 68-78Article in journal (Refereed)
    Abstract [en]

    The implementation of a high-transmission, angular-resolved time-of-Right electron spectrometer with a 1.25 MHz pulse selector at the PM4 soft X-ray dipole beamline of the synchrotron BESSY II creates unique capabilities to inquire electronic structure via photoelectron spectroscopy with a minimum of radiation dose. Solid-state samples can be prepared and characterized with standard UHV techniques and rapidly transferred from various preparation chambers to a 4-axis temperature-controlled measurement stage. A synchronized MHz laser system enables excited-state characterization and dynamical studies starting from the picosecond timescale. This article introduces the principal characteristics of the PM4 beamline and LowDosePES end-station. Recent results from graphene, an organic hole transport material for solar cells and the transition metal dichalcogenide MoS2 are presented to demonstrate the instrument performances. (C) 2017 The Authors. Published by Elsevier B.V.

    Download full text (pdf)
    fulltext
  • 36. Hagfeldt, A.
    et al.
    Cappel, U. B.
    Boschloo, G.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Pettersson, H.
    Gibson, E. A.
    Mesoporous dye-sensitized solar cells2012In: Reference Module in Earth Systems and Environmental Sciences, Elsevier, 2012, Vol. 1, p. 481-496Chapter in book (Other academic)
    Abstract [en]

    Photovoltaics, or solar cells, are fast growing both with regards to industrialization and research. Globally, the total PV installation is around 40 GW and an annual growth rate of 45% has been experienced over recent years. In the comparison between different photovoltaic technologies a figure of merit is the production cost per peak watt of solar electricity produced. For so called second generation thin film solar cells production costs down to and even below 1 $/W-1 peak are reported. To be competitive with conventional energy sources for large-scale electricity production new PV technologies need to aim at production costs below 0.5 $/W-1 peak. The dye-sensitized solar cell (DSC) is a molecular solar cell technology which have the potential to achieve production costs below 0.5 $/W-1 peak. DSC is based on molecular and nanometer-scale components. Record cell efficiencies of 12%, promising stability data and means of energy efficient production methods have been accomplished. As selling points for the DSC technology the prospect of low-cost investments and fabrication are key features. DSCs offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. This chapter describes the basic principles of the operation of DSC, the state-of-the-art, the materials development that is currently taking place as well as the potentials for future development.

  • 37. Hagfeldt, Anders
    et al.
    Cappel, U.B.
    Boschloo, G.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Dalian University of Technology (DUT), Dalian 116012, China.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Pettersson, H.
    Gibson, E.A.
    Dye-sensitized Photoelectrochemical Cells2012In: Practical Handbook of Photovoltaics Findamentals and Applications, 2nd Edition / [ed] A. McEvoy, T. Markvart, L.Castaner, Oxford: Academic Press, 2012, 2, p. 479-542Chapter in book (Refereed)
    Abstract [en]

    As part of the growing sustainable and renewable energy movement, the design, manufacture and use of photovoltaic devices is increasing in pace and frequency. The Handbook of Photovoltaics will be a 'benchmark' publication for those involved in the design, manufacture and use of these devices. The Handbook covers the principles of solar cell function, the raw materials, photovoltaic systems, standards, calibration, testing, economics and case studies. The editors have assembled a cast of internationally-respected contributors from industry and academia. The report is essential reading for: Physicists, electronic engineers, designers of systems, installers, architects, policy-makers relating to photovoltaics.

  • 38.
    Haydous, Fatima
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    The impact of ligands on the synthesis and application of metal halide perovskite nanocrystals2021In: Journal of Materials Chemistry A, ISSN 2050-7488, E-ISSN 2050-7496, Vol. 9, no 41, p. 23419-23443Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites have emerged as attractive materials for use in solar cells, light emitting diodes and other optoelectronic devices, mainly due to their impressive charge transport properties, strong light absorption, long carrier diffusion lengths and long excited state lifetime. The extensive research on these materials has paved the way for a new class of materials: metal halide perovskite nanocrystals (NCs). Due to their high photoluminescence quantum yield and narrow emission that can be tuned by size and compositional variations, perovskite NCs are considered to be ideal candidates compared to traditional quantum dots. With the growing interest in these materials and the current challenges in their commercialization, this review aims mainly to provide the necessary understanding of the influence of capping ligands on the synthesis and application of perovskite NCs. The different synthetic approaches and the role of ligands in determining the morphological and optical properties of the resulting NCs will be discussed. Thereafter, we review the advances in understanding the surface chemistry and ligation in the metal halide perovskite NCs. Lastly, we review the ligand exchange and management processes that are shown to be beneficial in improving the performance and stability of perovskite nanocrystal films for optoelectronic applications.

  • 39.
    Hultqvist, Adam
    et al.
    Uppsala Univ, Dept Mat Sci, S-75103 Uppsala, Sweden..
    Jacobsson, T. Jesper
    Uppsala Univ, Dept Chem Angstrom, S-75103 Uppsala, Sweden.;Helmholtz Ctr Berlin, Div Renewable Energies, D-14109 Berlin, Germany..
    Svanström, Sebastian
    Uppsala Univ, Dept Phys & Astron, S-75120 Uppsala, Sweden..
    Edoff, Marika
    Uppsala Univ, Dept Mat Sci, S-75103 Uppsala, Sweden..
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Rensmo, Håkan
    Uppsala Univ, Dept Phys & Astron, S-75120 Uppsala, Sweden..
    Johansson, Erik M. J.
    Uppsala Univ, Dept Chem Angstrom, S-75103 Uppsala, Sweden..
    Boschloo, Gerrit
    Uppsala Univ, Dept Chem Angstrom, S-75103 Uppsala, Sweden..
    Torndahl, Tobias
    Uppsala Univ, Dept Mat Sci, S-75103 Uppsala, Sweden..
    SnOx Atomic Layer Deposition on Bare Perovskite-An Investigation of Initial Growth Dynamics, Interface Chemistry, and Solar Cell Performance2021In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 4, no 1, p. 510-522Article in journal (Refereed)
    Abstract [en]

    High-end organic-inorganic lead halide perovskite semitransparent p-i-n solar cells for tandem applications use a phenyl-C-61-butyric acid methyl ester (PCBM)/atomic layer deposition (ALD)-SnOx electron transport layer stack. Omitting the PCBM would be preferred for manufacturing, but has in previous studies on (FA,MA)Pb(Br,I)(3) and (Cs,FA)Pb(Br,I)(3) and in this study on Cs(0)(.0)(5)FA(0.79)MA(0.16)PbBr(0.51)I(2.49) (perovskite) led to poor solar cell performance because of a bias-dependent light-generated current. A direct ALD-SnOx exposure was therefore suggested to form a nonideal perovskite/SnOx interface that acts as a transport barrier for the light-generated current. To further investigate the interface formation during the initial ALD SnOx growth on the perovskite, the mass dynamics of monitor crystals coated by partial p-i-n solar cell stacks were recorded in situ prior to and during the ALD using a quartz crystal microbalance. Two major finds were made. A mass loss was observed prior to ALD for growth temperatures above 60 degrees C, suggesting the decomposition of the perovskite. In addition, a mostly irreversible mass gain was observed during the first exposure to the Sn precursor tetrakis(dimethylamino)tin(IV) that is independent of growth temperature and that disrupts the mass gain of the following 20-50 ALD cycles. The chemical environments of the buried interface were analyzed by soft and hard X-ray photoelectron spectroscopy for a sample with 50 ALD cycles of SnOx on the perovskite. Although measurements on the perovskite bulk below and the SnOx film above did not show chemical changes, additional chemical states for Pb, Br, and N as well as a decrease in the amount of I were observed in the interfacial region. From the analysis, these states and not the heating of the perovskite were concluded to be the cause of the barrier. This strongly suggests that the detrimental effects can be avoided by controlling the interfacial design.

  • 40.
    Hultqvist, Adam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solar Cell Technology.
    Jacobsson, T. Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Helmholtz Ctr Berlin, Div Renewable Energies, D-14109 Berlin, Germany.
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solar Cell Technology.
    Cappel, Ute B.
    KTH Royal Inst Technol, Dept Chem, S-11428 Stockholm, Sweden.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solar Cell Technology.
    SnOx Atomic Layer Deposition on Bare Perovskite: An Investigation of Initial Growth Dynamics, Interface Chemistry, and Solar Cell Performance2021In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 4, no 1, p. 510-522Article in journal (Refereed)
    Abstract [en]

    High-end organic–inorganic lead halide perovskite semitransparent p–i–n solar cells for tandem applications use a phenyl-C61-butyric acid methyl ester (PCBM)/atomic layer deposition (ALD)-SnOx electron transport layer stack. Omitting the PCBM would be preferred for manufacturing, but has in previous studies on (FA,MA)Pb(Br,I)3 and (Cs,FA)Pb(Br,I)3 and in this study on Cs0.05FA0.79MA0.16PbBr0.51I2.49 (perovskite) led to poor solar cell performance because of a bias-dependent light-generated current. A direct ALD-SnOx exposure was therefore suggested to form a nonideal perovskite/SnOx interface that acts as a transport barrier for the light-generated current. To further investigate the interface formation during the initial ALD SnOx growth on the perovskite, the mass dynamics of monitor crystals coated by partial p–i–n solar cell stacks were recorded in situ prior to and during the ALD using a quartz crystal microbalance. Two major finds were made. A mass loss was observed prior to ALD for growth temperatures above 60 °C, suggesting the decomposition of the perovskite. In addition, a mostly irreversible mass gain was observed during the first exposure to the Sn precursor tetrakis(dimethylamino)tin(IV) that is independent of growth temperature and that disrupts the mass gain of the following 20–50 ALD cycles. The chemical environments of the buried interface were analyzed by soft and hard X-ray photoelectron spectroscopy for a sample with 50 ALD cycles of SnOx on the perovskite. Although measurements on the perovskite bulk below and the SnOx film above did not show chemical changes, additional chemical states for Pb, Br, and N as well as a decrease in the amount of I were observed in the interfacial region. From the analysis, these states and not the heating of the perovskite were concluded to be the cause of the barrier. This strongly suggests that the detrimental effects can be avoided by controlling the interfacial design.

    Download full text (pdf)
    FULLTEXT01
  • 41.
    Jacobsson, Jesper
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Andrei, Virgil
    Univ Cambridge, Dept Chem, Lensfield Rd, Cambridge CB2 1EW, England.
    Rivett, Jasmine P. H.
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England.
    Kornienko, Nikolay
    Univ Cambridge, Dept Chem, Lensfield Rd, Cambridge CB2 1EW, England.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute B.
    KTH Royal Inst Technol, Dept Chem, Tekn Ringen 30, S-10044 Stockholm, Sweden.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Deschler, Felix
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Extending the Compositional Space of Mixed Lead Halide Perovskites by Cs, Rb, K, and Na Doping2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 25, p. 13548-13557Article in journal (Refereed)
    Abstract [en]

    A trend in high performing lead halide perovskite solar cell devices has been increasing compositional complexity by successively introducing more elements, dopants, and additives into the structure; and some of the latest top efficiencies have been achieved with a quadruple cation mixed halide perovskite Cs(x)FA(y)MA(z)Rb(1-x-y-z)PbBr(q)I(3-9). This paper continues this trend by exploring doping of mixed lead halide perovskites, FA(0.83)MA(0.17)PbBr(0.51)I(2.49), with an extended set of alkali cations, i.e., Cs+, Rb+, K+, and Na+, as well as combinations of them. The doped perovskites were investigated with X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, hard X-ray photoelectron spectroscopy, UV-vis, steady state fluorescence, and ultrafast transient absorption spectroscopy. Solar cell devices were made as well. Cs+ can replace the organic cations in the perovskite structure, but Rb+, K+, and Na+ do not appear to do that. Despite this, samples doped with K and Na have substantially longer fluorescence lifetimes, which potentially could be beneficial for device performance.

  • 42.
    Jacobsson, T. Jesper
    et al.
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, S-75120 Uppsala, Sweden.;Helmholtz Zentrum Berlin Mat & Energie GmbH, Young Investigator Grp Hybrid Mat Format & Scalin, Albert Einstein Str 16, D-12489 Berlin, Germany..
    Hultqvist, Adam
    Uppsala Univ, Dept Engn Sci, Solid State Elect Div, Box 534, S-75121 Uppsala, Sweden..
    Svanström, Sebastian
    Uppsala Univ, Dept Phys & Astron, Box 5516, S-75120 Uppsala, Sweden..
    Riekehr, Lars
    Uppsala Univ, Dept Engn Sci, Solid State Elect Div, Box 534, S-75121 Uppsala, Sweden..
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Unger, Eva
    Helmholtz Zentrum Berlin Mat & Energie GmbH, Young Investigator Grp Hybrid Mat Format & Scalin, Albert Einstein Str 16, D-12489 Berlin, Germany.;Lund Univ, Chem Phys & NanoLund, POB 124, S-22100 Lund, Sweden..
    Rensmo, Håkan
    Uppsala Univ, Dept Phys & Astron, Box 5516, S-75120 Uppsala, Sweden..
    Johansson, Erik M. J.
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, S-75120 Uppsala, Sweden..
    Edoff, Marika
    Uppsala Univ, Dept Engn Sci, Solid State Elect Div, Box 534, S-75121 Uppsala, Sweden..
    Boschloo, Gerrit
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, S-75120 Uppsala, Sweden..
    2-Terminal CIGS-perovskite tandem cells: A layer by layer exploration2020In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 207, p. 270-288Article in journal (Refereed)
    Abstract [en]

    This paper focuses on the development of 2-terminal CIGS-perovskite tandem solar cells by exploring a range of stack sequences and synthetic procedures for depositing the associated layers. In the end, we converged at a stack sequence composed of SLG/Mo/CIGS/CdS/i-ZnO/ZnO:Al/NiO/PTAA/Perovskite/LiF/PCBM/SnO2/ITO. With this architecture, we reached performances only about 1% lower than the corresponding 4-terminal tandem cells, thus demonstrating functional interconnects between the two sub-cells while grown monolithically on top of each other. We go through the stack, layer-by-layer, discussing their deposition and the results, from which we can conclude what works, what does not work, and what potentially could work after additional modifications. The challenges for a successful 2-terminal tandem device include: how to deal with, or decrease, the surface roughness of the CIGS-stack, how to obtain uniform coverage of the layers between the CIGS and the perovskite while also obtaining a benign interface chemistry, and how to tune the band gaps of both the CIGS and the perovskite to obtain good optical matching. The investigation was based on CIGS with a power conversion efficiency around 14%, and perovskites with an efficiency around 12%, resulting in 2-terminal tandem cells with efficiencies of 15-16%. The results indicate that by using higher performing CIGS and perovskite sub-cells, it should be possible to manufacture highly efficient 2-terminal CIGS-perovskite tandem devices by using the protocols, principles, and procedures developed and discussed in this paper.

  • 43.
    Jacobsson, T. Jesper
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Helmholtz Zentrum Berlin Mat & Energie GmbH, Young Investigator Grp Hybrid Mat Format & Scalin, Albert Einstein Str 16, D-12489 Berlin, Germany.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Solid-State Electronics.
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Riekehr, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Solid-State Electronics.
    Cappel, Ute B.
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden.
    Unger, Eva
    Helmholtz Zentrum Berlin Mat & Energie GmbH, Young Investigator Grp Hybrid Mat Format & Scalin, Albert Einstein Str 16, D-12489 Berlin, Germany; Lund Univ, Chem Phys & NanoLund, POB 124, S-22100 Lund, Sweden.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Solid-State Electronics.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    2-Terminal CIGS-perovskite tandem cells: A layer by layer exploration2020In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 207, p. 270-288Article in journal (Refereed)
    Abstract [en]

    This paper focuses on the development of 2-terminal CIGS-perovskite tandem solar cells by exploring a range of stack sequences and synthetic procedures for depositing the associated layers. In the end, we converged at a stack sequence composed of SLG/Mo/CIGS/CdS/i-ZnO/ZnO:Al/NiO/PTAA/Perovskite/LiF/PCBM/SnO2/ITO. With this architecture, we reached performances only about 1% lower than the corresponding 4-terminal tandem cells, thus demonstrating functional interconnects between the two sub-cells while grown monolithically on top of each other. We go through the stack, layer-by-layer, discussing their deposition and the results, from which we can conclude what works, what does not work, and what potentially could work after additional modifications. The challenges for a successful 2-terminal tandem device include: how to deal with, or decrease, the surface roughness of the CIGS-stack, how to obtain uniform coverage of the layers between the CIGS and the perovskite while also obtaining a benign interface chemistry, and how to tune the band gaps of both the CIGS and the perovskite to obtain good optical matching. The investigation was based on CIGS with a power conversion efficiency around 14%, and perovskites with an efficiency around 12%, resulting in 2-terminal tandem cells with efficiencies of 15–16%. The results indicate that by using higher performing CIGS and perovskite sub-cells, it should be possible to manufacture highly efficient 2-terminal CIGS-perovskite tandem devices by using the protocols, principles, and procedures developed and discussed in this paper.

    Download full text (pdf)
    fulltext
  • 44.
    Jacobsson, T. Jesper
    et al.
    Uppsala Univ, Dept Chem, Box 538, S-75121 Uppsala, Sweden..
    Svanström, Sebastian
    Uppsala Univ, Dept Phys & Astron, Box 5516, S-75120 Uppsala, Sweden..
    Andrei, Virgil
    Univ Cambridge, Dept Chem, Lensfield Rd, Cambridge CB2 1EW, England..
    Rivett, Jasmine P. H.
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Kornienko, Nikolay
    Univ Cambridge, Dept Chem, Lensfield Rd, Cambridge CB2 1EW, England..
    Philippe, Bertrand
    Uppsala Univ, Dept Phys & Astron, Box 5516, S-75120 Uppsala, Sweden..
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Rensmo, Håkan
    Uppsala Univ, Dept Phys & Astron, Box 5516, S-75120 Uppsala, Sweden..
    Deschler, Felix
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Boschloo, Gerrit
    Uppsala Univ, Dept Chem, Box 538, S-75121 Uppsala, Sweden..
    Extending the Compositional Space of Mixed Lead Halide Perovskites by Cs, Rb, K, and Na Doping2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 25, p. 13548-13557Article in journal (Refereed)
    Abstract [en]

    A trend in high performing lead halide perovskite solar cell devices has been increasing compositional complexity by successively introducing more elements, dopants, and additives into the structure; and some of the latest top efficiencies have been achieved with a quadruple cation mixed halide perovskite Cs(x)FA(y)MA(z)Rb(1-x-y-z)PbBr(q)I(3-9). This paper continues this trend by exploring doping of mixed lead halide perovskites, FA(0.83)MA(0.17)PbBr(0.51)I(2.49), with an extended set of alkali cations, i.e., Cs+, Rb+, K+, and Na+, as well as combinations of them. The doped perovskites were investigated with X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, hard X-ray photoelectron spectroscopy, UV-vis, steady state fluorescence, and ultrafast transient absorption spectroscopy. Solar cell devices were made as well. Cs+ can replace the organic cations in the perovskite structure, but Rb+, K+, and Na+ do not appear to do that. Despite this, samples doped with K and Na have substantially longer fluorescence lifetimes, which potentially could be beneficial for device performance.

  • 45. Johansson, F. O. L.
    et al.
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Fondell, M.
    Han, Y.
    Gorgoi, M.
    Leifer, K.
    Lindblad, A.
    Tailoring ultra-fast charge transfer in MoS22020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 18, p. 10335-10342Article in journal (Refereed)
    Abstract [en]

    Charge transfer dynamics are of importance in functional materials used in devices ranging from transistors to photovoltaics. The understanding of charge transfer in particular of how fast electrons tunnel away from an excited state and where they end up, is necessary to tailor materials used in devices. We have investigated charge transfer dynamics in different forms of the layered two-dimensional material molybdenum disulphide (MoS2, in single crystal, nanocrystalline particles and crystallites in a reduced graphene oxide network) using core-hole clock spectroscopy. By recording the electrons in the sulphur KLL Auger electron kinetic energy range we have measured the prevalence of localised and delocalised decays from a state created by core excitation using X-rays. We show that breaking the crystal symmetry of the single crystal into either particles or sheets causes the charge transfer from the excited state to occur faster, even more so when incorporating it in a graphene oxide network. The interface between the MoS2 and the reduced graphene oxide forms a Schottky barrier which changes the ratio between local and delocalised decays creating two distinct regions in the charge transfer dependent on the energy of the excited electron. Thereby we show that ultra-fast charge transfer in MoS2 can be tailored, a result which can be used in the design of emergent devices.

  • 46.
    Johansson, F. O. L.
    et al.
    Uppsala Univ, Dept Phys & Astron, Mol & Condensed Matter Phys, Box 516, SE-75120 Uppsala, Sweden..
    Ivanovic, M.
    Univ Tubingen, Inst Phys & Theoret Chem, Morgenstelle 18, D-72076 Tubingen, Germany..
    Svanstrom, S.
    Uppsala Univ, Dept Phys & Astron, Mol & Condensed Matter Phys, Box 516, SE-75120 Uppsala, Sweden..
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. Uppsala Univ, Dept Phys & Astron, Mol & Condensed Matter Phys, Box 516, SE-75120 Uppsala, Sweden.
    Peisert, H.
    Univ Tubingen, Inst Phys & Theoret Chem, Morgenstelle 18, D-72076 Tubingen, Germany..
    Chasse, T.
    Univ Tubingen, Inst Phys & Theoret Chem, Morgenstelle 18, D-72076 Tubingen, Germany..
    Lindblad, A.
    Uppsala Univ, Dept Phys & Astron, Mol & Condensed Matter Phys, Box 516, SE-75120 Uppsala, Sweden..
    Femtosecond and Attosecond Electron-Transfer Dynamics in PCPDTBT:PCBM Bulk Heterojunctions2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 24, p. 12605-12614Article in journal (Refereed)
    Abstract [en]

    Charge separation efficiency is a crucial parameter for photovoltaic devices-polymers consisting of alternating electron-rich and electron-deficient parts can achieve high such efficiencies, for instance, together with a fullerene electron acceptor. This offers a viable path toward solar cells with organic bulk heterojunctions. Here, we measured the charge-transfer times in the femtosecond and attosecond regimes via the decay of sulfur is X-ray core excited states (with the core-hole clock method) in blends of a low-band gap polymer {PCPDTBT [poly[2,6-(4,4-bis (2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-1/1 dithiophene)-alt-4,7- (2,1,3-benzothiadiazole)]]} consisting of a cyclopentadithiophene electron-rich part and a benzothiadiazole electron-deficient part. The constituting parts of the bulk heterojunction were varied by adding the fullerene derivative PCBM ([6,6]-phenyl-C-61-butyric acid methyl ester) (weight ratio of polymer/PCBM as 1:0, 1:1, 1:2, and 1:3). For low-energy excitations, the charge-transfer time varies to the largest extent for the thiophene donor part. The charge-transfer time in the 1:2 blend is reduced by 86% compared to that of pristine PCPDTBT. At higher energy excitations, the charge-transfer time does not vary with the chemical environment, as this regime is dominated by intramolecular conduction that yields ultrafast charge-transfer times for all blends, approaching 170 as. We thus demonstrate that the core-hole clock method applied to a series with changing composition can give information about local electron dynamics (with chemical specificity) at interfaces between the constituting parts the crucial part of a bulk heterojunction where the initial charge separation occurs.

  • 47.
    Johansson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute B.
    Fondell, Mattis
    Han, Yuanyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Gorgoi, Mihaela
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Tailoring Ultra-fast Charge Transfer in MoS22020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 18, p. 10335-10342Article in journal (Refereed)
    Abstract [en]

    Charge transfer dynamics are of importance in functional materials used in devices ranging from transistors to photovoltaics. The understanding of charge transfer in particular of how fast electrons tunnel away from an excited state and where they end up, is necessary to tailor materials used in devices. We have investigated charge transfer dynamics in different forms of the layered two-dimensional material molybdenum disulphide (MoS2, in single crystal, nanocrystalline particles and crystallites in a reduced graphene oxide network) using core-hole clock spectroscopy. By recording the electrons in the sulphur KLL Auger electron kinetic energy range we have measured the prevalence of localised and delocalised decays from a state created by core excitation using X-rays. We show that breaking the crystal symmetry of the single crystal into either particles or sheets causes the charge transfer from the excited state to occur faster, even more so when incorporating it in a graphene oxide network. The interface between the MoS2 and the reduced graphene oxide forms a Schottky barrier which changes the ratio between local and delocalised decays creating two distinct regions in the charge transfer dependent on the energy of the excited electron. Thereby we show that ultra-fast charge transfer in MoS2 can be tailored, a result which can be used in the design of emergent devices.

    Download full text (pdf)
    fulltext
  • 48.
    Johansson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ivanovic, M.
    Univ Tubingen, Inst Phys & Theoret Chem, Morgenstelle 18, D-72076 Tubingen, Germany..
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, Stockholm, Sweden..
    Peisert, H.
    Univ Tubingen, Inst Phys & Theoret Chem, Morgenstelle 18, D-72076 Tubingen, Germany..
    Chasse, T.
    Univ Tubingen, Inst Phys & Theoret Chem, Morgenstelle 18, D-72076 Tubingen, Germany..
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Femtosecond and Attosecond Electron-Transfer Dynamics in PCPDTBT: PCBM Bulk Heterojunctions2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 24, p. 12605-12614Article in journal (Refereed)
    Abstract [en]

    Charge separation efficiency is a crucial parameter for photovoltaic devices-polymers consisting of alternating electron-rich and electron-deficient parts can achieve high such efficiencies, for instance, together with a fullerene electron acceptor. This offers a viable path toward solar cells with organic bulk heterojunctions. Here, we measured the charge-transfer times in the femtosecond and attosecond regimes via the decay of sulfur is X-ray core excited states (with the core-hole clock method) in blends of a low-band gap polymer {PCPDTBT [poly[2,6-(4,4-bis (2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-1/1 dithiophene)-alt-4,7- (2,1,3-benzothiadiazole)]]} consisting of a cyclopentadithiophene electron-rich part and a benzothiadiazole electron-deficient part. The constituting parts of the bulk heterojunction were varied by adding the fullerene derivative PCBM ([6,6]-phenyl-C-61-butyric acid methyl ester) (weight ratio of polymer/PCBM as 1:0, 1:1, 1:2, and 1:3). For low-energy excitations, the charge-transfer time varies to the largest extent for the thiophene donor part. The charge-transfer time in the 1:2 blend is reduced by 86% compared to that of pristine PCPDTBT. At higher energy excitations, the charge-transfer time does not vary with the chemical environment, as this regime is dominated by intramolecular conduction that yields ultrafast charge-transfer times for all blends, approaching 170 as. We thus demonstrate that the core-hole clock method applied to a series with changing composition can give information about local electron dynamics (with chemical specificity) at interfaces between the constituting parts the crucial part of a bulk heterojunction where the initial charge separation occurs.

    Download full text (pdf)
    fulltext
  • 49.
    Kammlander, Birgit
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Svanström, S.
    Kühn, D.
    Johansson, F. O. L.
    Sinha, S.
    Rensmo, H.
    Garcia Fernandez, Alberto
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Cappel, Ute B.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Thermal degradation of lead halide perovskite surfaces2022In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 58, no 97, p. 13523-13526Article in journal (Refereed)
    Abstract [en]

    Commercial use of lead halide perovskites requires improved thermal stability and therefore a better understanding of their degradation mechanisms. The thermal degradation of three clean perovskite single crystal surfaces (MAPbI3, MAPbBr3, FAPbBr3) was investigated using synchrotron-based photoelectron spectroscopy. Central findings are that the halide has a large impact on thermal stability and that the degradation of formamidnium results in the formation of a new organic species at the FAPbBr3 crystal surface. 

  • 50.
    Kammlander, Birgit
    et al.
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Kuehn, Danilo
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Johansson, Fredrik O. L.
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden.;Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.;Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany.;Sorbonne Univ, CNRS, Inst NanoSci Paris, INSP, F-75005 Paris, France..
    Sinha, Swarnshikha
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.;Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Garcia-Fernandez, Alberto
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Cappel, Ute B.
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Thermal degradation of lead halide perovskite surfaces2022In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 58, no 97, p. 13523-13526Article in journal (Refereed)
    Abstract [en]

    Commercial use of lead halide perovskites requires improved thermal stability and therefore a better understanding of their degradation mechanisms. The thermal degradation of three clean perovskite single crystal surfaces (MAPbI(3), MAPbBr(3), FAPbBr(3)) was investigated using synchrotron-based photoelectron spectroscopy. Central findings are that the halide has a large impact on thermal stability and that the degradation of formamidnium results in the formation of a new organic species at the FAPbBr(3) crystal surface.

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