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Lead-free Metal Halide based Solar Cells
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. (Erik Johansson)
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lead-halide perovskites have recently appeared as very promising materials for solar cells. However, their stability and toxicity may be limiting factors for their application. Therefore, to find new low toxic and high stability light harvesters may be necessary for overcoming the challenges of perovskite solar cells. The overall aim of this thesis is to explore new low toxic light harvesters and to investigate their possibility for application of solar cells. The focus in the thesis is on bismuth halide-based light harvesters, which show high light absorption coefficient and promising photovoltaic performance. Specifically, the investigated materials are different compositions of metal halides in which silver, Ag or cesium, Cs, are combined with bismuth, Bi, or antimony, Sb and the halides iodide, I, or bromide, Br. All of the systems show very promising optical performances, however, their photovoltaic performances are still low, which is partially due to the recombination and defects issues, etc. Through adjusting the elemental compositions by mixing Bi/Sb or I/Br the optical properties were tuned. By varying fabrication conditions or devices architectures, the results in this thesis also show that all the low toxic light harvesters works in solar cells, which possibly can be utilized in future photovoltaics.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. , p. 79
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1840
Keywords [en]
Low-toxicity, emerging light harvesters, lead-free, low toxic bismuth, Ag (Cs)-Bi (Sb)-I (Br) systems, 2D perovskites.
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-391058ISBN: 978-91-513-0722-0 (print)OAI: oai:DiVA.org:uu-391058DiVA, id: diva2:1343606
Public defence
2019-10-04, Polhemsalen, Ångstrom 10134, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2019-09-12 Created: 2019-08-18 Last updated: 2019-10-15Bibliographically approved
List of papers
1. Extended Photo-Conversion Spectrum in Low-Toxic Bismuth Halide Perovskite Solar Cells
Open this publication in new window or tab >>Extended Photo-Conversion Spectrum in Low-Toxic Bismuth Halide Perovskite Solar Cells
2016 (English)In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 17, p. 3467-3471Article in journal (Refereed) Published
Abstract [en]

Lead-based perovskites show very promising properties for use in solar cells; however, the toxicity of lead is a potential inhibitor for large-scale application of these solar cells. Here, a low-toxic bismuth halide, CsBi3I10, is synthesized from solution and the optical properties and crystal structure are compared with previously reported Cs3Bi2I9 perovskite, and the photovoltaic properties are also investigated. The XRD pattern suggests that the CsBi3I10 film has a layered structure with a different dominating crystal growth direction than the Cs3Bi2I9 perovskite. A band gap of 1.77 eV is obtained for the CsBi3I10 film, which is smaller than the band gap of Cs3Bi2I9 at 2.03 eV, and an extended visible light absorption spectrum is therefore obtained. The solar cell device with CsBi3I10 shows a photocurrent up to 700 nm, and this work shows therefore the possibility for increased light absorption and higher photocurrents in solar cells based on bismuth halide perovskites.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-307858 (URN)10.1021/acs.jpclett.6b01452 (DOI)000382603300029 ()27538852 (PubMedID)
Funder
Swedish Energy AgencySwedish Research CouncilSwedish Research Council FormasÅForsk (Ångpanneföreningen's Foundation for Research and Development)Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of Technology
Available from: 2016-11-23 Created: 2016-11-22 Last updated: 2019-09-04Bibliographically approved
2. The Effect of Dopant-Free Hole-Transport Polymers on Charge Generation and Recombination in Cesium-Bismuth-Iodide Solar Cells
Open this publication in new window or tab >>The Effect of Dopant-Free Hole-Transport Polymers on Charge Generation and Recombination in Cesium-Bismuth-Iodide Solar Cells
2018 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 11, no 6, p. 1114-1120Article in journal (Refereed) Published
Abstract [en]

The photovoltaic characteristics of CsBi3I10-based solar cells with three dopant-free hole-conducting polymers are investigated. The effect on charge generation and charge recombination in the solar cells using the different polymers is studied and the results indicate that the choice of polymer strongly affects the device properties. Interestingly, for the solar cell with poly[[2,3-bis(3-octyloxyphenyl)-5,8-quinoxalinediyl]-2,5-thiophenediyl] (TQ1), the photon-to-current conversion spectrum is highly improved in the red wavelength region, suggesting that the polymer also contributes to the photocurrent generation in this case. This report provides a new direction for further optimization of Bi-halide solar cells by using dopant-free hole-transporting polymers and shows that the energy levels and the interaction between the Bi-halide and the conducting polymers are very important for solar cell performance.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2018
Keywords
bismuth, cesium bismuth iodide, htm, polymer, solar cells
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-354358 (URN)10.1002/cssc.201702169 (DOI)000428315300015 ()29372625 (PubMedID)
Funder
Swedish Energy AgencySwedish Research CouncilSwedish Research Council Formas
Available from: 2018-06-28 Created: 2018-06-28 Last updated: 2019-09-04Bibliographically approved
3. High Photon-to-Current Conversion in Solar Cells Based on Light-Absorbing Silver Bismuth Iodide
Open this publication in new window or tab >>High Photon-to-Current Conversion in Solar Cells Based on Light-Absorbing Silver Bismuth Iodide
2017 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 12, p. 2592-2596Article in journal (Refereed) Published
Abstract [en]

Here, a lead-free silver bismuth iodide (AgI/BiI3) with a crystal structure with space group R (3) over barm is investigated for use in solar cells. Devices based on the silver bismuth iodide deposited from solution on top of TiO2 and the conducting polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) as a hole-transport layer are prepared and the photovoltaic performance is very promising with a power conversion efficiency over 2%, which is higher than the performance of previously reported bismuth-halide materials for solar cells. Photocurrent generation is observed between 350 and 700 nm, and the maximum external quantum efficiency is around 45%. The results are compared to solar cells based on the previously reported material AgBi2I7, and we observe a clearly higher performance for the devices with the new silver and bismuth iodides composition and different crystal structure. The X-ray diffraction spectrum of the most efficient silver bismuth iodide material shows a hexagonal crystal structure with space group R (3) over barm, and from the light absorption spectrum we obtain an indirect band gap energy of 1.62 eV and a direct band gap energy of 1.85 eV. This report shows the possibility for finding new structures of metal-halides efficient in solar cells and points out new directions for further exploration of lead-free metal-halide solar cells.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2017
Keywords
perovskite solar cells, power conversion efficiency, silver bismuth iodide, space group, x-ray diffraction
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-329649 (URN)10.1002/cssc.201700634 (DOI)000403934400007 ()28481063 (PubMedID)
Funder
Swedish Energy AgencySwedish Research CouncilSwedish Research Council FormasGöran Gustafsson Foundation for Research in Natural Sciences and Medicine
Available from: 2017-09-26 Created: 2017-09-26 Last updated: 2019-09-04Bibliographically approved
4. Silver-Bismuth-Antimony-Iodide Materials for Solar Cell Application
Open this publication in new window or tab >>Silver-Bismuth-Antimony-Iodide Materials for Solar Cell Application
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-391057 (URN)
Available from: 2019-08-18 Created: 2019-08-18 Last updated: 2019-09-04
5. Bandgap Tuning of Silver Bismuth Iodide via Controllable Bromide Substitution for Improved Photovoltaic Performance
Open this publication in new window or tab >>Bandgap Tuning of Silver Bismuth Iodide via Controllable Bromide Substitution for Improved Photovoltaic Performance
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2019 (English)In: ACS APPLIED ENERGY MATERIALSArticle in journal (Refereed) Accepted
Abstract [en]

In this work, silver-bismuth-halide thin films, exhibiting low toxicity and good stability, were explored systemically by gradually substituting iodide, I, with bromide, Br, in the AgBi2I7 system. It was found that the optical bandgap can be tuned by varying the I/Br ratio. Moreover, the film quality was improved when introducing a small amount of Br. The solar cell was demonstrated to be more stable at ambient conditions and most efficient when incorporating 10% Br, as a result of decreased recombination originating from the increased grain size. Thus, replacing a small amount of I with Br was beneficial for photovoltaic performance.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
lead-free solar cells, power conversion efficiency, bandgap, silver bismuth iodide, mixed-halide composition, grain size, density functional theory
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-391056 (URN)10.1021/acsaem.9b00914 (DOI)000483434700003 ()
Funder
Swedish Research CouncilSwedish Energy Agency
Available from: 2019-08-18 Created: 2019-08-18 Last updated: 2019-10-09Bibliographically approved
6. Bismuth Iodide Perovskite Materials for Solar Cell Applications: Electronic Structure, Optical Transitions and Directional Charge Transport
Open this publication in new window or tab >>Bismuth Iodide Perovskite Materials for Solar Cell Applications: Electronic Structure, Optical Transitions and Directional Charge Transport
Show others...
2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, p. 29039-29046Article in journal (Refereed) Published
Abstract [en]

Cesium and methylammonium bismuth iodides (Cs3Bi2I9 and MA(3)Bi(2)I(9)) are new low-toxic and air stable compounds in the perovskite solar cell family with promising characteristics. Here, the electronic structure and the nature of their optical transitions, dielectric constant, and charge carrier properties are assessed for photovoltaic applications with density functional theory (DFT) calculations and experiments. The calculated direct and indirect band gap values for Cs3Bi2I9 (2.17 and 2.0 eV) and MA(3)Bi(2)I(9) (2.17 and 1.97 eV) are found to be in good agreement with the experimental optical band gaps (2.2, 2.0 eV and 2.4, 2.1 eV for Cs3Bi2I9 and MA(3)Bi(2)I(9), respectively) estimated for solution-processed films. There is an error cancelation in the DFT calculated band gap similar to that for lead perovskites. However, fully relativistic DFT calculations indicate that the size of the spin orbit coupling (SOC) error cancelation for bismuth perovskite (0.5 eV) is less than for lead perovskite (1 eV), and other factors are therefore also important. Band structure calculations show high effective masses of the charge carriers along the c-axis but on the other hand lower electron effective mass in the a-b planes, revealing the interesting possibility for a directional charge transport. Calculations of dielectric constants, absorption coefficients, carrier effective masses, and exciton binding energies emphasize the fundamental differences between the lead and bismuth iodide perovskites and clarify the reasons behind the lower power conversion efficiency of bismuth iodide perovskite solar cells. Also the calculations show that the orientational disorder of the MA dipoles in the lattice has meaningful impacts on the near valence and conduction band edge of the electronic structure.

National Category
Physical Chemistry Engineering and Technology
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-311576 (URN)10.1021/acs.jpcc.6b11745 (DOI)000391160400016 ()
Funder
Swedish Energy AgencySwedish Research CouncilSwedish Research Council FormasSwedish National Infrastructure for Computing (SNIC), snic2015-6-65 snic2015-1-281
Available from: 2016-12-29 Created: 2016-12-29 Last updated: 2019-09-04Bibliographically approved

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