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Electro-optical properties of one-dimensional organic crystals
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Optik och Fotonik, OFO.
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The recent development of photonics and applications puts new challenges for systems using emission, transmission and modulation of light. For these reasons, novel optical materials attract a special interest for their enabling properties for novel technologies.

In this work, we performed the research on fundamental properties and the possibility of implementation of electro-optical response of Poly-3-hexylthiophene-2,5-diyl (P3HT) nanofibers, which belong to the class of organic semiconductor crystalline materials. Our research demonstrated that an external electric field allows controlling the orientation of nanofibers dispersed in a solution by changing the electrical properties of P3HT crystals. This method was used to introduce a collective alignment of P3HT nanofibers and to impact the optical properties of the colloid. The spectroscopic and polarization measurements show that P3HT nanofibers possess optical anisotropy in a wide range of visible spectrum. This property combined with the ability to manipulate the orientation of nanofibers dynamically, was used for direct phase and intensity modulation of transmitted light. Along with these investigations, several engineering and technology tasks were solved. We have designed the transverse electro-optical cell using all-optical-fiber approach, as well as the longitudinal electro-optical cell was fabricated using a novel polymer molding technique.

The obtained research results demonstrate the potential of P3HT crystalline nanofibers as a material class of large niche of applications, not only limited to photovoltaics but also being implemented in electro-optical systems to control light polarization and propagation.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2017. , 55 s.
HSV kategori
Forskningsprogram
Fysik
Identifikatorer
URN: urn:nbn:se:kth:diva-220529OAI: oai:DiVA.org:kth-220529DiVA: diva2:1168953
Disputas
2017-11-24, Sal C, Electrum, Stockholm, 10:00 (engelsk)
Veileder
Merknad

QC 20171229

Tilgjengelig fra: 2017-12-29 Laget: 2017-12-22 Sist oppdatert: 2018-01-18bibliografisk kontrollert
Delarbeid
1. Electric field induced optical anisotropy of P3HT nanofibers in a liquid solution
Åpne denne publikasjonen i ny fane eller vindu >>Electric field induced optical anisotropy of P3HT nanofibers in a liquid solution
Vise andre…
2015 (engelsk)Inngår i: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 5, nr 11, 2642-2647 s.Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The nanofiber morphology of regioregular Poly-3- hexylthiophene (P3HT) is a 1D crystalline structure organized by π - π stacking of the backbone chains. In this study, we report the impact of electric field on the orientation and optical properties of P3HT nanofibers dispersed in liquid solution. We demonstrate that alternating electric field aligns nanofibers, whereas static electric field forces them to migrate towards the cathode. The alignment of nanofibers introduces anisotropic optical properties, which can be dynamically manipulated until the solvent has evaporated. Time resolved spectroscopic measurements revealed that the electro-optical response time decreases significantly with the magnitude of applied electric field. Thus, for electric field 1.3 V ·μm-1 the response time was measured as low as 20 ms, while for 0.65 V ·μm-1 it was 110-150 ms. Observed phenomenon is the first mention of P3HT supramolecules associated with electrooptical effect. Proposed method provides real time control over the orientation of nanofibers, which is a starting point for a novel practical implementation. With further development P3HT nanofibers can be used individually as an anisotropic solution or as an active component in a guest-host system.

sted, utgiver, år, opplag, sider
Optical Society of America, 2015
Emneord
Anisotropy, Electric fields, Nanofibers, Real time control, Alternating electric field, Anisotropic optical properties, Crystalline structure, Electric field induced, Electrooptical response, Poly-3-hexylthiophene, Spectroscopic measurements, Static electric fields, Optical properties
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-181212 (URN)10.1364/OME.5.002642 (DOI)000364467700027 ()2-s2.0-84947753945 (Scopus ID)
Merknad

QC 20160210

Tilgjengelig fra: 2016-02-10 Laget: 2016-01-29 Sist oppdatert: 2017-12-29bibliografisk kontrollert
2. Size Impact of Ordered P3HT Nanofibers on Optical Anisotropy
Åpne denne publikasjonen i ny fane eller vindu >>Size Impact of Ordered P3HT Nanofibers on Optical Anisotropy
Vise andre…
2016 (engelsk)Inngår i: Macromolecular Chemistry and Physics, ISSN 1022-1352, E-ISSN 1521-3935, Vol. 217, nr 9, 1089-1095 s.Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline structures with semiconductor properties. When P3HT nanofi bers are dispersed in nonconducting solvent, they react to external alternate electric field by aligning along the field lines. This can be used to create layers of ordered nanofi bers and is referred to as alternating current poling method. P3HT nanofi bers with three different size distributions are fabricated, using self-assembly mechanism in marginal solvents, and used for the alignment studies. Anisotropic absorption of oriented 2 mu m long nanofi bers exponentially increases with the magnitude of applied field to a certain asymptotic limit at 0.8 V mu m(-1), while 100-500 nm long nanofi bers respond to electric field negligibly. Effective optical birefringence of oriented 2 mu m long nanofi bers is calculated, based on the phase shift at 633 nm and the average layer thickness, to be 0.41. These results combined with further studies on real-time control over orientation of P3HT nanofi bers in liquid solution or host system are promising in terms of exploiting them in electroabsorptive and electrorefractive applications.

sted, utgiver, år, opplag, sider
John Wiley & Sons, 2016
Emneord
anisotropic optical materials, electro-optical materials, optical properties, polymers
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-188070 (URN)10.1002/macp.201500516 (DOI)000375688500008 ()2-s2.0-84964734770 (Scopus ID)
Merknad

QC 20160620

Tilgjengelig fra: 2016-06-20 Laget: 2016-06-03 Sist oppdatert: 2017-12-29bibliografisk kontrollert
3. Dynamic Manipulation of Optical Anisotropy of Suspended Poly-3-hexylthiophene Nanofibers
Åpne denne publikasjonen i ny fane eller vindu >>Dynamic Manipulation of Optical Anisotropy of Suspended Poly-3-hexylthiophene Nanofibers
Vise andre…
2016 (engelsk)Inngår i: Advanced Optical Materials, ISSN 2195-1071, Vol. 4, nr 10, 1651-1656 s.Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline semiconducting nanostructures, which are known for their application in photovoltaics. Due to the internal arrangement, P3HT nanofibers possess optical anisotropy, which can be enhanced on a macroscale if nanofibers are aligned. Alternating electric field, applied to a solution with dispersed nanofibers, causes their alignment and serves as a method to produce solid layers with ordered nanofibers. The transmission ellipsometry measurements demonstrate the dichroic absorption and birefringence of ordered nanofibers in a wide spectral range of 400–1700 nm. Moreover, the length of nanofibers has a crucial impact on their degree of alignment. Using electric birefringence technique, it is shown that external electric field applied to the solution with P3HT nanofibers can cause direct birefringence modulation. Dynamic alignment of dispersed nanofibers changes the refractive index of the solution and, therefore, the polarization of transmitted light. A reversible reorientation of nanofibers is organized by using a quadrupole configuration of poling electrodes. With further development, the described method can be used in the area of active optical fiber components, lab-on-chip or sensors. It also reveals the potential of 1D conducting polymeric structures as objects whose highly anisotropic properties can be implemented in electro-optical applications.​

sted, utgiver, år, opplag, sider
Wiley-VCH Verlagsgesellschaft, 2016
Emneord
anisotropic optical materials, electrooptical materials, nanofibers, optical properties, polymers, Anisotropy, Birefringence, Electric fields, Optical anisotropy, Optical fibers, Refractive index, Alternating electric field, Electric birefringence, Electro-optical applications, External electric field, Quadrupole configuration, Semiconducting nanostructures, Transmission ellipsometry
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-195418 (URN)10.1002/adom.201600226 (DOI)2-s2.0-84979574389 (Scopus ID)
Merknad

QC 20161128

Tilgjengelig fra: 2016-11-28 Laget: 2016-11-03 Sist oppdatert: 2017-12-29bibliografisk kontrollert
4. Electro-optical effects of high aspect ratio P3HT nanofibers colloid in polymer micro-fluid cells
Åpne denne publikasjonen i ny fane eller vindu >>Electro-optical effects of high aspect ratio P3HT nanofibers colloid in polymer micro-fluid cells
Vise andre…
2017 (engelsk)Inngår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, nr 11, 2157-2160 s.Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This Letter reports the electro-optical (EO) effect of Poly(3-hexylthiophene-2,5-diyl) (P3HT) nanofibers colloid in a polymer micro-fluidic EO cell. P3HT nanofibers are high aspect ratio semiconducting nanostructures, and can be collectively aligned by an external alternating electric field. Optical transmission modulated by the electric field is a manifestation of the electro-optical effect due to high inner crystallinity of P3HT nanofibers. According to our results, the degree of alignment reaches a maximum at 0.6 V/μm of electric field strength, implying a big polarizability value due to geometry and electrical properties of P3HT nanofibers. We believe that one-dimensional crystalline organic nanostructures have a large potential in EO devices due to their significant anisotropy, wide variety of properties, low actuation voltages, and opportunity to be tailored via adjustment of the fabrication process.

sted, utgiver, år, opplag, sider
OSA Publishing, 2017
Emneord
P3HT, Nanofibers, optofluidics, reaction injectin molding, RIM, OSTE, micro-fluid cells
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-207850 (URN)10.1364/OL.42.002157 (DOI)000403534700027 ()
Merknad

QC 20170613

Tilgjengelig fra: 2017-05-27 Laget: 2017-05-27 Sist oppdatert: 2017-12-29bibliografisk kontrollert
5. Direct birefringence and transmission modulation via dynamic alignment of P3HT nanofibers in an advanced opto-fluidic component
Åpne denne publikasjonen i ny fane eller vindu >>Direct birefringence and transmission modulation via dynamic alignment of P3HT nanofibers in an advanced opto-fluidic component
Vise andre…
2017 (engelsk)Inngår i: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 7, nr 1, 52-61 s.Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Poly-3-hexylthiophene (P3HT) nanofibers are semiconducting high-aspect ratio nanostructures with anisotropic absorption and birefringence properties found at different regions of the optical spectrum. In addition, P3HT nanofibers possess an ability to be aligned by an external electric field, while being dispersed in a liquid. In this manuscript we show that such collective ordering of nanofibers, similar to liquid crystal material, significantly changes the properties of transmitted light. With a specially fabricated opto-fluidic component, we monitored the phase and transmission modulation of light propagating through the solution of P3HT nanofibers, being placed in the electric field with strength up to 0.1 V/μm. This report describes a technique for light modulation, which can be implemented in optical fiber-based devices or on-chip integrated components.

Emneord
Absorption spectroscopy, Aspect ratio, Birefringence, Electric fields, Light modulation, Liquid crystals, Modulation, Nanofibers, Optical fiber fabrication, Optical fibers, Anisotropic absorption, Birefringence property, External electric field, Fiber-based device, High aspect ratio nano-structures, Liquid crystal materials, Poly-3-hexylthiophene, Transmission modulation, Light transmission
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-202242 (URN)10.1364/OME.7.000052 (DOI)000392205600007 ()2-s2.0-85008157720 (Scopus ID)
Merknad

Funding text: European Union (EU) project ICONE (Grant #608099); Swedish Research Council (VR-SRL 2012-4421, VR-SRL 2013-6780); Swedish Foundation for Strategic Research (SSF, Grant no EM11-0002). The authors acknowledge Prof. Walter Margulis for fruitful discussions regarding optical fiber components and for his assistance in improving the quality of the manuscript. QC 20170320

Tilgjengelig fra: 2017-03-20 Laget: 2017-03-20 Sist oppdatert: 2017-12-29bibliografisk kontrollert

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