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Electric field induced optical anisotropy of P3HT nanofibers in a liquid solution
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.ORCID iD: 0000-0002-3368-9786
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2015 (English)In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 5, no 11, 2642-2647 p.Article in journal (Refereed) PublishedText
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.

Place, publisher, year, edition, pages
Optical Society of America, 2015. Vol. 5, no 11, 2642-2647 p.
Keyword [en]
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
National Category
Materials Engineering
URN: urn:nbn:se:kth:diva-181212DOI: 10.1364/OME.5.002642ISI: 000364467700027ScopusID: 2-s2.0-84947753945OAI: diva2:902283

QC 20160210

Available from: 2016-02-10 Created: 2016-01-29 Last updated: 2016-05-19Bibliographically approved
In thesis
1. Semiconducting Polymer Nanofibers and Quantum Dot based Nanocomposites for Optoelectronic Applications
Open this publication in new window or tab >>Semiconducting Polymer Nanofibers and Quantum Dot based Nanocomposites for Optoelectronic Applications
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanostructured materials have attracted a broad interest in various technologies such as optoelectronics. In this thesis, nanostructured semiconductor nanocrystals, including inorganic and organic materials, were fabricated by solution based methods. The reaction conditions were optimized to control the size and morphology of the obtained nanocrystals. The optical and photoelectric properties of nanocrystals were evaluated for potential optoelectronic applications.

Colloidal CdSe quantum dots (QDs) were synthesized via thermolysis method and layers of CdS was further grown on the core CdSe QDs to form a core-shell heterostructure quantum dots (HQDs). The optical properties of HQDs were evaluated and showed the characteristics of quasi-type-II alignment of energy levels, which has potential for excitonic solar cell (XSC) application.

Nanofibers of the semiconducting polymer poly-(3-hexylthiophene) (P3HT) were synthesized via a modified whisker method. In order to control the size (both the length and the diameter) of nanofibers, we systematically studied the ratio between mixture solvents and the solute concentration. In addition, the degradation processes of P3HT nanofibers on different substrates under various environments were investigated. We found that the degradation of P3HT nanofibers can be effectively suppressed by using the substrate of higher conductivity. A nanocomposite consisting of HQDs and P3HT nanofibers was fabricated and its photoelectric properties were evaluated by I-V measurements. A ‘turn-on’ voltage was found and revealed the localization of excited holes within the HQDs, which confirmed the quasi-type-II alignment between core and shell energy levels.

In addition, we aligned the P3HT nanofibers by applying the external electric field. Alternating current (AC) and direct current (DC) induced alignments of P3HT nanofibers were investigated respectively to study the effects of different electric fields on the alignment behavior. It was determined that the AC electric field allowed a better alignment of nanofibers. Moreover, two different lengths of P3HT nanofibers were aligned and their absorption spectra were measured. Under polarized light beams, we observed a better aligned pattern in the case of longer nanofibers, shown as a higher dichroic ratio calculated from optical absorption spectra. These aligned nanofibers may find applications in optoelectronic devices.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 57 p.
National Category
Nano Technology
Research subject
urn:nbn:se:kth:diva-187255 (URN)978-91-7595-946-7 (ISBN)
Public defence
2016-06-15, Sal C, Electrum, Isafjordsgatan 26, Stockholm, 10:00 (English)

QC 20160519

Available from: 2016-05-19 Created: 2016-05-18 Last updated: 2016-05-20Bibliographically approved

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