Electric field induced optical anisotropy of P3HT nanofibers in a liquid solution

Lobov, Gleb; Zhao, Yichen; Marinins, Aleksandrs; Yan, Min; Li, Jiantong; Toprak, Muhammet S.; Sugunan, Abhilash; Thylén, Lars; Wosinski, Lech; Östling, Mikael; Popov, Sergei

doi:10.1364/ome.5.002642

Cited by 12 publications

(19 citation statements)

References 24 publications

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“…Because simple polarization measurements are not subject to theoretical upper and lower bounds, this renders comparisons between different experiments difficult. A good example of this difficulty is an attempt to compare our results with those of Lobov et al Although there are differences in the methods of sample preparation (we subject P3HT films to an electric field while they are drying; they place a P3HT nanofiber solution between two electrodes), nevertheless, we only use an electric field of 5.88 kV m −1 while they use a field of 600 kV m −1 . One would expect the higher field strength to yield a greater degree of orientation, but they report very small orientational effects.…”

Section: Resultsmentioning

confidence: 99%

“…Several optical methods have been used for studying the orientation of units in polymers, for example: polarized UV–vis absorption, polarized electroluminescence, and polarized emission . We note, however, that while these orientational measurements often are discussed in terms of the “anisotropy” of the sample, the anisotropy is not measured in the sense of Equation .…”

Section: Resultsmentioning

confidence: 99%

“…Here we investigate the use of steady‐state and time‐resolved fluorescence anisotropy along with polarized Raman spectroscopy to characterize the orientation of the polymer units. (Although several reports have appeared in the literature using polarization to investigate ordering of P3HT nanofibers, our study is the first to measure the anisotropy, a quantitative measure of orientation, as rigorously defined below in Equation .) Consistent with our anisotropy measurements, we observed an enhancement of in‐plane charge mobility in the films exposed to an electric field …”

Section: Introductionmentioning

confidence: 99%

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Characterizing Electric Field Exposed P3HT Thin Films Using Polarized‐Light Spectroscopies

Bhattacharjee

Elshobaki

Santra

et al. 2016

Macro Chemistry & Physics

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P3HT (poly (3‐hexylthiophene)) has been widely used as a donor in the active layer in organic photovoltaic devices. Although moderately high‐power conversion efficiencies have been achieved with P3HT‐based devices, structural details, such as the orientation of polymer units and the extent of H‐ and J‐aggregation are not yet fully understood; and different measures have been taken to control the ordering in the material. One such measure, which has been exploited, is to apply an electric field from a Van de Graaff generator. Fluorescence (to measure anisotropy instead of polarization, which is more commonly measured) and Raman spectroscopy are used to characterize the order of P3HT molecules in thin films resulting from the field. Preferential orientations of the units in a thin film are determined, consistent with observed hole mobility in thin‐film transistors, and it is observed that the apparent H‐coupling strength changes when the films are exposed to oriented electrical fields during drying.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Characterizing Electric Field Exposed P3HT Thin Films Using Polarized‐Light Spectroscopies

Bhattacharjee

Elshobaki

Santra

et al. 2016

Macro Chemistry & Physics

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“…More description about alignment methods such as rubbing, epitaxial solidification, spherulitic crystallization, and crystallization in microstructures can be found elsewhere . The AC poling method allows aligning P3HT nanofibers dispersed in nonconductive solvent by applying external AC electric field . When the solvent evaporates, aligned nanofibers precipitate on the substrate, maintaining their orientation and forming a layer of vertically ordered stack with 200–500 nm thickness.…”

Section: Introductionmentioning

confidence: 99%

“…When the solvent evaporates, aligned nanofibers precipitate on the substrate, maintaining their orientation and forming a layer of vertically ordered stack with 200–500 nm thickness. Static direct current (DC) electric field affects nanofibers similarly however most of the nanofibers become deposited on the negative electrode, which can be attributed to additional positive charge obtained as a result of oxidation reactions …”

Section: Introductionmentioning

confidence: 99%

Size Impact of Ordered P3HT Nanofibers on Optical Anisotropy

Lobov

Zhao

Marinins

et al. 2016

Macro Chemistry & Physics

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Poly-3-hexylthiophene (P3HT) nanofi bers are 1D crystalline structures with semiconductor properties. When P3HT nanofi bers are dispersed in nonconducting solvent, they react to external alternate electric fi eld by aligning along the fi eld 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 μm long nanofi bers exponentially increases with the magnitude of applied fi eld to a certain asymptotic limit at 0.8 V μm −1 , while 100-500 nm long nanofi bers respond to electric fi eld negligibly. Effective optical birefringence of oriented 2 μm 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.

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Dynamic Manipulation of Optical Anisotropy of Suspended Poly‐3‐hexylthiophene Nanofibers

Lobov

Zhao

Marinins

et al. 2016

Advanced Optical Materials

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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.

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Electric field induced optical anisotropy of P3HT nanofibers in a liquid solution

Cited by 12 publications

References 24 publications

Characterizing Electric Field Exposed P3HT Thin Films Using Polarized‐Light Spectroscopies

Characterizing Electric Field Exposed P3HT Thin Films Using Polarized‐Light Spectroscopies

Size Impact of Ordered P3HT Nanofibers on Optical Anisotropy

Dynamic Manipulation of Optical Anisotropy of Suspended Poly‐3‐hexylthiophene Nanofibers

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