Macroscopic alignment of poly(3‐hexylthiophene) for enhanced long‐range collection of photogenerated carriers. Issue 2 (16th September 2015)

• Record Type: Journal Article
• Authors: Li, Anton; Bilby, David; Dong, Ban Xuan; Amonoo, Jojo; Kim, Jinsang; Green, Peter F.
• Is Part Of: Journal of polymer science. Volume 54:Issue 2(2016)
• Page Start: 180
• Page End: 188
• Publication Date: 2015-09-16
• Subjects: anisotropy -- charge transport -- conjugated polymers -- fibers -- morphology -- processing -- solar cells -- thin film transistors; 547
• DOI: 10.1002/polb.23888
• Languages: English
• ISSNs: 0887-6266

Abstract

ABSTRACT: An epitaxy‐directing solvent additive 1, 3, 5‐trichlorobenzene is combined with an off‐center spin‐casting technique to produce poly(3‐hexylthiophene) (P3HT) fibers with uniaxial in‐plane alignment on the centimeter scale. Photoconductive atomic force microscopy (pc‐AFM) is used to characterize planar heterojunction devices assembled from phenyl‐C61 butyric acid methyl ester (PCBM) acceptor and both aligned and unaligned P3HT donor. By varying the relative positions of the laser spot (site of carrier generation) and probe (site of hole extraction), it is found that devices with aligned P3HT exhibit anisotropic and greatly enhanced long‐range photocarrier transport, with nearly 10% of original photocurrent measured 400 µm from the laser spot along the direction parallel to the alignment. Complementary thin film transistor (TFT) measurements reveal a factor of ∼3.5 difference in the hole mobilities parallel and perpendicular to the direction of alignment. Together, these findings highlight the importance of macroscopic alignment as a strategy to overcome the low mobilities of disordered polymer semiconductors.1 © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 180–188 Abstract : Macroscopically‐aligned P3HT films are incorporated into bilayer solar cells, yielding a vast improvement in the long‐range migration and collection of photogenerated charges. The enhancement is correlated with anisotropic transport properties of the ordered polymer chains, motivating further development of large‐area directed alignment strategies to enable broader applicability of conjugated polymers for organic electronics.