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Influence of morphological disorder on in- and out-of-plane charge transport in conjugated polymer films

Published online by Cambridge University Press:  20 November 2015

Anton Li
Affiliation:
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
Ban Xuan Dong
Affiliation:
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
Peter F. Green*
Affiliation:
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
*
*Address all correspondence to Peter F. Green atpfgreen@umich.edu
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Abstract

Thin films of the conjugated polymer poly(3-hexylthiophene) (P3HT) of different morphological structures were fabricated using both conventional spin-casting and the matrix-assisted pulsed laser evaporation (MAPLE). Films deposited by MAPLE exhibit inhomogeneous morphologies comprised globular subfeatures with dimensions of the order of 100 nm. We show that whereas the in-plane carrier mobilities of MAPLE-deposited films (8.3 × 10−3 cm2/V/s) are comparable with those of spin-cast analogs (5.5 × 10−3 cm2/V/s), the out-of-plane mobilities are an order of magnitude lower (4.1 × 10−4 cm2/V/s versus 2.7 × 10−3 cm2/V/s). Both in- and out-of-plane carrier transport characteristics of MAPLE-deposited films indicate a broad density of states and high carrier trap concentration. Optical absorbance spectroscopy not only corroborates a high degree of energetic disorder in MAPLE-deposited films, but also suggests that the P3HT chains possess average conjugation lengths comparable with spin-cast counterparts. Our findings, rationalized in terms of the Gaussian Disorder Model, describing carrier transport in an environment characterized by both positional and energetic disorder, provide important perspectives on the extent to which disorder impacts mechanisms of charge transport in conjugated polymers.

Type
Research Letters
Copyright
Copyright © Materials Research Society 2015 

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