Impact of molecular order on polaron formation in conjugated polymers

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Title: Impact of molecular order on polaron formation in conjugated polymers
Authors: Nightingale, J
Wade, J
Moia, D
Nelson, J
Kim, J-S
Item Type: Journal Article
Abstract: The nature of polaron formation has profound implications on the transport of charge carriers in conjugated polymers, but still remains poorly understood. Here we develop in situ electrochemical resonant Raman spectroscopy, a powerful structural probe that allows direct observation of polaron formation. We report that polaron formation in ordered poly(3-hexyl)thiophene (P3HT) polymer domains (crystalline phase) results in less pronounced changes in molecular conformation, indicating smaller lattice relaxation, compared to polarons generated in disordered polymer domains (amorphous phase) for which we observe large molecular conformational changes. These conformational changes are directly related to the effective conjugation length of the polymer. Furthermore, we elucidate how blending the P3HT polymer with phenyl C-61 butyric acid methyl ester (PCBM) affects polaron formation in the polymer. We find that blending disturbs polymer crystallinity, reducing the density of polarons that can form upon charge injection at the same potential, whilst the lost capacity is partly restored during post-deposition thermal annealing. Our study provides direct spectroscopic evidence for a lower degree of lattice reorganisation in crystalline (and therefore more planarised) polymers than in conformationally disordered polymers. This observation is consistent with higher charge carrier mobility and better device performance commonly found in crystalline polymer materials.
Issue Date: 27-Dec-2018
Date of Acceptance: 1-Dec-2018
ISSN: 1932-7447
Publisher: American Chemical Society (ACS)
Start Page: 29129
End Page: 29140
Journal / Book Title: The Journal of Physical Chemistry C
Volume: 122
Issue: 51
Copyright Statement: © 2018 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, after peer review and technical editing by the publisher. To access the final edited and published work see
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
Engineering and Physical Sciences Research Council
Funder's Grant Number: EP/K503381/1
Keywords: Science & Technology
Physical Sciences
Chemistry, Physical
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Science & Technology - Other Topics
Materials Science
09 Engineering
03 Chemical Sciences
10 Technology
Physical Chemistry
Publication Status: Published
Embargo Date: 2019-12-05
Article Number: acs.jpcc.8b09706
Online Publication Date: 2018-12-05
Appears in Collections:Physics
Experimental Solid State
Centre for Environmental Policy
Faculty of Natural Sciences

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