Impact of molecular order on polaron formation in conjugated polymers
File(s)
Accepted version
Author(s)
Nightingale, James
Wade, Jessica
Moia, Davide
Nelson, Jenny
Kim, Ji-Seon
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.
Date Issued
2018-12-27
Date Acceptance
2018-12-01
Citation
The Journal of Physical Chemistry C, 2018, 122 (51), pp.29129-29140
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 https://dx.doi.org/10.1021/acs.jpcc.8b09706
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering and Physical Sciences Research Council
Grant Number
EP/K503381/1
EP/L016702/1
Subjects
Science & Technology
Physical Sciences
Technology
Chemistry, Physical
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Chemistry
Science & Technology - Other Topics
Materials Science
HIGH-EFFICIENCY
SOLAR-CELLS
REGIOREGULAR POLY(3-HEXYLTHIOPHENE)
ELECTRICAL-PROPERTIES
CHARGE-TRANSPORT
HIGH-MOBILITY
FILMS
DELOCALIZATION
MORPHOLOGY
DEFECTS
09 Engineering
03 Chemical Sciences
10 Technology
Physical Chemistry
Publication Status
Published
Article Number
acs.jpcc.8b09706
Date Publish Online
2018-12-05