Impact of backbone fluorination on nanoscale morphology and excitonic coupling in polythiophenes

Zhongjian Hu, Ryan T. Haws, Zhuping Fei, Pierre Boufflet, Martin Heeney, Peter J. Rossky, David A.Vanden Bout

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

Fluorination represents an important strategy in developing highperformance conjugated polymers for photovoltaic applications. Here, we use regioregular poly(3-ethylhexylthiophene) (P3EHT) and poly(3-ethylhexyl-4-fluorothiophene) (F-P3EHT) as simplified model materials, using single-molecule/aggregate spectroscopy and molecular dynamic simulations, to elucidate the impacts of backbone fluorination on morphology and excitonic coupling on the molecular scale. Despite its high regioregularity, regioregular P3EHT exhibits a rather broad distribution in polymer chain conformation due to the strong steric hindrance of bulky ethylhexyl side chains. This conformational variability results in disordered interchain morphology even between a few chains, prohibiting long-range effective interchain coupling. In stark contrast, the experimental and molecular dynamic calculations reveal that backbone fluorination of F-P3EHT leads to an extended rod-like single-chain conformation and hence highly ordered interchain packing in aggregates. Surprisingly, the ordered and close interchain packing in F-P3EHT does not lead to strong excitonic coupling between the chains but rather to dominant intrachain excitonic coupling that greatly reduces the molecular energetic heterogeneity.
Original languageEnglish (US)
Pages (from-to)5113-5118
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number20
DOIs
StatePublished - May 16 2017
Externally publishedYes

Bibliographical note

Generated from Scopus record by KAUST IRTS on 2023-02-14

ASJC Scopus subject areas

  • General

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