Efficient energy transport in an organic semiconductor mediated by transient exciton delocalization

Alexander J. Sneyd, Tomoya Fukui, David Paleček, Suryoday Prodhan, Isabella Wagner, Yifan Zhang, Jooyoung Sung, Sean M. Collins, Thomas J.A. Slater, Zahra Andaji-Garmaroudi, Liam R. MacFarlane, J. Diego Garcia-Hernandez, Linjun Wang, George R. Whittell, Justin M. Hodgkiss, Kai Chen, David Beljonne, Ian Manners, Richard H. Friend, Akshay Rao

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82 Scopus citations

Abstract

Efficient energy transport is desirable in organic semiconductor (OSC) devices. However, photogenerated excitons in OSC films mostly occupy highly localized states, limiting exciton diffusion coefficients to below ~10−2 cm2/s and diffusion lengths below ~50 nm. We use ultrafast optical microscopy and nonadiabatic molecular dynamics simulations to study well-ordered poly(3-hexylthiophene) nanofiber films prepared using living crystallization-driven self-assembly, and reveal a highly efficient energy transport regime: transient exciton delocalization, where energy exchange with vibrational modes allows excitons to temporarily re-access spatially extended states under equilibrium conditions. We show that this enables exciton diffusion constants up to 1.1 ± 0.1 cm2/s and diffusion lengths of 300 ± 50 nm. Our results reveal the dynamic interplay between localized and delocalized exciton configurations at equilibrium conditions, calling for a re-evaluation of exciton dynamics and suggesting design rules to engineer efficient energy transport in OSC device architectures not based on restrictive bulk heterojunctions.

Original languageEnglish
Article numbereabh4232
JournalScience Advances
Volume7
Issue number32
DOIs
StatePublished - Aug 2021

Bibliographical note

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Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY)..

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