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

Sneyd, Alexander J., Fukui, Tomoya, Palecek, David, Prodhan, Suryoday, Wagner, Isabella, Zhang, Yifan, Sung, Jooyoung, Collins, Sean M., Slater, Thomas J. A. ORCID: https://orcid.org/0000-0003-0372-1551, Andaji-Gamaroudi, Zahra, MacFarlane, Liam R., Garcia-Hernandez, J. Diego, Wang, Linjun, Whittell, George R., Hodgkiss, Justin M., Chen, Kai, Beljonne, David, Manners, Ian, Friend, Richard and Rao, Akshay 2021. Efficient energy transport in an organic semiconductor mediated by transient exciton delocalization. Science Advances 7 (32) 10.1126/sciadv.abh4232

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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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Publisher:	American Association for the Advancement of Science
ISSN:	2375-2548
Date of First Compliant Deposit:	14 February 2022
Last Modified:	17 May 2023 03:50
URI:	https://orca.cardiff.ac.uk/id/eprint/147209

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