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

DOI: 10.1126/sciadv.abh4232 DOI Help

Authors: Alexander J. Sneyd (University of Cambridge) , Tomoya Fukui (University of Victoria; University of Bristol) , David Paleček (University of Cambridge) , Suryoday Prodhan (University of Mons) , Isabella Wagner (Victoria University of Wellington) , Yifan Zhang (University of Victoria; University of Bristol,) , Jooyoung Sung (University of Cambridge) , Sean M. Collins (University of Leeds) , Thomas J. A. Slater (Diamond Light Source) , Zahra Andaji-Garmaroudi (University of Cambridge) , Liam R. Macfarlane (University of Victoria; University of Bristol) , J. Diego Garcia-Hernandez (University of Victoria; University of Bristol) , Linjun Wang (Zhejiang University) , George R. Whittell (University of Bristol) , Justin M. Hodgkiss (Victoria University of Wellington) , Kai Chen (Victoria University of Wellington; The Dodd-Walls Centre for Photonic and Quantum Technologies) , David Beljonne (University of Mons) , Ian Manners (University of Cambridge; University of Bristol) , Richard H. Friend (University of Cambridge) , Akshay Rao (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Science Advances , VOL 7

State: Published (Approved)
Published: August 2021
Diamond Proposal Number(s): 25140

Open Access Open Access

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.

Diamond Keywords: Semiconductors

Subject Areas: Materials, Physics, Energy

Diamond Offline Facilities: Electron Physical Sciences Imaging Centre (ePSIC)
Instruments: E02-JEM ARM 300CF

Added On: 09/08/2021 14:00

Documents:
eabh4232.full.pdf

Discipline Tags:

Materials Science Energy Materials Physics Surfaces interfaces and thin films

Technical Tags:

Microscopy Electron Microscopy (EM) Scanning Electron Microscopy (SEM)