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Long-lived and disorder-free charge transfer states enable endothermic charge separation in efficient non-fullerene organic solar cells.

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Chan, Christopher CS  ORCID logo  https://orcid.org/0000-0001-6725-6463
Ma, Chao 
Paleček, David 

Abstract

Organic solar cells based on non-fullerene acceptors can show high charge generation yields despite near-zero donor-acceptor energy offsets to drive charge separation and overcome the mutual Coulomb attraction between electron and hole. Here, we use time-resolved optical spectroscopy to show that free charges in these systems are generated by thermally activated dissociation of interfacial charge-transfer states that occurs over hundreds of picoseconds at room temperature, three orders of magnitude slower than comparable fullerene-based systems. Upon free electron-hole encounters at later times, both charge-transfer states and emissive excitons are regenerated, thus setting up an equilibrium between excitons, charge-transfer states and free charges. Our results suggest that the formation of long-lived and disorder-free charge-transfer states in these systems enables them to operate closely to quasi-thermodynamic conditions with no requirement for energy offsets to drive interfacial charge separation and achieve suppressed non-radiative recombination.

Description

Keywords

40 Engineering, 3403 Macromolecular and Materials Chemistry, 4016 Materials Engineering, 34 Chemical Sciences

Journal Title

Nat Commun

Conference Name

Journal ISSN

2041-1723
2041-1723

Volume Title

11

Publisher

Springer Science and Business Media LLC

Rights

All rights reserved
Sponsorship
Engineering and Physical Sciences Research Council (EP/M006360/1)
EPSRC (1642195)
EPSRC (1642195)