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Direct visualization of the charge transfer state dynamics in dilute-donor organic photovoltaic blends

Abstract:
The interconversion dynamics between charge transfer state charges (CTCs) and separated charges (SCs) is still an unresolved issue in the field of organic photovoltaics. Here, a transient absorption spectroscopy (TAS) study of a thermally evaporated small-molecule:fullerene system (α6T:C60) in different morphologies (dilute intermixed and phase separated) is presented. Spectral decomposition reveals two charge species with distinct absorption characteristics and different dynamics. Using time-dependent density functional theory, these species are identified as CTCs and SCs, where the spectral differences arise from broken symmetry in the charge transfer state that turns forbidden transitions into allowed ones. Based on this assignment, a kinetic model is formulated allowing the characterization of the charge generation, separation, and recombination mechanisms. We find that SCs are either formed directly from excitons within a few picoseconds or more slowly (~30–80 ps) from reversible splitting of CTCs. These findings constitute the first unambiguous observation of spectrally resolved CTCs and SCs.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1038/s41467-024-53694-4

Authors


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Role:
Author
ORCID:
0000-0001-5947-5500
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Institution:
University of Oxford
Division:
MPLS
Department:
Physics
Sub department:
Condensed Matter Physics
Role:
Author
ORCID:
0000-0002-9888-6262


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Funder identifier:
https://ror.org/00yjd3n13


Publisher:
Springer Nature
Journal:
Nature Communications More from this journal
Volume:
15
Issue:
1
Article number:
9851
Publication date:
2024-11-14
Acceptance date:
2024-10-18
DOI:
EISSN:
2041-1723


Language:
English
Pubs id:
2062700
Local pid:
pubs:2062700
Source identifiers:
2419375
Deposit date:
2024-11-14

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