Singlet and triplet excited-state dynamics of a nonfullerene electron acceptor Y6

14 July 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Understanding the excited-state dynamics of nonfullerene electron acceptors is essential for further improvement of organic solar cells. Herein, we investigated the singlet and triplet excited-state dynamics in Y6, a novel nonfullerene acceptor, using transient absorption spectroscopy. We found that pristine Y6 films show biphasic singlet exciton decay kinetics with decay constants of ~220 ps and ~1200 ps, which is the origin of the large discrepancies in the previously reported exciton lifetimes in the solid state. The majority of the Y6 singlet excitons decayed with the faster (~220 ps) component, whereas a clear photoluminescence with the slower (~1200 ps) component was observed. Y6 singlet excitons undergo fast diffusion in the crystalline domains, resulting in fast singlet–singlet exciton annihilation, after which ultrafast triplet formation, assigned to singlet fission from higher excited singlet states, is observed.


exciton diffusion
organic solar cell
photon upconversion
singlet–singlet exciton annihilation
singlet fission
transient absorption spectroscopy

Supplementary materials

Supporting Information
Supporting Information for Singlet and triplet excited-state dynamics of a nonfullerene acceptor Y6


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