Efficient non-fullerene organic solar cells employing sequentially deposited donor–acceptor layers†
‡ab
Andrew J.
Parnell,
d
Xiao-Ke
Liu,
af
Thomas R.
Hopper,
b
Yutian
Wu,
b
Xiangjian
Wan,
c
Feng
Gao,
f
Neil C.
Greenham,
a
Artem A.
Bakulin,
b
Yongsheng
Chen
*c
and
Richard H.
Friend
*a
Abstract
Non-fullerene acceptors (NFAs) have recently outperformed their fullerene counterparts in binary bulk-heterojunction (BHJ) organic solar cells (OSCs). Further development of NFA OSCs may benefit other novel OSC device structures that alter or extend the standard BHJ concept. Here, we report such a new processing route that forms a BHJ-like morphology between sequentially processed polymer donor and NFA with high power conversion efficiencies in excess of 10%. Both devices show similar charge generation and recombination behaviours, supporting formation of similar BHJ active layers. We correlate the ∼30 meV smaller open-circuit voltage in sq-BHJ devices to more substantial non-radiative recombination by voltage loss analysis. We also determine the exciton diffusion length of benchmark polymer PBDB-T to be 10 ± 3 nm. Our results demonstrate high-efficiency OSC devices using sequential deposition method and provide new opportunities to further improve performance of state-of-the-art OSCs.
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