Simple-Structured NIR-Absorbing Small-Molecule Acceptors with a Thiazolothiazole Core: Multiple Noncovalent Conformational Locks and D–A Effect for Efficient OSCs

Developing simple-structured and efficient near-infrared
(NIR) absorbing small-molecule acceptors (SMAs) remains of great importance
for commercial applications in organic solar cells (OSCs). Herein,
we construct two novel thiazolothiazole-centered NIR-absorbing SMAs
by alkoxy/alkylthio side chains (TTz3/TTz4) and multiple noncovalent
conformational locks of S···N, S···O,
and S···S. These conformational locks make both simple-structured
SMAs exhibit an extended planar configuration and a red-shifted NIR
absorption in comparison with the SMA with an alkyl side chain (TTz1).
As expected, both SMAs show high-efficiency photovoltaic performance
in the solution-processing OSCs using J71 as a donor. A higher power
conversion efficiency of 8.76% with a low energy loss (0.57 eV) is
obtained in the TTz3-based OSCs. It is the first report on the simple-structured
and efficient NIR-absorbing SMAs, which have great potential applied
in the semitransparent OSCs.