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Non-Fused Non-Fullerene Acceptors with an A-D-A'-D-A Framework and a Benzothiadiazole Core for High-Performance Organic Solar Cells.

Non-fullerene acceptors (NFAs) have contributed significantly to the progress of organic solar cells (OSCs). However, most NFAs featured a large fused-ring backbone, which usually require tedious multiple-step synthesis and are not applicable to commercial application. An alternative strategy is to develop non-fused NFAs, which possess synthetic simplicity and facile tunability in optoelectronic properties and solid-state microstructures. In this work, we report two non-fused NFAs, BTCIC and BTCIC-4Cl, based on an A-D-A'-D-A architecture, which possess the same electron-deficient benzothiadiazole central core but different electron-withdrawing terminal groups. The optical properties, energy levels, and molecular crystallinities were finely tuned by changing the terminal groups. Moreover, a decent power conversion efficiency of 9.3% and 10.5% has been achieved by BTCIC and BTCIC-4Cl, respectively, by blending them with an appropriate polymer donor. These results demonstrate the potential of A-D-A'-D-A type non-fused NFAs for high-performance OSCs. Further development of non-fused NFAs will be very fruitful by employing appropriate building blocks and via side chain optimizations.