A solution-processable star-shaped molecule for high-performance organic solar cells via alkyl chain engineering and solvent additive

A new star-shaped D–π–A molecule, tris{4-[5′′-(1,1-dicyanobut-1-en-2-yl)-2,2′-bithiophen-5-yl]phenyl}amineN(Ph-2T-DCN-Et)3, with high efficiency potential for photovoltaic applications was synthesized. As compared to its analogue S(TPA-bT-DCN), it showed stronger absorption in the region of 350–450 nm and a lower lying highest occupied molecular energy level (HOMO). Solution-processed organic solar cells (OSCs) based on a blend of N(Ph-2T-DCN-Et)3 and PC70BM resulted in a high PCE of 3.1% without any post-treatment. The PCE of N(Ph-2T-DCN-Et)3 based solar cells was further improved to 3.6% under simulated AM 1.5 by addition of a new additive 4-bromoanisole (BrAni).

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► A new star-shaped D–π–A molecule shows good stability and strong absorption in the region of 350–450 nm.
► PCE of the OSCs based on the molecule as donor and PC70BM as acceptor reached 3.1%.
► The optimized OSCs based on the molecule:PC70BM (1:2 wt.%) with 2 vol.% of BrAni, exhibits a high PCE of 3.6%.