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

A new star-shaped D-pi-A molecule, tris{4-[5 ''-(1,1-dicyanobut-1-en-2-yl)-2,2'-bithiophen-5-yl] phenyl} amine N(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). (C) 2012 Elsevier B.V. All rights reserved.