Well-controlled thieno[3,4-c]pyrrole-4,6-(5H)-dione based conjugated polymers for high performance organic photovoltaic cells with the power conversion efficiency exceeding 9%

We have synthesized a series of conjugated D-pi-A copolymers, PT-ttTPD and PBT-ttTPD, based on a (5-hexyltridecyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (ttTPD) acceptor unit in order to develop better photovoltaic polymers based on the TPD moiety: an epsilon-branched alkyl side chain on the TPD unit was coupled with 6-alkyl-thieno[3,2-b]thiophene (tt) pi-bridge molecules. The Stille polymerization of the brominated ttTPD and stannylated simple thiophene (T) finally gave a promising PT-ttTPD polymer showing well-ordered inter-chain orientation in the BHJ active layer. PT-ttTPD-based OPVs exhibited a highest power conversion efficiency (PCE) of 9.21% (V-OC = 0.86 V, J(SC) = 15.30 mA cm(-2), FF = 70%).