Organic donor materials based on bis(arylene ethynylene)s for bulk heterojunction organic solar cells with high V_OC values

A series of purely organic small molecules 1-4 based on bis(arylene ethynylene)s with various electron-rich aromatic bridges, such as benzene, cyclopentadithiophene (CDT), and diphenyl(p-tolyl)amine, were synthesized by a Sonogashira coupling reaction. Their optical, electronic, and electrochemical properties were fully characterized. The photovoltaic properties of these molecules as donor materials and [6,6]-phenyl-C₇₁-butyric acid methyl ester as an acceptor material in solution-processed bulk heterojunction devices were studied. Among them, CDT-bridged molecule 2 exhibited the best photovoltaic performance and achieved a power conversion efficiency of 3.28%. In addition, the photovoltaic efficiencies of these molecules are higher than their corresponding platinum-containing counterparts, probably owing to their stronger light absorption and improved open-circuit voltage.