Extended photo-absorption properties of novel push-pull diphenylpyranylidene molecules and their photovoltaic performance

Two small molecules Y1 and Y2 with diphenylpyranylidene (DPP) as electron-donor and dicyanovinylene or 3-ethylrhodanine as electron-acceptor were designed, synthesized, characterized and applied to organic solar cells as active layer material. Y1 and Y2 showed a wide range of light absorption from 300 to 800 nm in solution and the maximum molar absorption coefficients were up to 30000 to 40000 M(-1)cm(-1). Their optical absorption, electrochemical and photovoltaic properties were also studied. The prepared solar cells based on Y1 or Y2 donor and fullerene acceptor achieved PCE of 1.0% and 0.36%, respectively. The crystallization of Y1 and Y2 in blended active layer with fullerene materials as characterized with X-ray diffraction and atomic force microscope technology.