New difluorenylaminocoumarin photosensitizers for dye-sensitized solar cells

Three difluorenylaminocoumarin sensitizers with different π-bridges bearing thiophene ring and cyanoacrylic acid acceptor were synthesized and their photophysical properties and photoelectric conversion efficiency were investigated and compared with counterpart dyes with diphenylaminocoumarin donor. Replacement of benzene with fluorene in the donor unit contributed to superior photovoltaic performance. Among the three π-bridges, the thiophene-phenyl π-bridge improved VOC and JSC, resulting in a DSSC with the best photoelectric conversion efficiency (η = 5.94%, VOC = 670 mV, JSC = 14.53 mA cm−2, and fill factor, FF = 0.61).