An expanded conjugation photosensitizer with two different adsorbing groups for solar cells

Three novel hemicyanine derivatives bearing different electron donors, 2-[4-N, N-dimethylaminostyryl]-β-naphthothiazolium propylsulfonate (dye 1), 2-[4-N, N-diethylaminostyryl]-β-naphthothiazolium propylsulfonate (dye 2) and 2-[2-hydroxyl-4-N, N-diethylaminostyryl]-β-naphthothiazolium propylsulfonate (dye 3), were designed and synthesized for use in dye-sensitized mesoporous TiO2 solar cells. Their visible light absorption, luminescence emission, electrochemical properties, and photoelectrochemical properties were systematically studied. Upon comparison, dye 3 was found to be the best sensitizer. Experimental data show that introduction of a hydroxyl group can greatly enhance the electron injection efficiency, moreover, this enhancement can greatly override the unfavourable factor originated from the decrease of the adsorption amount of dye 3. Additionally bearing the hydroxyl group, the dye 3 sensitized solar cell gained remarkably high photoelectric conversion yield of 6.3% under illumination of 80.0 mW cm−2 white light from a Xe lamp.