Oligothiophene-linked D–π–A type phenothiazine dyes for dye-sensitized solar cells

Abstract

Three novel phenothiazine dyes (JY31–33) featured oligothiophene π-bridge have been designed, synthesized and applied as photosensitizers for highly efficient dye-sensitized solar cells (DSSCs). The introduction of alkyl chains on oligothiophene π-bridge is found to significantly improve the open-circuit voltage of the resultant device. Phenothiazine bearing a 4-butoxyphenyl group as the secondary donor exhibits a stronger electron-donating ability and a positive acceleration on the short-circuit current density and open-circuit voltage. The dye JY33 containing a secondary donor and two alkyl chains finally gives a high efficiency of 7.48% under the 100 mW cm−2 simulated AM1.5 sunlight, with a short-circuit photocurrent density (Jsc) of 17.18 mA cm−2, an open-circuit photovoltage (Voc) of 742 mV and a fill factor (FF) of 0.59.