Novel hemicyanine sensitizers based on benzothiazole-indole for dye-sensitized solar cells: Synthesis, optoelectrical characterization and efficiency of solar cell

Abstract

Synthesis, characterization, and photovoltaic properties of three new hemicyanine sensitizers based benzothiazole-indoline (HC-TH, HC-IND1 and HC-IND2) were tested in DSSC with TiO2 film. These sensitizers have a higher molar absorption coefficient, and thus have better light harvesting properties. Electrochemical, theoretical, and spectroscopic methods were used to calculate energy levels of the dye molecules both in the excited state and in the ground state. The results obtained from the spectroscopy and Tafel studies show a marked increase in overall photoelectro-chemical cell output with Br-substitute at p-position in the hemicyanine sensitizer. Interestingly, HC-IND2 showed absorption of UV–Vis at a longer wavelength than HC-IND1 and HC-TH. This structural feature, as well as optical properties, would result in an improved efficiency of DSSC with a better photovoltaic output (4.01%) solar to electricity conversion efficiency compared to HC-IND1 and HC-TH.