Electrochemical and Spectroscopic Properties of Boron Dipyrromethene–Thiophene–Triphenylamine-Based Dyes for Dye-Sensitized Solar Cells

Abstract

Because of the current increase in consumption of fossil fuels and its negative impact on the environment, clean energy technologies such as solar cells are highly desirable to address this global energy challenge. Among these, dye-sensitized solar cells (DSSCs) have emerged as potential substitutes to traditional silicon-based solar cells. In this study, a series of boron dipyrromethene (BODIPY)-based dyes (1–5) which contain thiophene and/or triphenylamine (TPA) as redox relays of chromophorebridges are synthesized and characterized using electrochemical and optical spectroscopic methods for their potential applications in DSSCs. Their electrochemical and photophysical properties are investigated and compared with the computational results. DSSCs made of these BODIPY-based dyes exhibit incident photon-to-current conversion efficiencies (IPCE) that correspond to their absorption profiles. BODIPY dye 5 bearing TPA provides the highest power efficiency because of its reversible redox activities, while the dyes bearing thiophene yield a decrease in overall solar cell efficiency because of the irreversible oxidation and electropolymerization of thiophene. Despite their low overall conversion efficiencies, these dyes show interesting structural dependence in their DSSC performance. TiO2 electrodes loaded with these BODIPY dyes are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared analysis to illustrate the surface bonding characteristics of these dyes.