Efficiency improvement of dye-sensitized solar cells using Cu,Co/TiO₂ photoelectrodes doped by applying ultrasonic treatment

In this study, a dye-sensitized solar cell (DSSC) doped with Cu, Co was fabricated by simultaneously sonicating TiO₂ and a trace amount of a transition metal precursor. The cavitation bubbles occurred during sonication resulted in defects on the surface of the TiO₂ particles. As ultrasonic treatment was applied, doping was successfully performed even though Cu and Co were added in small amounts. The surface activation of TiO₂ was confirmed by performing XPS, and the doping of Cu and Co was verified by employing TEM-EDS analysis. Fabricating doped TiO₂ as a photoelectrode and analyzing it using UV–Vis spectroscopy demonstrated that the amount of dye adsorption was significantly increased. In addition, the reduction in electron transfer resistance was confirmed by applying EIS, and the factors contributing to efficiency improvement were investigated by calculating the chemical capacitance and recombination resistance. The maximum energy-conversion efficiency of the DSSCs fabricated by TiO₂ which doped with Cu and Co by ultrasonic treatment was 4.16%, and that of the DSSCs fabricated with TiO₂ not doped with a transition metal was measured at 2.93%. As above, TiO₂ was doped with a transition metal using ultrasonic treatment, contributing to the improvement of the performance of the TiO₂ photoelectrode.