Photoelectrochemical Effects of Guanidinium Thiocyanate on Dye-Sensitized Solar Cell Performance and Stability

In this study, we investigated the photoelectrochemical effect of guanidinium thiocyanate (GuSCN) in the base electrolyte composed of 1-methylbenzimidazole (0.45 M) and 3-methoxypropionitrile on the efficiency of electron injection (Phi(inj)), interfacial recombination kinetics, and photovoltaic performance of dye-sensitized solar cells (DSCs). A significant increase in the photocurrent for DSCs with GuSCN was observed, which was higher than that for DSCs with the base electrolyte. The dependence of the short-circuit photocurrent density on the illumination intensity indicated that the large increase in Phi(inj) could be attributed to the positive shift in the flatband potential of the TiO2 electrode and could increase the electron injection yield. The results from electrochemical impedance spectroscopy (EIS) for DSCs indicated that guanidinium cation chemisorbed on the TiO2, surface Could passivate the surface recombination sites and enhance the electron lifetime in the nanostructured TiO2 film to give an improved open-circuit photovoltage. The photostability of DSCs with 0.1 M GuSCN Could retain over 98% of its initial photoelectric conversion efficiency value under one sun light soaking over the time of 3000 h. It is indicated that GuSCN chemisorbed on TiO2 Surface could keep the interface of DSCs stable.