Development of Transparent and High-Voltage Electrolyte Using Binary Redox Couples for Dye-Sensitized Solar Cells

Abstract

The conventional iodine-based electrolytes of DSSCs has several limitations such as ~30% absorption of visible light in the range of 300 to 500 nm wavelength by itself and large potential difference between the Fermi level of I−/I3− and the HOMO level of dye, which creates negative impact on both transparent and high-voltage DSSCs. In this work, a series of transparent electrolytes are prepared with the variation of additives of I2, LiI, GuSCN (guanidine thiocyanate)/GuNO3 and Br2 for high transparent and high voltage DSSCs. From the results of this study, it is found that the use of optimized electrolyte with binary redox couples (I, Br)/(I3,I2Br) (instead of single I/I3 couple), 0.003 M Br2, 0.01 M LiI, and 0.1 M GuNO3 contributes to increase the transmittance of ~25% compared with the conventional electrolyte as the content of I3 decreased significantly in binary redox system. Furthermore, the downward shifting in Fermi level of the binary redox system induces the enhancement of the open circuit voltage (Voc) of the cell by ca. 120 mV compared with the conventional electrolyte. The devices with the optimized binary redox system achieved a high efficiency of ~ 6.22 % with a least sacrifice compared with the conventional one. It indicates that the present study could play an essential role to fabricate high voltage and transparent DSSCs for the application of see-through photovoltaic windows.