Optimizing electrical-optical parameters in TiO₂@CdS@Cd_xCu_1-xSe photoanodes using UV–Vis spectra, J-V curves, and EIS experiments in quantum dot-sensitized solar cells

In this research, photoanodes on the basis of a CdS/CdSe multilayer film, where CdSe-doped with Cu were successfully fabricated and optimized at a 3% doping concentration. The highest performance of quantum dot solar cells is 4.24%. This result is also confirmed by studying the optical and electrical properties of quantum dot solar cells that change with the Cu doping concentration. The enhanced efficiency can be explained by electrical-optical parameters, which are determined from UV–Vis spectra, J–V curves, and EIS experiments. The optical parameters such as absorption density, the band gap, the top of the valence band, and the bottom of the conduction band are estimated based on the Tauc equation and the UV–Vis spectra experiments for optical properties. Moreover, the electrical parameters, such as the shunt resistance and R_ct1 and R_ct2 resistances, are also extracted from J-V curves and the electrochemical impedance spectra experiments for electrical properties. Finally, the obtained results are used to explain the enhanced performance efficiency of devices.