Performance Enhancement of CGS/CIGS Thin Flm Tandem Solar Cell Using Different Buffer Layers

In this paper, CGS/CIGS ultra-thin film tandem photovoltaic cells with different buffer layers (CdS, ZnSe and ZnS) were examined using Silvaco-Atlas under standard AM1.5G illumination, at 300 K temperature. After examining the performance of these cells, ZnS buffer layer used in both bottom and top cell showed the best conversion efficiency of 26.56%. Following confirmation of the obtained results, and for the sake to enhance this cell and its power conversion efficiency, the absorber layers of bottom and top cells were improved by optimization their band gaps, thicknesses and doping densities, which considered as key parameters. The proposed CGS/CIGS tandem cell with the ZnS buffer layer achieved a conversion efficiency of 30.43% when the optimum thicknesses were determined as 205 and 375 nm, doping densities as 2 × 10¹⁶ and 4 × 10¹⁵ cm^− 3 and bandgap energies as 1.69 and 1.27 eV for absorber layers of top (CGS) and bottom (CIGS) cells, respectively. Also the results exhibited that the decreasing of operating temperature can improve the cell performance. With a temperature of 280 K, a very important efficiency (η = 32.41%) of CGS/CIGS tandem cell can be achieved.