The multi-Junction solar cell technique was suggested for achieving high efficiency. This paper describes the simulation of a solar cell for double junction CGS/CIGS solar cell using Silvaco ATLAS software. The simulated device performance was demonstrated in the form of current-voltage (I-V) characteristics and quantum efficiency (QE). By simulation of the tow solar cell, we have obtained for solar the top cell maximum opencircuit voltage 1.15V, a short circuit current density of 18.74 mA, a fill factor (FF) of 87.79 % and an efficiency of 18.27% and for the bottom solar cell is maximum opencircuit voltage 0.57 V, a short circuit current density of 21.52 mA, a fill factor (FF) of 82.82% and an efficiency of 10.26%. For the Tandem whose sub-cells are tied in parallel, the maximum open-circuit voltage 1.16V, a short circuit current density of 29 mA, a fill factor (FF) of 83.06% and an efficiency of 28.11%.

The CIGS thin-film solar cells Solar cells are regarded as one of the most promising photovoltaic technologies. They have the advantage of fast and low-cost manufacturing by depositing several thin layers. In this work, a numerical simulation was made to compare the effect of different buffer layers (CdS, ZnS, ZnSe, and In2S3) on the performance of CIGS solar cells using Silvaco Tcad 2D software. The results show that each buffer layer influences the performance of the cell. Therefore, our results suggest that the ZnS material as a buffer layers has better performance for our cell (Jsc=37.0252mAcm2, Voc=1,281, FF=88,01 , ƞ=20,88).