In this article, based on numerical simulation, SCAPS-1D software was used to investigate the influence of theMoSe2 layer at the CIGS/Mo interface on the performance of the CIGS solar cell. Analysis of the effect of the thickness and bandgap width of the MoSe2 layer revealed that optimum performance is obtained with a MoSe2 layer of 0.030 μm thickness and a bandgap of 1.3 eV. Subsequently, the J-V characteristic and quantum efficiency of the CIGS solar cell with optimal layer parameters MoSe2 were compared with the cell without MoSe2. This analysis demonstrated that the presence of this optimized MoSe2 layer at the CIGS/Mo interface improves the electrical performance of the solar cell.