This paper presents the detailed performance analysis of single junction silicon and GaAs solar cell using PC1D (Personal computer in one dimension) simulator. The effect of variation in physical and electronic parameters on efficiency of solar cell is determined here. The maximum efficiency achieved for Si is 25. 51% and for GaAs is 28. 96% using PC1D simulator. The results obtained are in accordance with the experimental values. These results are used to optimize the efficiency of single junction solar cells. © Research India Publications.