This study aims to improve the electrical performances of the GaxIn1-xP single junction solar cell. To this objective, a single-junction solar cell GaxIn1-xP has been simulated with different doping concentrations and thicknesses of the emitter and base region in order to improve its conversion efficiency. The simulations have been done taking into account the optical, electrical and physical properties of the GaxIn1-xP according to the indium composition. The physical models such as the radiative, Auger and Shockley–Read–Hall (SRH) recombination were also considered. The optimized single junction Ga0.04In0.96P (1.39 eV) solar cell structure achieved, showed, under standard conditions (1-sun, AM1.5, 300 K), a maximum conversion efficiency of 23.73%. Moreover, the effects of the thickness and the doping concentration of each region on the electrical parameters of the Ga0.04In0.96P solar cell were also studied.