In this study, the effect of phosphorous concentration has been investigated on performance of porous silicon solar cells. For this purpose, silicon substrates were etched into aqueous etching solution containing hydrofluoric acid / hydrogen peroxide with molar ratios 0.82, 0.87 and 0.89 via metal-assisted chemical etching. Surface characteristics were studied by optical microscopy, field-emission electron microscopy and antireflection analysis. In the following, solar cells were fabricated by phosphorous diffusion into optimized porous silicon substrate which phosphorous concentrations had values of 3%, 9%, and 15%. The result presented that in 0.82 molar ratio, the etched silicon had uniform porosities whose sizes were nearly to Ag nano-particles. The reflectance of this substrate was decreased to 11% and was the best substrate for absorbing incident light. Survey of fabricated solar cell performance showed 98% increasing of short circuit current in the solar cell which was made by P₂O₅ 3%. This concentration due to is near the solubility of phosphorous in silicon, caused the increasing efficiency to 10.6%.