This work, using a numerical code PC-lD, describes the effects of surface and bulk recombination on the performance of p + n indium phosphide solar cells. It is shown that surface recombination velocity and minority carrier diffusion lengths play a dominant role in controlling the efficiency of p + n cells. In order to have an acceptable series resistance, a p + n cell must have an emitter that is thicker than a n + p cell emitter. Consequently the performance of a p + n cell is more sensitive to the front surface recombination velocity. Improved surface and bulk recombination parameters can lead to cell efficiencies in excess of 24% AMO at 25°C.