Limitations on the open-circuit voltage imposed by P+ and N+ regions in silicon solar cells

It is shown theoretically and experimentally that the emitter recombination current, which limits the open-circuit voltage of silicon solar cells, can be more easily suppressed in P+N cells than in N+P cells. This result is due to fundamental effects that occur in heavily doped silicon: degeneracy of the majority charge carriers, Auger recombination, and energy-band-gap narrowing. Cell designs to suppress the emitter current are discussed, and experimental data supporting our theoretical analysis are presented.