Overcoming phosphorus emitter limitations in PERC Si solar cells by using a gallium-phosphide heteroemitter

The performance of PERC Si solar cells is often limited by recombination in the emitter. We use numerical device simulations to evaluate efficiency limits of different types of phosphorus emitters in an example of a realistic PERC cell. The resulting maximum efficiencies are between 20.5% and 21.2%. The same cell simulated with an emitter made of an n-doped crystalline gallium phosphide layer shows an efficiency limit of 21.6%. This hetero-emitter causes much lower recombination losses than a nearly ideal phosphorus emitter, resulting in a higher V_oc. In addition a lower base doping is necessary which, in turn, reduces the impact of the boron-oxygen complex.