Factors affecting the open circuit voltage in amorphous silicon solar cells

The authors examine, by means of numerical modeling, the factors which determine and limit the open circuit voltage of a-Si p-i-n solar cells. It is found that a good front contact which blocks minority carriers enhances the open circuit voltage when the acceptor doping in the emitter is low. However, these effects do not lead to as much improvement of the solar cell conversion efficiency as might be expected because of a decrease in the fill factor which accompanies the increase in V_oc. The authors also show that tail state recombination is an important parameter which limits V_oc