Theoretical investigation of the optimum design for amorphous silicon based solar cells

A detailed theoretical analysis of a-Si-based solar cells has been performed using a computer simulation model in order to clarify the factors limiting cell performance. It was found that the solar cell performance was affected by low conductivity in the p-layer and the density of D states in the i-layer. The simulation model predicted that the upper limit of a-Si solar cell efficiencies is about 15.0%, which could be obtained for a highly conductive p-layer with a carrier concentration of approximately 10¹⁸ cm^-3 and high-quality a-Si having a low density of D states (1*10¹⁵ cm^-3). It also predicted an optimum bandgap of the i-layer of 1.5 eV, assuming that the N_DB of the i layer is constant with bandgap energy.