Ideal Single Diffusion Step Selective Emitters: a Comparison between Theory and Practice

Selective emitters have been an important research subject for crystalline silicon solar cells for decades. It is being used in production for high efficiency solar cells. In this study, selective diffusion barriers have been used to produce selective emitters. This method allows easy control of the lightly doped areas. Experimentally, selectivity has been confirmed and lightly doped sheet resistances have been varied between 50 and 100 ohm/sq. The produced selective emitter cells showed an increase in current of 2%, an increase in voltage of 1%, and an increase in blue IQE response by a factor of 2. PC1D simulations show that the SiNx, optimised for mcSi solar cell efficiency, provides some surface passivation. The simulations show that when bulk passivation and short wavelength transmission can be maintained, further gains will be possible with improved surface passivation. For future research, the challenge is to combine the bulk and surface passivating qualities of SiNx.