Analysis of laser-doped phosphorus emitters

Heavily doped emitters with low saturation current density are of particular interest for selective emitter solar cells. These emitters can be obtained by laser doping through the PSG layer formed after thermal diffusion from POCl3 gas. The experimental results show that in contrast to purely POCl3 furnace-diffused emitters, the saturation current density of heavily laser-doped emitters decreases as sheet resistance decreases. This peculiar behavior was explained by both qualitative analysis and numerical simulations. Surface recombination velocities were also investigated and revealed that while lightly laser-doped emitters were sensitive to surface state, heavily laser-doped emitters saturation current densities were only weakly dependant on recombination at the surface. Laser-doped selective emitter solar cells were also processed and featured an absolute overall gain of 0.6% in efficiency.