Dissolution of electrically inactive phosphorus by low temperature annealing
In this study we investigate the dissolution of electrically inactive phosphorus complexes by low temperature annealing after the POCl3 diffusion process. This has the immediate consequence that the existing near-surface emitter volume SRH recombination can be reduced. Thereby, a significant reduction of emitter saturation current density j0E is achieved without driving the emitter further into the silicon substrate. For short-term temperature treatments well below the POCl3 diffusion temperature, a reduction of up to -60 fA/cm2 has been achieved. This study increases our understanding of the formation and dissolution of electrically inactive phosphorus complexes during post-annealing processes.
Improvement of industrial phosphorus diffused emitters and impact on solar cell efficiencies
In this study, we investigate the importance of the minority carrier lifetime (rp0) and surface recombination velocity (SRV) of industrial n-type emitters in improving emitter performance and improving solar cell efficiency. When emitters with higher τp0 values are applied to Al-BSF and PERC solar cells separately, they show slightly different responses to the increase in τp0. Simulation results indicate that PERC solar cells receive a larger efficiency enhancement with the same increase in τp0 than that for Al-BSF cells. This is due to the fact that emitter recombination can be a major contributor to efficiency loss for solar cell structures like PERC where the rear surface is well passivated by dielectric stacks. Additionally, LDSE cells have a stronger dependence on the surface passivation quality, especially for the PERC structure.
Phosphorus and boron diffusion gettering of iron in monocrystalline silicon
We have studied experimentally the phosphorus diffusion gettering (PDG) of iron in monocrystalline silicon at the temperature range of 650–800 °C. Our results fill the lack of data at low temperatures so that we can obtain a reliable segregation coefficient for iron between a phosphorus diffused layer and bulk silicon. The improved segregation coefficient is verified by time dependent PDG simulations. Comparison of the PDG to boron diffusion gettering (BDG) in the same temperature range shows PDG to be only slightly more effective than BDG. In general, we found that BDG requires more carefully designed processing conditions than PDG to reach a high gettering efficiency.