It was recalled that P diffusion was the most important process in the fabrication of silicon solar cells from p-type Si substrates. P-diffusion using phosphorous-oxychloride (POCl3) as a precursor in a tube furnace had given the best cell performance because of uniform dopant concentration all over the Si surface and gettering of metallic impurities present in the substrate. The emitter formation by using POCl3 provided gettering and forming of an unwanted dead layer on the front surface due to inactive phosphorous. Along with temperature, the ambient conditions during the diffusion process, such as gas flow rates and their composition, flow kinetics also had an impact on the emitter properties. Here, the impact of O2 flow, during the diffusion process, on emitter formation and solar cell performance were studied. It was found that the presence of oxygen during the diffusion process influenced the concentration of inactive phosphorous over the surface and the gettering process as well. The optimized oxygen flow showed an improvement in the effective minority carrier lifetime of ∼24 μs after diffusion and an absolute efficiency gain of 0.2% at pilot production.

Effect of Oxygen Ambient during Phosphorous Diffusion on Silicon Solar Cell. D.Kumar, S.Saravanan, P.Suratkar: Journal of Renewable Sustainable Energy, 2012, 4[3], 033105