Effect of oxygen ambient during POCl3 diffusion on the performance of silicon solar cells

Phosphorous (P) diffusion is the most important and crucial process in the fabrication of silicon (Si) solar cells. P-diffusion using POCl₃ in a tube furnace reveals the best cell performance because of uniform dopant concentration over the Si surface and gettering of impurities in the substrate. The emitter formation by P-diffusion using POCl₃ diffusion source is a complex and advanced process which provides the gettering and forming the 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 have an impact in the emitter properties. In the present paper, the impact of oxygen (O₂) flow during the diffusion process has been studied. It has been found that, the presence of oxygen during the diffusion process influences the concentration of inactive phosphorous over the surface and the gettering process as well. The optimized flow of oxygen shows, an improvement in lifetime of ~ 24 μsec and an absolute efficiency gain of ~0.3%.