Optimized phosphorus diffusion process and performance improvement of c-Si solar cell by eliminating SiP precipitates in the emitter

Phosphorus diffusion is the most common way to form the emitter for p-type crystalline silicon (c-Si) based solar cells. The emitter region is usually known as dead layer, which may result in the band gap narrowing and higher carrier recombination. In this work we have demonstrated that the SiP precipitates are usually formed in the emitter of c-Si during phosphorus diffusion process, which can become the recombination centers for the minority carriers and therefore degrade the performance of c-Si solar cells. By a post-anneal treatment or a higher temperature diffusion with lower concentration of phosphorus source, the SiP precipitates in the emitter region can be effectively eliminated. As a result, the corresponding solar cell based on the modified phosphorus diffusion process exhibits a higher conversion efficiency than the conventional one by a value of 0.2%.