A novel mask-free low-temperature rear surface passivation scheme based on PEVCD silicon nitride for high-efficiency silicon solar cells

摘要

The surface passivation properties of plasma-enhanced chemical vapour deposited (PECVD) SiN{sub}x and high-temperature grown SiO{sub}2 films on 1.5-Ωcm p-Si wafers are investigated. In the injection region of about 10{sup}15 cm{sup}-3 both, SiN{sub}x and alnealed SiO{sub}2 films, provide an excellent passivation quality resulting in an effective surface recombination velocity S{sub}(eff) of about 10 cm/s. For lower injection regimes (Δn < 10{sup}14 cm{sup}-3), S{sub}(eff) is significantly lower for alnealed oxide passivated compared to nitride passivated surfaces. Furthermore, results of crystalline silicon solar cells incorporating either films as rear surface passivation are presented. Due to the novel mask-free definition of the rear contact areas based on mechanical means, different (partly etch-resistant) silicon nitride films can be applied. The lower short circuit current of the nitride rear surface passivated solar cells as well as the results of spectral response measurements confirm the superior passivation qualities of the alnealed oxide films in the lower injection region. Nevertheless, efficiencies of 19.5% are reached with SiN{sub}x rear surface passivated solar cells using a simple mask-free low-temperature process.