SiOyNx/SiNx stack: a promising surface passivation layer for high-efficiency and potential-induced degradation resistant mc-silicon solar cells

摘要

A thin SiOyNx film was inserted below a conventional SiNx antireflection coating used in c-Si solar cells in order to improve the surface passivation and the solar cell's resistance to potential-induced degradation (PID). The effect of varying the flow ratio of the N2O and SiH4 precursors and the deposition temperature for the SiOyNx thin film upon material properties were systematically investigated. An excellent surface passivation was obtained on FZ p-type polished silicon wafers, with the best results obtained with a SiOyNx film deposited at a very low temperature of 130 degrees C and with an optical refractive index of 1.8. In the SiOyNx/SiNx stack structure, a SiOyNx film with similar to 6nm thickness is sufficient to provide excellent surface passivation with an effective surface recombination velocity S-eff<2cm/s. Furthermore, we applied the optimized SiOyNx/SiNx stack on multicrystalline Si solar cells as a surface passivation and antireflection coating, resulting in a 0.5% absolute average conversion efficiency gain compared with that of reference cells with conventional SiNx coating. Moreover, the cells with the SiOyNx/SiNx stack layers show a significant increase in their resistance to PID. Nearly zero degradation in shunt resistance was obtained after 24h in a PID test, while a single SiNx-coated silicon solar cell showed almost 50% degradation after 24h. Copyright (c) 2016 John Wiley & Sons, Ltd.