Silicon nitride at high deposition rate by Hot Wire Chemical Vapor Deposition as passivating and antireflection layer on multicrystalline silicon solar cells

A new regime of high rate deposition of near-stoichiometric silicon nitride by Hot Wire Chemical Vapor Deposition was investigated. The layers were tested on multicrystalline silicon solar cells in order to assess their antireflection and passivation properties. The present design of the filament arrangement and the showerhead gas supply system allows for virtually unlimited scale-up and deposition rates of around 3 nm/s were obtained. By varying the SiH4 flow, the refractive index at 630 nm (n) could be controlled from 1.90 ± 0.05 to 2.12 ± 0.05, and the extinction coefficient at 400 nm (k) was < 0.007 for all films of interest. The cells had state-of-the-art values for all photovoltaic parameters, similar to cells with a conventional SiNx antireflection coating. An efficiency of 14.3% was reached using HWCVD SiNx for multicrystalline Si solar cells with an industrial emitter.