Minority carrier lifetime enhancement in multicrystalline silicon

In this work a new passivation method is proposed for multicrystalline silicon wafers. This method combines the use of porous silicon (PS) and silicon nitride (SiN) coating. SiN thin film is deposited on porous silicon by the plasma-enhanced chemical vapor deposition (PECVD) technique at low temperature and investigated as a passivating and an antireflection coating. We demonstrate that silicon nitride-covered porous silicon is capable of giving an outstanding surface passivation quality on mc-Si. PS-SiN passivation on mc-Si leads to an effective minority carrier lifetime of 100 μs, which is among the highest lifetimes attained on this kind of material. This high effective lifetime results not only from the excellent degree of surface passivation but also from the grain boundaries and bulk passivation. The surface reflectivity was dramatically reduced from 27% for untreated Si wafer to about 5% after PS-SiN coating in the 400–1100 nm wavelength range