Passivation effect of ultra-thin SiNx films formed by catalytic chemical vapor deposition for crystalline silicon surface

Abstract

We propose a way of replacing silicon dioxide (SiO2) films in tunnel oxide passivated contact (TOPCon) solar cells by ultra-thin Si nitride (SiNx) films. We deposit SiNx films on n-type crystalline Si (c-Si) wafers by catalytic chemical vapor deposition (Cat-CVD), by which we avoid a plasma damage to the surface of c-Si. Thin (<5 nm) SiNx films can be deposited with good controllability by tuning the deposition conditions. To improve the passivation quality of SiNx films, hydrogen treatment was performed onto the SiNx-coated c-Si surfaces. Their effective minority carrier lifetime (τeff) can be improved up to >1 ms by the hydrogen treatment for the samples containing SiNx with a proper refractive indices and >10-nm-thick n-type amorphous Si (n-a-Si). The ultra-thin SiNx films have sufficiently high passivation ability and have the required level for the passivation layers of rear-side contact in the TOPCon-like c-Si solar cells.