Transparent silicon carbide/tunnel SiO₂ passivation for c-Si solar cell front side

Abstract

N-type microcrystalline silicon carbide (μc-SiC:H(n)) is a wide bandgap material that is very promising for the use on the front side of crystalline silicon (c-Si) solar cells. It offers a high optical transparency and a suitable refractive index that reduces parasitic absorption and reflection losses, respectively. In this work, we investigate the potential of hot wire chemical vapor deposition (HWCVD)–grown μc-SiC:H(n) for c-Si solar cells with interdigitated back contacts (IBC). We demonstrate outstanding passivation quality of μc-SiC:H(n) on tunnel oxide (SiO₂)–passivated c-Si with an implied open-circuit voltage of 742 mV and a saturation current density of 3.6 fA/cm². This excellent passivation quality is achieved directly after the HWCVD deposition of μc-SiC:H(n) at 250°C heater temperature without any further treatments like recrystallization or hydrogenation. Additionally, we developed magnesium fluoride (MgF₂)/silicon nitride (SiN_x:H)/silicon carbide antireflection coatings that reduce optical losses on the front side to only 0.47 mA/cm² with MgF₂/SiN_x:H/μc-SiC:H(n) and 0.62 mA/cm² with MgF₂/μc-SiC:H(n). Finally, calculations with Sentaurus TCAD simulation using MgF₂/μc-SiC:H(n)/SiO₂/c-Si as front side layer stack in an IBC solar cell reveal a short-circuit current density of 42.2 mA/cm², an open-circuit voltage of 738 mV, a fill factor of 85.2% and a maximum power conversion efficiency of 26.6%.