nc-SiC by PECVD for High-Temperature Passivating Contacts

This work investigates the potential of nanocrystalline silicon carbide (nc-SiC) films as transparent passivating contacts for high-efficiency solar cells. A plasma-enhanced chemical vapor deposition process for high hydrogen radical density was developed to fabricate nc-SiC films. The influence of phosphorus (P) doping and thermal treatment on the structural, compositional, and electrical properties of these films was investigated. Increased doping reduced the contact resistance but also negatively affected the open circuit voltage ($iV_{\text{oc}}$). We identified a set of parameters that provided a compromise between conductivity and passivation, resulting in a maximum $iV_{\text{oc}}$ of 708 mV on textured surfaces with a contact resistance of around 100 $\mathrm{m}\mathrm{\Omega }\mathrm{c}\mathrm{m}^{2}\,$. In addition, nc-SiC exhibited superior ultraviolet transparency compared to poly silicon (poly-Si) and crystalline silicon (c-Si), with an absorption coefficient of $3\times 10^{5}\; \text{cm}^{-1}$ at 350 nm, lower than the typical $1\times 10^{6}\; \text{cm}^{-1}$ for poly-Si and c-Si.