Silicon nitride/silicon oxide interlayers for solar cell passivating contacts based on PECVD amorphous silicon

This Letter demonstrates improved passivating contacts for silicon solar cells consisting of doped silicon films together with tunnelling dielectric layers. An improvement is demonstrated by replacing the commonly used silicon oxide interfacial layer with a silicon nitride/silicon oxide double interfacial layer. The paper describes the optimization of such contacts, including doping of a PECVD intrinsic a-Si: H film by means of a thermal POCl3 diffusion process and an exploration of the effect of the refractive index of the SiNx. The n(+) silicon passivating contact with SiNx/SiOx double layer achieves a better result than a single SiNx or SiOx layer, giving a recombination current parameter of similar to 7 fA/cm(2) and a contact resistivity of similar to 0.005 Omega cm(2), respectively. These self-passivating electron-selective contacts open the way to high efficiency silicon solar cells. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim