Silicon oxide/silicon nitride stack system for 20% efficient silicon solar cells

Thick thermal oxides of more than 100 nm are commonly used for the production of high-efficiency silicon solar cells from mono- and multicrystalline silicon and have led to the highest conversion efficiencies reported so far. This superior performance of oxides is due to the very good surface passivation by the reduction of the density of interface states. The process to achieve such thick oxides are usually performed at high temperatures for a long time. In this paper we investigate different rear stack systems of a thin thermally grown silicon oxide and PECVD silicon nitride and PECVD silicon oxide layers for rear surface passivation. In a comparatively easy high-efficiency process with laser fired rear contacts (LFC) efficiencies above 20% for FZ-Si and 18.2% for multicrystalline silicon were achieved.