Low Temperature Back Surface Passivation of Solar Cells by Plasma Silicon Nitride

Abstract

A novel low temperature technique for back surface passivation of solar cells is introduced, which is based upon a small-area ohmic contact grid in combination with plasma silicon nitride deposited on the silicon surface between the grid fingers. The passivation effect was demonstrated theoretically and experimentally for MIS inversion layer solar cells with substrate thicknesses ranging from 330m down to 80µm. A 12% increase in efficiency could be achieved for 33µm thick cells with back surface passivation compared to those with a continuous ohmic back contact. This improvement could be attributed to a higher spectral response at longer wavelengths as well as to a reduced dark saturation current. The experimental results are in good agreement with the theoretical calculations using a one-dimensional model.