Theory and experiments on the back side reflectance of silicon wafer solar cells

New passivation layers for the back side of silicon solar cells have to show high performance in terms of electrical passivation as well as high internal reflectivity. This optical performance is often shown as values for the back side reflectance R-b which describes the rear internal reflection. In this paper, we investigate in detail the meaning of this single-value parameter, its correct determination and the use in one-dimensional simulations with PCID. The free-carrier-absorption (FCA) as non-carrier-generating absorption channel is analyzed for solar cells with varying thickness. We apply the optical analysis to samples with different thickness, silicon oxide layer thickness, rear side topography as well as passivation layers (SiO2, SiNx, SiC and stack systems). Additionally, the optical influence of the laser fired contacts (LFC) process is experimentally investigated. Finally, we show that with correct parameters, the one-dimensional simulation of very thin silicon solar cells can successfully be performed. Copyright (C) 2007 John Wiley & Sons, Ltd.