Analysis of ultrathin high-efficiency silicon solar cells

In this paper we present experimental data on ultrathin silicon wafer solar cells as well as the analytical description of their open-circuit voltage and fill factor. For this we use the analytical model of Fischer and Plagwitz to describe the rear surface recombination that we extend for very low wafer thicknesses. We observe an unexpected drop of the cell voltage at∼40 μm thickness. This decrease cannot be described by the used models and is not reproduced via DESSIS simulations. From the new series resistance formula we can derive an analytical relationship for the fill factor. This allows us to perform a loss analysis of the cells and an optimization of the point contact pitch for different cell thicknesses.