Both Sides Contacted Silicon Solar Cells. Options for Approaching 26% Efficiency

Recently, we demonstrated an efficiency of 25.8% for a both sides contacted silicon solar cell. These cells were realized on n-type Si featuring a boron-doped p+ emitter at the front surface and a full-area tunnel oxide passivating contact (TOPCon) at the rear surface. In this work, we present a detailed electrical and optical loss analysis of this record cell in order to identify options to further improve the cell performance. Using a simulation-based electrical loss analysis, we are able to identify the main loss mechanisms and optimize e.g. the Si material (thickness, resistivity) as well as the front side emitter. Using an optical loss analysis as well as advanced optical simulations we also evaluated the potential of different light trapping schemes in order to increase the short-circuit current density. Altogether, an efficiency potential clearly beyond 26% is predicted, which is currently being investigated experimentally.