Upgrade PERC with TOPCon: Efficiency Potential by Taking into Account the Electrical Gains and Optical Losses

Passivating contacts like the tunnel-oxide passivating contact (TOPCon) technology are promising candidates for a next generation of silicon solar cells and are currently being implemented in industrial cell manufacturing. Since there are a number of possibilities how to integrate TOPCon via various cell architectures into industrial cells, it demands educated decisions to direct R&D efforts into the most promising candidates, i.e. creating a roadmap based on expected performance gains. This work shows how to thoroughly quantify the performance potential via numerical device simulation. Focus of this work is an evolutionary upgrade of the current PERC technology, that is introducing TOPCon on the rear and front side to reduce contact recombination but sticking to a p-type wafer and phosphorus diffused emitter. We specifically highlight the need to fully consider not only the electrical gains, but also the substantial optical losses through parasitic absorption in the poly silicon layers. A moderate efficiency gain of below 1%abs with respect to the current PERC technology is found. However, this gain may, counterintuitively, increase in future along with an improved PERC technology, if emitter and bulk recombination as the dominating losses can be reduced.