Numerical Simulation of Carrier-Selective Electron Contacts Featuring Tunnel Oxides

Recently, n-type Si solar cells featuring tunnel-oxide-passivated contacts have achieved remarkable conversion efficiencies of up to 24.9%. Different approaches concerning the doped Si layer, which can be amorphous, polycrystalline, or partially crystalline, have been presented over the past few years. In this paper, carrier-selective electron contacts featuring tunnel oxides are investigated by means of numerical device simulation. The influence of 1) the Si layer material, 2) the Si layer doping, 3) an additional in-diffusion in the absorber, 4) the surface recombination velocity at the oxide interface, and 5) the oxide thickness and the tunneling mass are investigated by means of an open-circuit voltage analysis, as well as a fill factor (FF) analysis. With the fundamental understanding generated in this paper, we are able to explain the excellent device performance of solar cells with carrier-selective contacts featuring tunnel oxides.