High-performance SiO_x/MgO_x electron-selective contacts for crystalline silicon solar cells

High carrier recombination loss at the metal and silicon contact regions is one of the dominant factors constraining the power conversion efficiency (PCE) of crystalline silicon (c-Si) solar cells. Metal compound-based carrier-selective contacts are being intensively developed to address this issue. In this work, we present a high-performance electron-selective SiO_x/MgO_x contact for c-Si solar cells. The SiO_x/MgO_x stack is prepared by thermally-grown SiO_x (∼0.7 nm) and thermally-evaporated MgO_x (∼1.0 nm). The electron selectivity of SiO_x/MgO_x contact is investigated by measuring the surface passivation and the contact resistivity (ρ_c) on the c-Si surface. The results demonstrate that optimized SiO_x/MgO_x contact displays a very low ρ_c (3.4 mΩ cm²) and a good surface passivation on an n-type c-Si surface simultaneously. A high PCE of 21.1% is achieved on an n-type c-Si solar cell featuring a full-area SiO_x/MgO_x rear contact.