Approaching 23% efficient n-type crystalline silicon solar cells with a silicon oxide-based highly transparent passivating contact

The concept of passivating contacts is indispensable for realizing high-efficiency crystalline silicon (c-Si)-based solar cells, and its implementation and integration into production lines has become an essential research subject. A desirable transparent passivating contact should theoretically combine excellent electrical conductivity, distinguished surface passivation and high optical transparency. However, it is challenging to simultaneously achieve the optimization of all three requirements. Here, the application potential of the phosphorous-doped polycrystalline silicon-oxide (n-poly-SiOx) as an efficient hole-selective contact in tunnel oxide passivated contact (TOPCon) solar cells is highlighted. The oxygen content can be regulated by the carbon dioxide (CO2) gas flow during the plasma enhanced chemical vapor deposition (PECVD) process, and the optimal doping concentration is determined. While the wide band gap of n-poly-SiOx enables ideal optical performance, it also ensures excellent passivation and high conductivity, which eventually translates into an optimized short-circuit current density (41.53 mA/cm2), fill factor (79.21%), open-circuit voltage (687.8 mV) and efficiency of 22.62% for the proof-of-concept TOPCon solar cell. Additionally, this contact with the incorporation of oxygen elements can suppress the formation of hydrogen-induced blisters, which critically degrades passivation. Our work highlights a promising strategy to improve the performance of TOPCon solar cells by employing n-poly-SiOx based transparent passivating contact, and its passivation mechanism and working principle are also investigated.