Interfacial engineering of ZnS passivating contacts for crystalline silicon solar cells achieving 20% efficiency

Despite the widespread use of metal oxides as electron selective contacts (ESCs) in dopant-free passivating contact crystalline silicon (c-Si) solar cells, their stability and performance improvements still encounter bottlenecks. Herein, we investigated the potential of zinc sulfide (ZnS) as ESC for n-type c-Si (n-Si) solar cells. The performance of the ZnS-based dopant-free n-Si solar cells has been optimized by deploying the low-work-function Mg/Ag stack electrode and a SiOx passivation interlayer with forming gas annealing (FGA) treatment. An efficiency of 20.03% has been achieved for n-Si solar cells with SiOx(FGA)/ZnS/Mg/Ag contact, which is so far the highest efficiency reported for ZnS-based c-Si solar cells. Moreover, the device maintained ≥98% of its initial efficiency after being stored in the air for 30 days, indicating the promise of long-term deployment. Our work highlights the great potential of using metal sulfides as high-performance and stable passivating contacts in dopant-free c-Si solar cells.