Metal chalcogenide electron extraction layers for nip-type tin-based perovskite solar cells

Tin-based perovskite solar cells have garnered attention for their biocompatibility, narrow bandgap, and long thermal carrier lifetime. However, nip-type tin-based perovskite solar cells have underperformed largely due to the indiscriminate use of metal oxide electron transport layers originally designed for nip-type lead-based perovskite solar cells. Here, we reveal that this underperformance is caused by oxygen vacancies and deeper energy levels in metal oxide. To address these issues, we propose a metal chalcogenide electron transport layer, specifically Sn(S_0.92Se_0.08)₂, which circumvents the oxygen molecules desorption and impedes the Sn²⁺ oxidation. As a result, tin-based perovskite solar cells with Sn(S_0.92Se_0.08)₂ demonstrate a V_OC increase from 0.48 - 0.73 V and a power conversion efficiency boost from 6.98 - 11.78%. Additionally, these cells exhibit improved stability, retaining over 95% of their initial efficiency after 1632 h. Our findings showcase metal chalcogenides as promising candidates for future nip-type tin-based perovskite solar cell applications.