Inorganic Stable Sn-based Perovskite Film with Regulated Nucleation for Solar Cell Application
The tin (Sn)-based halide perovskite has attracted tremendous attentions as a lead-free alternative in halide perovskite solar cells (PSCs). Inorganic cesium tin triiodide (CsSnI3) provides a promising solution to the poor thermal stability of Sn-based halide perovskite. However, CsSnI3-based PSCs suffer from intrinsic defects such as the easy Sn2+/Sn4+ oxidation and the unbalanced rates between crystal nucleation and growth during film fabrication, leading to an inferior performance. Herein, the vacuum flash-assisted solution processing (VASP) method is utilized to fabricate the high-quality CsSnI3 film for the first time. Compared with CsSnI3 film fabricated with spin-coating route, the VASP CsSnI3 film shows an increased surface coverage, enhanced charge carrier mobility, improved film stability, and reduced background charge carrier density. These changes in turn facilitate the charge carrier transport and reduce the trap-assisted recombination in VASP PSCs. As a consequence, the VASP PSCs show greatly improved efficiency. Moreover, the VASP PSCs show a continuously increased efficiency as a function of storage time. After they are stored for 180 days, a PCE of 3.8% is achieved, which is also one of state-of-the-art performance for inorganic CsSnI3-based PSCs.