Fast and Highly Sensitive Photodetectors Based on Pb‐Free Sn‐Based Perovskite with Additive Engineering

Abstract Organic–inorganic halide perovskites have been widely investigated for the fabrication of photodetectors because of their excellent optoelectronic properties. However, the toxicity of Pb‐based perovskites and the lack of manufacturing technology in air limits the commercialization of perovskite‐based photodetectors. Tin halide perovskite (THP) is a promising candidate to replace Pb‐based perovskites due to its low toxicity and potential commercialization. However, THP suffers poor stability in air because Sn 2+ is easily oxidized to Sn 4+ . This “self‐doping” effect not only degrades device performance rapidly, but also makes it difficult to fabricate THP‐based devices in air. Here, Pb‐free Sn‐based 2D perovskite PEA 2 SnI 4 films with tin fluoride (SnF 2 ) additive are prepared in air using a nitrogen quenching hot casting method. The photodetectors with an optimal SnF 2 concentration of 20% exhibit a fast response speed of 0.56 ms and an excellent specific detectivity of 6.32 × 10 13 Jones, the best combination of THP‐based photodetectors reported hitherto. The SnF 2 additive is found to suppress the formation of Sn vacancies and improve the crystallinity of PEA 2 SnI 4 films. The work provides an air‐processing technology of Pb‐free perovskite, which is easy to commercialize, and SnF 2 additive engineering offering an effective way to demonstrate high performance photodetectors and image recognition applications.