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

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 Sn²⁺ is easily oxidized to Sn⁴⁺. 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 PEA₂SnI₄ films with tin fluoride (SnF₂) additive are prepared in air using a nitrogen quenching hot casting method. The photodetectors with an optimal SnF₂ concentration of 20% exhibit a fast response speed of 0.56 ms and an excellent specific detectivity of 6.32 × 10¹³ Jones, the best combination of THP-based photodetectors reported hitherto. The SnF₂ additive is found to suppress the formation of Sn vacancies and improve the crystallinity of PEA₂SnI₄ films. The work provides an air-processing technology of Pb-free perovskite, which is easy to commercialize, and SnF₂ additive engineering offering an effective way to demonstrate high performance photodetectors and image recognition applications.