Near-infrared photodetection in tin halide perovskites via compositional engineering

Abstract

Tin (Sn) halide perovskites, with an optical bandgap below 1.4 eV, are promising for near-infrared photodetectors (NIR-PDs). However, their inherent instability due to Sn2+ oxidation and sensitivity to processing often results in non-uniform films with low crystallinity. Most research has focused on formamidinium tin triiodide (FASnI3), while methylammonium tin triiodide (MASnI3), with an optical bandgap of 1.2–1.3 eV and light absorption in the 300–1100 nm range, has been less explored due to its instability. Here, we demonstrate that substituting A-site cations (Cs and Rb) and X-site halides (Cl) in MASnI3 significantly enhances its stability, improving crystallinity and reducing trap density. PD devices with modified MASnI3 exhibit enhanced photo-response across the visible to NIR region, achieving specific detectivity over 1.7 × 1012 Jones at 940 nm, with a fast response time (trise/tfall = 3.85 μs/5.70 μs) under low irradiance of 0.104 mW cm−2.