Halogen‐Mixed 1D CsPbIBr₂ Photodetectors for Enhanced Ultraweak Light Detection

Abstract Metal halide perovskites recently have emerged as a promising candidate for photodetection due to their exceptional photoelectric performance. However, the high dark current in these materials has hindered their practical application to imaging. In this study, a novel halogen‐mixed CsPbIBr₂ microwire photodetector that has a remarkable reduction of dark current by over 100‐fold (compared to CsPbBr₃), along with a substantial increase in photocurrent, which yields a significantly improved on/off ratio of 6.56 × 10⁴, is developed. More importantly, the halogen‐mixed perovskite photodetector exhibits enhanced photodetection performance, including a high responsivity of 133 A W⁻¹ and a remarkable specific detectivity of 4.02 × 10¹² Jones even under ultraweak light conditions as low as 4.5 nW cm⁻². More specifically, high‐resolution images are successfully obtained under ultraweak light conditions. The combined analysis of experimental results and first‐principles calculation attribute the excellent performance of the CsPbIBr₂ microwire photodetector to a significant reduction in dark current by suppressing ion migration and increasing carrier effective mass, and a remarkable increase in photocurrent resulting from reduced bandgap and enhanced light absorption, as compared to CsPbBr₃. This research represents a significant advancement in the development of high‐performance 1D perovskite‐based photodetectors, with promising implications for ultra‐weak light imaging applications.