Air-Stable Flexible Photodetector Based on MXene-Cs₃Bi₂I₉ Microplate Schottky Junctions for Weak-Light Detection

Weak-light detection technology is widely used in various fields, including industry, high-energy physics, precision analysis, and reflection imaging. Metal-semiconductor-metal (MSM) photodetectors demonstrate high detectivity and high response speed and are one of the suitable structures for the preparation of weak-light detectors. However, traditional MSM photodetectors tend to exhibit high dark currents, which are not conducive to performance improvement. Here, a MXene-Cs₃Bi₂I₉-MXene weak-light detector is proposed. Based on the MXene-Cs₃Bi₂I₉ Schottky junctions, the dark current is reduced by 2 orders of magnitude and the responsivity is significantly improved compared with the traditional Cr/Au-Cs₃Bi₂I₉-Cr/Au MSM photodetector. The device demonstrates excellent photodetection capacity with a photoresponsivity of 6.45 A W^-1, a specific detectivity of 9.45 × 10¹¹ Jones, and a fast response speed of 0.27/2.32 ms. Especially, the device yielded a superior weak-light detectable limit of 10.66 nW cm^-2 and demonstrated excellent optical communication capability. Moreover, such a flexible device shows little degradation in photodetection performance after extreme bending for 4500 cycles, proving remarkable bending endurance and flexibility. The obtained results highlight the great potential of such Cs₃Bi₂I₉/MXene devices as a stable and environmentally friendly candidate for weak-light detection.