High‐Performance Self‐Driven MAPbI₃‐MAPbBr₃ Perovskite Single Crystal Heterojunction Photodetectors for Ultra‐Sensitive Weak Light Imaging

Abstract The rapid advancement of optoelectronic devices, particularly photodetectors, demands enhanced sensitivity for detecting weak light. In this study, MAPbI 3 ‐MAPbBr 3 perovskite single crystal heterojunctions (SCHs) are fabricated via atomic force bonding using liquid‐phase epitaxy, with polydimethylsiloxane (PDMS) serving as a substrate protector. The resulting SCHs photodetector exhibits self‐driven operation, an ultra‐low dark current, and a high on‐off ratio of 5.8 × 10 4 at 0 V bias. Under weak illumination and 5 V bias, the device achieves a maximum external quantum efficiency of 414.9%. With a remarkable detection rate of 4.5 × 10 13 Jones, the device demonstrates outstanding potential for weak light imaging. Furthermore, the self‐driven SCHs photodetector enables high‐quality imaging under a 445 nm light source at a remarkably low intensity of 2.7 µW cm −2 , without the need for any external power supply.