Controllable Perovskite Single Crystal Heterojunction for Stable Self‐Powered Photo‐Imaging and X‐Ray Detection

Abstract Semiconductor heterostructures underpin the design and performance of virtually all modern optoelectronic systems. The clear interface, high crystalline quality, and suitable energy band match lay the foundation for high‐performance heterojunction optoelectronic devices. Here, a facile solution epitaxial growth method is demonstrated for controllably growing CH 3 NH 3 PbBr 3 single crystal (SC) on the CH 3 NH 3 PbCl 3 SC, which forms a pn heterojunction with a well‐defined interface and high single‐crystalline quality. The thickness of the epitaxial layer can be finely controlled by adjusting the growth time. Benefiting from excellent built‐in electrical potential at pn heterojunction, the heterojunction detector shows an obvious rectification behavior and high performance in photo‐imaging and X‐ray detection without any power supply, including high responsivity (26.8 mA W −1 ), fast response time (8/613 µs), and high sensitivity of 868 µC Gy air −1 cm −2 with a record lowest detectable X‐ray dose rate of 15.5 nGy air s −1 . Furthermore, it exhibits high‐fidelity UV photo‐imaging capability at zero bias voltage. In addition, the heterojunction detector shows excellent stability by maintaining 99% of the initial responsivity after 120 days without any encapsulation in the atmosphere. This work enables a significant advance in engineering perovskite SC heterojunction for developing novel and functional devices.