Fabrication and Performance Optimization of CsPbBr ₃ /SrTiO ₃ Single‐Crystal Heterojunction Photodetectors for Optical Communication Systems

Abstract Due to their excellent photoelectric activity, material stability, and low lattice mismatch, halide perovskite CsPbBr 3 and oxide perovskite SrTiO 3 are ideal candidates for constructing heterojunction photodetector diodes. However, the realization of such all‐single‐crystal, high‐performance heterojunctions remains challenging. Herein, an all‐single‐crystal CsPbBr 3 /SrTiO 3 heterojunction is successfully fabricated at low temperatures based on a surface reconstruction method. The effects of Nd doping and graphene electrodes on the optoelectronic properties of the device are investigated. Benefiting from the excellent heterojunction structure, enhanced built‐in electric field, and van der Waals contact, the device exhibits significantly improved rectification characteristics, photoresponsivity, and light‐to‐dark ratio. The CsPbBr 3 /Nb:SrTiO 3 /Graphene device achieves a responsivity of up to 1.1 mA W −1 and a response time of only 0.29 µs under 0 V bias. By integrating the device into an optical communication system using embedded technology, byte transmission is successfully realized, demonstrating the practical application potential of single‐crystal devices as signal receivers in optical communication systems.