Self‐Powered Ultraviolet‐Visible Photodetectors Based on Solution‐Processed 2D PEA ₂ PbBr ₄ /PEA ₂ PbI ₄ Heterostructures

Two-dimensional (2D) metal halide perovskites have great potential for applications in photodetectors (PDs), but there are still many challenges in the simple and efficient construction of their heterojunctions and the realization of excellent self-powered functions. In this work, we employ a simple ion exchange strategy to directly grow a 2D PEA₂PbI₄ layer on the PEA₂PbBr₄ film using a simple and easily implemented solution method. By precisely controlling the concentration of the phenethylamine hydroiodide/isopropanol (PEAI/IPA) solution, high-quality PEA₂PbBr₄/PEA₂PbI₄ heterojunction films are obtained. Furthermore, the self-powered PDs assembled based on the 2D/2D PEA₂PbBr₄/PEA₂PbI₄ heterojunction exhibit outstanding self-powered photoelectric performance across the UV-visible spectrum, with a responsivity of 75.6 mA/W and a detectivity of 4.16 × 10¹¹ Jones, respectively, which are more than five times that of the PEA₂PbBr₄ photodetector. In particular, this heterojunction photodetector exhibits excellent long-term self-powered photoelectric switching characteristics and environmental stability.