2D/Quasi-2D/3D CsPbIxBr3–x Vertical Heterostructures for High-Performance Infrared-Blind Visible-Light Photodetectors Toward Imaging Application

Intrinsic near-infrared response of silicon-based photodetectors can cause undesirable noise and thus undermine performance in visible-light applications. All-inorganic perovskite CsPbI_xBr_3–x with the absorption cutoff at ≈720 nm shows significant potential in visible-light photodetection. However, its poor phase stability and high defect density on surfaces of polycrystalline films significantly impairs its performance. Constructing low-dimension/3D heterostructure atop CsPbI_xBr_3–x is an effective way to simultaneously address stability and defect challenges. Herein, a facile and universal strategy is demonstrated to construct 2D PEA₂PbI₂Br₂/quasi-2D PEA₂CsPb₂I₅Br₂/3D CsPbI_xBr_3–x heterostructures by two-step sequential surface treatment with phenylethylammonium bromide (PEABr). The PEABr pre-treatment in the first step favors the volatilization of dimethylammonium iodide to produce higher phase stability. With the addition of strong-polarity methanol in the solution for the second treatment, PEABr can easily react with the PbI_xBr_2–x rich surface to form low-dimensional/3D perovskites heterostructure. Resultant heterostructure-based photodetectors achieve superior performance in photodiode-type photodetectors and enhanced stability, specifically a champion external quantum efficiency of 84% and detectivity of 3.1 × 10¹² Jones at 690 nm, and linear dynamic range of 163 dB. Finally, the visible-light imaging is demonstrated. This work offers a universal approach to realize CsPbI_xBr_3–x heterostructures and stimulates infrared-blind visible-light applications.