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

Abstract Intrinsic near‐infrared response of silicon‐based photodetectors can cause undesirable noise and thus undermine performance in visible‐light applications. All‐inorganic perovskite CsPbI x Br 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 x Br 3–x is an effective way to simultaneously address stability and defect challenges. Herein, a facile and universal strategy is demonstrated to construct 2D PEA 2 PbI 2 Br 2 /quasi‐2D PEA 2 CsPb 2 I 5 Br 2 /3D CsPbI x Br 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 x Br 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 × 10 12 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 x Br 3–x heterostructures and stimulates infrared‐blind visible‐light applications.