Robust Perovskite X‐ray Flat Panel Detector via Large‐Grain Interpenetrating Crystals and Lateral Grain Boundary Anchoring

Abstract Polycrystalline organic‐inorganic metal halide perovskite films present significant potential for use in next‐generation X‐ray flat‐panel imagers (FPXI) due to their low‐cost, large‐area fabrication capabilities. However, achieving high‐performing FPXI necessitates thick films (>300 µm) with high‐quality, large‐size polycrystalline perovskite grains. Perovskite thick films are often found to suffer from insufficient grain packing density, leading to structural defects such as pores, fractures, and delamination, thereby reducing device yield and increasing dead pixel rates. Herein, a polymer‐assisted in situ growth strategy is proposed that successfully produces large grains up to 360 µm with reinforced grain boundaries, the largest among all the reported perovskite thick films. The resultant compact MAPbI ₃ thick films simultaneously achieve record mechanical properties (Young´s modulus of 11.14 GPa) and electrical performance (µτ product of 2.14 × 10 ⁻³ cm ² V ⁻¹ ). The corresponding FPXI displays a high spatial resolution of 5.27 lp mm ⁻¹ and an ultralow dead pixel rate of 0.832%. Moreover, the thick film demonstrates strong adhesion to the substrate, remaining firmly attached even under a tensile force of 500 g. This work not only contributes an effective fabrication strategy for high‐performance FPXI, but also provides a universal solution to the enduring mechanical stability challenges in perovskite optoelectronics.