Homogeneous Bridging Induces Compact and Scalable Perovskite Thick Films for X‐Ray Flat‐Panel Detectors

Abstract Solution‐processed organic–inorganic hybrid perovskite polycrystalline thick films have shown great potential in X‐ray detection. However, the preparation of compact perovskite thick films with large area is still challenging due to the limitation of feasible ink formulation and pinholes caused by solvent volatilization. Post‐treatment and hot‐pressing are usually involved to improve the film quality, which is however unsuitable for subsequent integration. In this work, a homogeneous bridging strategy is developed to prepare compact perovskite films directly. A stable perovskite slurry with suitable viscosity consisting of undissolved grains and supersaturated solution is formed by adding a weak coordination solvent to the pre‐synthesized microcrystalline powders. Small perovskite grains in situ grow from the saturated solution during the annealing, filling the pinholes and connecting the surrounding original grains. As a result, large‐area perovskite thick film with tight grain arrangement and ultralow current drift is blade‐coated to achieve X‐ray imaging. The optimal device displays an impressive mobility‐lifetime product of 2.2 × 10 −3 cm 2 V −1 and a champion ratio of sensitivity to the dark current density of 2.23 × 10 11 µC Gy air −1 A −1 . This work provides a simple and effective route to prepare high‐quality perovskite thick films, which is instructive for the development of perovskite‐based X‐ray flat‐panel detectors.