Kinetic‐Controlled Perovskite Surface Smoothing to the Pixel‐Level Uniformity for High‐Resolution X‐Ray Flat‐Panel Imaging

Perovskite X‐ray flat‐panel detectors (FPDs) show great potential for the next‐generation high‐resolution imaging. However, the non‐uniformity of perovskite films across multi‐pixels remains a critical challenge, severely limiting the spatial resolution and signal‐to‐noise ratio of FPDs. To tackle this problem, a kinetic‐controlled surface smoothing strategy is introduced that exploits solvent‐induced surface dissolution, leveling, and evaporative recrystallization with high delicacy. This method simultaneously smooths the surface and heals surface defects, resulting in a highly uniform film with markedly reduced Pb‐rich intermediate phase segregation. The optimized perovskite detector exhibits high pixel‑level uniformity, ultra‐low fixed pattern noise (2.73%), and high sensitivity (86150 µC Gy air −1 cm −2 ). Moreover, the detector achieves a record spatial resolution of 0.54 lp pix −1 , outperforming commercial α‐Se detectors and placing it among the top performers of the kind reported to date. Notably, the surface smoothing process is simple, cost‐effective, and readily scalable to large‐area arrays, providing a general and practicable strategy for high‐performance X‐ray imaging applications.