Highly Efficient Surface Passivation with Cation-Exchanged Quasi-2D Perovskites for High-Sensitivity and Low-Dose X-ray Flat-Panel Imaging

Perovskite-based X-ray flat-panel detectors (FPDs) are promising candidates for next-generation low-dose and high-resolution imaging. However, their performance is significantly limited by severe interfacial defects in polycrystalline thick films, which induce nonradiative recombination, elevate dark current, degrade sensitivity, and collapse contrast-to-noise ratio (CNR). Herein, we develop a universal cation-exchange strategy via sequential thermal evaporation and a liquid-phase reaction (STELR) to construct a conformal quasi-2D perovskite passivation layer on the surface of 3D perovskites. This approach reduces surface trap density by nearly an order of magnitude and suppresses noise current density to 6 × 10^-14A Hz^-1/2. Consequently, the passivated detector achieves a sensitivity of 59,040 μC Gy_air^-1 cm^-2 and a detection limit of 18.6 nGy_air s^-1, enabling FPDs with a superior spatial resolution of 0.71 lp/pixel. Furthermore, the passivated devices maintained high-quality X-ray imaging (CNR = 2.09) at an ultralow dose of 29.9 μGy_air, demonstrating significant potential for advancing clinical and industrial-grade low-dose imaging systems.