Rigid Bis-Amidinium Anchoring Engineering Enables Synergistic Defect Suppression and Ion Stabilization for High-Performance Flexible Perovskite X-Ray Detectors and TFT-Array Imaging.

Abstract

Flexible direct-conversion X-ray detectors based on halide perovskites hold great promise for mechanically compliant and array-integrated imaging, yet their performance is limited by grain-boundary defects and electrical instability in polycrystalline thick films. Here, we introduce 1,4-benzenedicarboximidamide dihydrochloride (p-BDAm) as an additive for regulating polycrystalline methylammonium lead iodide (MAPbI3) detector layers. Spectroscopic measurements and density functional theory (DFT) calculations support multisite interactions between the bis-amidinium framework and Pb-I-containing species as a plausible contribution to the p-BDAm-mediated regulation of the local grain-boundary environment and crystallization behavior. Overall, p-BDAm incorporation suppresses nonradiative recombination, increases the resistivity and mobility-lifetime product, raises the apparent activation energy extracted from temperature-dependent conductivity from 0.17 to 0.49 eV, and substantially improves dark-current stability. The optimized flexible perovskite composite membrane detector achieves a sensitivity of 2165.5 µC Gyair -1 cm-2 at 10 V and an estimated detection limit of 15.0 nGyair s-1. Moreover, the p-BDAm-regulated MAPbI3 layer is compatible with thin-film transistor (TFT)-array integration, enabling parallel X-ray imaging. A representative TFT image was obtained at an X-ray dose rate of 12.3 µGyair s-1 with an exposure time of 0.5 s. These results demonstrate a transferable molecular-regulation strategy for stabilizing polycrystalline perovskite X-ray detectors across flexible and array-integrated architectures.

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