Carboxyl-Group-Anchored Structural Polarity in a Layered Metal Halide for High-Performance Self-Powered X-ray Detection

Abstract

Polar metal halide perovskites that exhibit the bulk photovoltaic effect (BPVE) are promising candidates for self-powered X-ray detection because they can generate photoresponses at zero bias. However, typical interlayer noncovalent interactions often suffer from limited directionality and weak anchoring capability, which hinders the simultaneous construction of polar structures and enhancement of lattice stability. Herein, we develop a carboxyl-substitution strategy to construct a polar two-dimensional (8-AOC) 2 PbBr 4 (8-AOC = 8-aminocaprylic acid) perovskite, thereby achieving efficient and durable self-powered X-ray detection. Carboxyl substitution is accompanied by inorganic-framework distortion within the polar P2 1 space group and by a cross-linked interlayer hydrogen-bonding network that inhibits ion migration. Consequently, the detector achieves a high sensitivity of 128.08 μC Gy -1 cm -2 and a LoD of 98.8 nGy s -1 at zero bias, approximately 1/56 of the conventional medical diagnostic dose rate threshold (5.5 μGy s -1 ). Notably, the device retains 95.9% of its initial sensitivity after 30 days of ambient storage and delivers stable responses during repeated X-ray irradiation, demonstrating strong storage and irradiation-cycling stability. This work presents carboxyl-group functionalization as a strategy for combining polar-structure design with interlayer hydrogen-bond stabilization in self-powered X-ray detectors.