Interfacial Band Engineering in Solution-Processed CsPbBr3/Cs2AgBiBr6 Thin-Film Heterostructure for X-ray Detectors with High Sensitivity and Reduced Dark Current

Metal halide perovskites are promising materials for direct X-ray detection owing to their strong X-ray absorption, solution processability, and efficient charge separation and transport. However, thin-film perovskite detectors usually suffer from trap-assisted recombination and grain-boundary-limited charge transport, while single-crystal devices often show relatively high dark current. Herein, we report a solution-processed CsPbBr3/Cs2AgBiBr6 heterostructure thin-film X-ray detector with suppressed leakage current and improved charge extraction through interfacial band engineering. Structural, optical, and morphological analyses confirmed the formation of crystalline perovskite films with a well-defined CsPbBr3/Cs2AgBiBr6 interface. Under X-ray irradiation, the CsPbBr3/Cs2AgBiBr6 heterostructure device exhibited the photocurrent values of ∼4.57–9.52 nA over the dose rate of 120 to 600 µGy s–1. Although this photocurrent is lower than that of the single-crystal device, the hybrid detector exhibited better device performance with improved sensitivity and good signal-to-noise-relevant performance. The heterostructure thin film detector has achieved sensitivities of 171, 112, and 92 µC Gy–1 cm–2 at dose rates of 120, 240, and 360 µGy s–1, respectively. Based on the SNR = 3 detection criterion, the heterostructure exhibited the lowest detectable dose rate of 34.9 µGy s–1. These results demonstrate that CsPbBr3/Cs2AgBiBr6 heterostructure engineering provides a practical strategy for developing low-dark-current, high-sensitivity perovskite thin-film X-ray detectors.