Oriented Heterodimensional Perovskite Crystals for Self-Powered X-Ray Detection with Reduced Dark Current and Anisotropic Response

X-ray detectors utilizing 2D/3D heterodimensional perovskites have achieved great success. However, the labile nature of halide perovskites generally results in structures with random orientations and interfaces, which in turn increases the dark noise of X-ray detectors, hindering their use in low-dose X-ray detection. Here, it is shown that both anisotropy and ultralow dark current can be achieved in self-powered X-ray detectors using well-oriented 2D/3D heterodimensional perovskite crystals (HPCs). A halide diffusion-promoted welding approach is devised to create the oriented HPCs, enabling two distinct configurations: A lateral orientation where the inorganic frameworks of the two phases are perpendicular, and a vertical orientation with parallel inorganic slabs. The different crystalline orientations produce unique anisotropic X-ray detecting performance of 2D/3D HPCs, with a large anisotropic ratio of 4. Moreover, a self-powered X-ray detector using vertical HPC exhibits a greatly suppressed dark current density of 0.17 nA cm⁻² and a low detection limit of 77 nGy_air s⁻¹, enabling high-resolution X-ray imaging. In contrast, the lateral devices show higher X-ray sensitivity (1850 µC Gy_air⁻¹cm⁻²) at zero bias. This work reveals the interplay between crystalline orientation and X-ray detection performance, opening new possibilities for developing low-cost, low-noise X-ray detectors.