Organic-inorganic hybrid perovskite wafers have demonstrated significant potential for large-area X-ray detection applications. However, current perovskite wafers exhibit poor optical transparency and suboptimal crystal quality, which severely limit the performance and stability of X-ray detectors. Self-powered perovskite X-ray detectors have attracted increasing attention due to their advantages of low power consumption, portability, and excellent adaptability.

This study aims to develop high-performance self-powered X-ray detectors by fabricating transparent MAPbBr₃/MAPbCl₃ heterojunction wafers through hot-pressing technology, and investigate their self-driven detection mechanisms.

Firstly, MAPbBr₃ and MAPbCl₃ single crystals were grown using the improved inverse temperature crystallization (ITC) method and subsequently grounded into uniform powders with average particle sizes of 0.38 μm and 0.57 μm, respectively. Then, a gradient temperature-controlled bidirectional hot-pressing process was developed, where the powders were placed on opposite sides of a cylindrical mold and subjected to crystallization-induced pressing at 297 MPa while gradually heating from 25 °C to 60 °C for 10 h. Finally, comprehensive characterization techniques including X-ray diffractometer (XRD), scanning electron microscope (SEM), ultraviolet visible (UV-vis) spectroscopy, and ultraviolet photoelectron spectroscopy (UPS) were employed to analyze the crystal structure, morphology, optical properties, and energy band alignment of the fabricated heterojunction wafers.

The hot-pressing technique successfully produces MAPbBr₃/MAPbCl₃ heterojunction wafers with excellent optical transparency and clear interfaces. The Au-MAPbBr₃/MAPbCl₃-Au structured X-ray detector exhibits a sensitivity of 782.26 μC·Gy_air^-1·cm^-2 and an ultra-low detection limit of 57 nGy_air·s^-1 at 0 V bias, representing superior performance compared to single-component detectors. Under 10 V bias, the sensitivity further increases to 7 785.32 μC·Gy_air^-1·cm^-2, which is 4.33 and 6.09 times higher than MAPbBr₃ and MAPbCl₃ wafer detectors, respectively. The device maintains stable performance after cumulative absorption of 3 675 μGy_air of X-ray radiation.

The enhanced performance of the heterojunction X-ray detectors is primarily attributed to the built-in electric field formed by the PN heterojunction, which effectively suppresses dark-state carrier recombination and enhances carrier transport under X-ray irradiation. The advancement achieved in this study significantly expands the potential of perovskite-based detectors for low-power, large-area detection applications and provides a new direction for developing high-performance self-powered X-ray detection technology.