X-rays have extensive applications across multiple fields, including medical imaging, security screening, container inspection, defect detection, pollution detection, and quality control in the material industry. Halide perovskite single crystals have emerged as promising materials due to their high X-ray absorption coefficient, substantial carrier mobility-lifetime product, tunable bandgap, high resistivity, and cost-effective synthesis methods. These perovskite single-crystal materials demonstrate successful implementation in X-ray detectors and show potential as next-generation ionizing radiation semiconductor materials. Cesium lead bromide (CsPbBr₃) single crystals present a viable option for large-scale commercial X-ray detection applications. However, ion migration negatively impacts the long-term stability and optoelectronic properties of three-dimensional perovskite CsPbBr₃ single crystal X-ray detectors. PEABr, a typical component of long-chain organic cations in two-dimensional perovskite, forms two-dimensional perovskite benzylamine lead bromide (PEA₂PbBr₄). The phenylethylammonium ion (PEA⁺) organic layer between the octahedral layers of lead bromide exhibits high resistivity and hydrophobicity, resulting in enhanced stability and high ion activation energy. Consequently, low-dimensional perovskite materials demonstrate superior ion migration inhibition compared to three-dimensional perovskite. Additionally, bromo perovskite materials grown in halogen-rich environments, such as hydrobromid (HBr), exhibit improved crystal quality. This study investigated the growth of two-dimensional perovskite microcrystals on CsPbBr₃ single crystal surfaces using PEA₂PbBr₄ solutions with varying HBr concentrations. The research examined surface morphology changes under different passivation conditions and analyzed the performance variations of CsPbBr₃ single crystal X-ray detectors before and after passivation. The study compared detector performance for different treatment methods and demonstrated the effectiveness of passivation in enhancing X-ray detection capabilities, potentially advancing the commercialization of perovskite single crystal X-ray detectors.

CsPbBr₃ single crystal ingots were prepared using the Bridgman method, followed by cutting and polishing to obtain CsPbBr₃ single crystals. The crystals underwent treatment in HBr solutions containing varying concentrations of two-dimensional perovskite PEABr can form two-dimensional perovskite benzylamine lead bromide (PEA₂PbBr₄) for microcrystal growth. Following passivation, titanium (Ti) metal electrodes were deposited on the top and bottom surfaces to fabricate X-ray detectors. Characterization methods included X-ray diffraction (XRD) for phase analysis, photoluminescence (PL) measurements using a 405 nm wavelength laser, and scanning electron microscope (SEM) analysis for surface morphology examination. X-ray irradiation utilized an Amptek Mini X2 X-ray tube (Ag target) at 30 kV voltage, with dose control through tube current adjustment. Voltage-current measurements were conducted using a Keithley 2634B source meter within a 3 mm thick lead-shielded box. The experimental setup incorporated a programmable motion platform positioning an aluminum (Al) plate between the X-ray tube and detector, enabling two-dimensional image generation through photocurrent variations corresponding to X-ray dose changes through aluminum gaps.

XRD analysis and PL spectra confirm the formation of two-dimensional perovskite PEA₂PbBr₄ microcrystals on the CsPbBr₃ single crystal surface (Fig. 2). The CsPbBr₃ single crystal surface, passivated with a 0.01 mol/L PEA₂PbBr₄ acid solution, exhibits minimal surface scratches from cutting and polishing, without large-scale two-dimensional microcrystal formation due to excess concentration (Fig. 4). Following deposition and device fabrication, the CsPbBr₃ single crystal detector maintains a low dark current of approximately 10 nA and a hysteresis width below 1 nA under a 200 V bias voltage (Fig. 6). Under varying X-ray dose exposures, the CsPbBr₃ single crystal detector maintains stable dark current and demonstrates superior resolution at low X-ray dose rates (Fig. 7). Data analysis reveals that the CsPbBr₃ single crystal detector exhibits high sensitivity and low X-ray detection threshold (Fig. 8). Comparative analysis with CsPbBr₃ single crystal detectors treated through alternative methods indicates that the acid solution-based two-dimensional perovskite passivation method substantially improves X-ray detection performance (Table 1). In imaging mode, the CsPbBr₃ single crystal detector produces distinct mask pattern images at a low dose rate of 200 nGy·s^-1 (Fig. 10).

This research successfully demonstrates the passivation of CsPbBr₃ single crystals with microcrystals using PEA₂PbBr₄ in HBr solution, effectively suppressing ion migration within the single crystal detectors. The findings indicate that CsPbBr₃ single crystal detectors passivated at 0.01 mol/L concentration demonstrate optimal passivation performance. The detector achieves superior sensitivity of 9.55×10⁴ μC·Gy^-1·cm^-2, and a minimal dose level of 13.8 nGy·s^-1. Additionally, the detector enables X-ray imaging with 1 mm² spatial resolution at a low X-ray dose rate of 200 nGy·s^-1. These results establish that growing two-dimensional perovskite microcrystals on three-dimensional perovskite single crystals through passivation significantly enhances optoelectronic detector performance, offering valuable passivation strategies and design guidance for three-dimensional perovskite detectors.