High performance X-ray detector based on 3-layered parallel FAPbBr₃ single crystal film

X-ray detection is widely applied in medical imaging, security screening, industrial non-destructive testing, astrophysics, and nuclear radiation monitoring. Metal halide perovskites have shown tremendous potential in this field due to their excellent optoelectronic properties. Attracted by the superior crystal quality of single-crystal materials, various perovskite single crystals have been extensively explored for X-ray detection. However, despite their high crystallinity, the considerable thickness of bulk single crystals limits the efficient collection of photogenerated carriers, leaving room for performance improvement in single-crystal-based X-ray detectors. Perovskite single-crystal films (SCFs), characterized by their much smaller thickness in the vertical direction compared to lateral dimensions, can significantly shorten the carrier transport path. Compared to bulk single crystals with thicknesses ranging from millimeters to centimeters, SCFs with thicknesses of hundreds of nanometers to hundreds of micrometers are more favorable for carrier transport. However, the reduced thickness also limits their ability to absorb X-ray, restricting the X-ray response. Achieving both efficient carrier collection and strong X-ray absorption remains a key challenge in the structural design of perovskite X-ray detectors. In this study, we fabricated high-quality FAPbBr3 single-crystal films with a thickness of approximately 212 μm using a local heating and spatial confinement method. To overcome the trade-off between absorption and response speed, we constructed a 3-layered parallel architecture (Au/FAPbBr3/Au/FAPbBr3/Au/FAPbBr3/ITO) for fast-response and high-sensitivity X-ray detection. In this structure, each single-crystal film layer is individually connected to the top and bottom electrodes, allowing efficient generation and collection of photogenerated carriers without increasing the overall carrier drift distance. This design synergistically combines the benefits of enhanced X-ray absorption, fast response, and high sensitivity. Compared to a single-layer FAPbBr3 SCF device, the 3-layered parallel structure provides greater overall thickness and higher X-ray absorption efficiency while maintaining efficient charge extraction. In contrast to bulk FAPbBr3 single crystals, where carrier drift is limited by the theoretical drift length μτE (μ: mobility, τ: lifetime, E: electric field), excessive thickness (d > μτE) leads to severe carrier recombination and poor charge collection. Increasing the electric field will result in higher dark current and noise, while improving the μτ product through doping or structural modification yields limited enhancement. In the 3-layered SCF device, carriers drift within each individual layer (~212 μm), which is significantly shorter than in bulk crystals (~3 mm), effectively reducing recombination and improving response speed, even under low bias. Moreover, the FAPbBr3 material exhibits intrinsically low dark current and suppressed drift compared to MA+ and Cs+-based perovskites, contributing to better device stability and lower noise. Experimental results showed that the 3-layered parallel structure device improved the detection efficiency of the detector, with a sensitivity of 4773 μC Gy−1 cm−2 for 30 keV X-rays under a 10 V bias, which was 1.54 times higher than that of the single-layer single-crystal film (1879 μC Gy−1 cm−2). Additionally, the 3-layered parallel device exhibited a rapid response time of 108/188 μs, which was only 1/5 of that observed in bulk single-crystal devices (596/1.03 ms), providing an innovative solution for realizing high-performance X-ray detection.