Real Sensitivity of Spin-Coated Lead Halide Perovskite Lateral X-ray Detectors

X-ray detectors are essential components in medical imaging and industrial inspection. However, current commercial direct X-ray detectors based on the electrical response of semiconductor materials like amorphous Si and Se show limited sensitivity below 100 μC Gy^-1 cm^-2 and relatively high production costs, restricting their utility, especially in medical applications that require minimal exposure to ionizing radiation. Recently, hybrid organic-inorganic perovskite halides (HOIPs) have emerged as promising materials for X-ray detection, offering advantageous properties such as high mobility-lifetime product, excellent X-ray attenuation, and the potential for low-cost, solution-based fabrication. Polycrystalline perovskites fabricated via spin coating offer a simpler and faster route, but the conventional spin coating method limits film thickness and, consequently, sensitivity. In this study, we address these limitations using a hot spin-coating technique to fabricate formamidinium lead halide (FAPbBr₂I) perovskite layers for lateral direct X-ray detectors on interdigitated electrodes. The enhanced method enables thicker films, improving X-ray attenuation and sensitivity. In addition, we also take into account the contributing effect of the ionization of the surrounding atmosphere, which has largely been ignored so far in the literature, resulting in overestimated sensitivity. The resulting FAPbBr₂I devices achieved a sensitivity of 988.7 ± 16.9 μC Gy^-1 cm^-2 if the air contribution is included and an outstanding real sensitivity of 206.7 ± 5.5 μC Gy^-1 cm^-2 after correcting for air ionization effects by a reference device. This true sensitivity exceeds that of many previously reported spin-coated devices and significantly surpasses the current commercial X-ray detectors, demonstrating its suitability for medical imaging and industrial nondestructive testing. Furthermore, this work shows the significant impact that air ionization can have on sensitivity measurements, especially in small-area devices, highlighting that air contribution is a factor that cannot be ignored for the proper characterization of direct X-ray detectors, laying the groundwork for future research on small-area spin-coated perovskite X-ray detectors.