Identifying Carrier Behavior in Ultrathin Indirect‐Bandgap CsPbX₃ Nanocrystal Films for Use in UV/Visible‐Blind High‐Energy Detectors

Abstract

Abstract High‐energy radiation detectors such as X‐ray detectors with low light photoresponse characteristics are used for several applications including, space, medical, and military devices. Here, an indirect bandgap inorganic perovskite‐based X‐ray detector is reported. The indirect bandgap nature of perovskite materials is revealed through optical characterizations, time‐resolved photoluminescence (TRPL), and theoretical simulations, demonstrating that the differences in temperature‐dependent carrier lifetime related to CsPbX 3 (X = Br, I) perovskite composition are due to the changes in the bandgap structure. TRPL, theoretical analyses, and X‐ray radiation measurements reveal that the high response of the UV/visible‐blind yellow‐phase CsPbI 3 under high‐energy X‐ray exposure is attributed to the nature of the indirect bandgap structure of CsPbX 3 . The yellow‐phase CsPbI 3 ‐based X‐ray detector achieves a relatively high sensitivity of 83.6 μCGy air −1 cm −2 (under 1.7 mGy air s −1 at an electron field of 0.17 V μm −1 used for medical diagnostics) although the active layer is based solely on an ultrathin (≈6.6 μm) CsPbI 3 nanocrystal film, exceeding the values obtained for commercial X‐ray detectors, and further confirming good material quality. This CsPbX 3 X‐ray detector is sufficient for cost‐effective device miniaturization based on a simple design.