Solution‐Grown Hypervalent CsI 3 Crystal for High‐Sensitive X‐Ray Detection

Herein, a novel binary compound hypervalent CsI 3 crystal is designed for X‐ray detection. Solution‐grown rod‐like CsI 3 single crystal is identified as a semiconductor with a bandgap of 1.79 eV and high resistivity of 2.17 × 10 9  Ω cm, which make it suitable for X‐ray detection. Based on carbon/CsI 3 crystal/carbon device, a high X‐ray sensitivity of up to 158.1 ± 6.0 μC Gy −1  cm −2 is achieved under a low electrical field of 55 V mm −1 , which is eight times higher than that of the commercial α‐Se X‐ray detectors. The high sensitivity of hypervalent CsI 3 is attributed to the long carrier life time (≈470 μs) and large photocurrent gain (150%). The potential applications of photoconversion and nuclear radiation detection using alkali halides are demonstrated.