3D Lead‐Free Double Perovskite via Anchoring A‐Site Cation for Ultralow Dose and Stable X‐Ray Detection

Abstract 3D lead‐free hybrid double perovskites exhibit remarkable potential for direct X‐ray detection owing to their strong photon attenuation capabilities, efficient charge mobility, and low‐cost fabrication. However, the development of new 3D double perovskites based on large organic cations remains challenging due to the Goldschmidt tolerance factor constraint, which impedes further exploration of their potential in radiation detection. Herein, a new 3D lead‐free double perovskite (Mor) 2 RbSbI 6 ( 1 , Mor = morpholinium) is synthesized, featuring the dense perovskite framework anchored by A‐site cations. The high‐quality single crystals of 1 present a high mobility‐lifetime product (1.52 × 10 −3 cm 2 V −1 ) and low dark current drift, enabling it to achieve simultaneously a high sensitivity (1.09 × 10 4 µC Gy air −1 cm −2 ) and an ultralow detection limit (3.1 nGy air s −1 ) under identical operating voltage. Meanwhile, the A‐site cation anchoring strategy prevents ion migration‐induced structural collapse during X‐ray detection, thereby improving its radiation hardness and operating stability. These findings provide crystal structural insights to design new types of perovskite materials for “green” and high‐performance radiation detectors.