Centimeter‐Size Single Crystal of a Polar Dion–Jacobson Double Perovskite with Large Mobility‐Lifetime Product toward Effective X‐Ray Detection

Abstract Dion–Jacobson (DJ) double perovskites have emerged as environmentally friendly candidates for X‐ray detection, owing to their prominent optoelectronic performance and highlighted structural rigidity. Despite considerable efforts, the exploration of polar DJ‐type double perovskites for self‐powered X‐ray detection remains scarce. Herein, by introducing a diamine spacer to increase the structural rigidity, the study has successfully designed a new polar 2D DJ‐type double perovskite of (HIA) 2 AgBiBr 8 ( 1 , HIA = histamine), and centimeter‐size crystals are successfully obtained for effective X‐ray detection. Structurally, 1 features the quantum‐confined motif comprised of the directionally arranged inorganic perovskite sheets and alternating organic spacing cations, which endows a large mobility‐lifetime ( µτ ) product up to 1.23 × 10 −3 cm 2 V −1 on the par with typical X‐ray sensing candidates (MAPbI 3 wafers, µτ = 2 × 10 −3 cm 2 V −1 ). This attribute gives rise to a high sensitivity of 118 µCGy air −1 cm −2 to X‐ray illumination. Moreover, based on its polar structure, bulk photovoltaic effect with the photovoltage of ≈0.45 V is obtained in 1 , which affords the driving source toward the self‐powered X‐ray photodetection. This work highlights the potential of DJ‐type double perovskites in high‐energy ray detection and opens avenues for exploring new functionalities of DJ double perovskites as smart photoelectric candidates.