Green Chiral‐Polar Halide Double Perovskite for Sensitive Self‐Driven X‐ray Detection

Comprehensive Summary The lead‐free metal halide perovskites (MHPs) have emerged as prospective, environmentally friendly, and high‐performance candidates for X‐ray detection owing to their prominent X‐ray absorption capacity and low toxicity. Nevertheless, the energy consumption caused by high external operational voltages and severe ion migration limit the stability of lead‐free MHPs for X‐ray detection. Here, through the incorporation of alternating chiral–achiral spacer cations, we synthesized a novel lead‐free chiral‐polar perovskite, ( R ‐MPA) 2 (PA) 2 AgBiBr 8 ( 1R , R ‐MPA = R ‐methylphenethylammonium, PA = propylamine). The intrinsic spontaneous electric polarization yields an obvious bulk photovoltage (0.25 V), facilitating the separation and transport of photogenerated carriers, which makes self‐driven detection possible. Consequently, the 1R ‐based X‐ray detector achieves a high sensitivity (131 μC·Gy –1 ·cm –2 ) and a detection limit as low as 62.6 nGy·s –1 at 0 V bias. This study indicates the huge potential of chiral‐polar lead‐free MHPs in realizing superior self‐driven X‐ray detection, and provides an approach to the design of highly promising self‐driven X‐ray detection materials.