Chirality Inducing Polar Photovoltage in a 2D Lead-Free Double Perovskite toward Self-Powered X-ray Detection

Lead-free halide double perovskites (HDPs) have sparked broad interest in developing “green” photodetectors; however, self-powered X-ray detectors in this family remain elusive. Here, by exploiting the chirality-induced polar photovoltaic effect in a chiral-polar 2D HDP, ( R -MPA) 4 AgBiI 8 ( 1, R -MPA = R -β-methylphenethylammonium), we successfully realized self-powered X-ray detection. The significant spontaneous electric polarization in 1 gives it a large polar photovoltage of 0.36 V, which drives the separation and transport of X-ray-generated carriers, thus acquiring the capability of self-powered detection. Consequently, X-ray detectors based on high-quality single crystals of 1 exhibit a high sensitivity of 46.3 μC Gy –1 cm –2 and an ultralow detection limit of 85 nGy s –1 at zero bias. The sensitivity can be further increased to 949.6 μC Gy –1 cm –2 at 50 V bias, outperforming all current 2D HDP detectors. Our work is the first to demonstrate self-powered X-ray detection in single-phase lead-free HDPs, enlightening future design of “green” self-powered radiation detectors.