Structure design of lead-free chiral-polar perovskites for sensitive self-powered X-ray detection

Metal halide perovskites have made significant progress in X-ray detection owing to their exceptional optoelectronic properties. However, most of these materials suffer from the toxic element lead and the requirement for high operating voltages. Hence, the exploration of environmentally friendly perovskites for X-ray detection without external bias is imperative. Herein, we strategically introduced chiral cations to synthesize a pair of lead-free chiral-polar hybrid perovskites (S-MPz)6Bi3I21･6H2O and (R-MPz)6Bi3I21･6H2O (1S and 1R, S/R-MPz = S/R-2-methylpiperazinium). They exhibited strong circular dichroism signals with an anisotropic g-factor reaching approximately 0.017. Significantly, the chiral-polar feature gave rise to distinctive spontaneous polarization, which led to a photovoltage of 1.1 V under X-ray illumination, endowing self-powered detection capabilities for X-ray. Further exploration of X-ray devices based on 1R single crystal demonstrated a high sensitivity of 5.2 μC Gyair−1 cm−2 at zero bias. This study realizes passive X-ray detection depending on the intrinsic spontaneous polarization induced built-in electric field of chiral-polar perovskite, providing an effective approach to the chemical design of desired materials for high-performance "green" self-powered radiation detection.