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 toxic element lead and require for high operating voltages. Hence, it is imperative to explore environmentally friendly perovskite crystals without external bias for X-ray detection. Herein, we strategically introduce 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), which exhibit strong circular dichroism (CD) signals with an anisotropic g-factor reaching approximately 0.017. Significantly, the chiral-polar feature gives rise to distinctive spontaneous polarization, which leads 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 (SC) demonstrates a high sensitivity of 5.2 μC Gy_air⁻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.