Perovskitizer Tuning Pb²⁺ 6s² Lone Pair Effects in Hybrid Perovskite Halide Enables Multiaxial Self-Powered X-Ray Detection

The stereochemical expression of the ns(2) lone pair significantly impacts symmetry breaking and corresponding photoelectric properties. However, hindered by the symmetric octahedral configuration, the Pb2+ 6s(2) lone pair in the well-conductive lead halide hybrid perovskites (LHHP) are normally stereo-inactive, new approaches to activate the 6s(2) lone pair are still greatly desired. Herein, by exploiting a perovskitizer tuning Pb2+ lone pair method, the study successfully obtains a stereo-active 6s(2) in the polar perovskite PA2MHy2Pb3Br10 (PMPB, PA = n-propylamine, MHy = methylhydrazine), and unprecedentedly performs a multiaxial self-powered X-ray detection. In detail, the stereo-active 6s2 lone pair is caused by the coordination bond between the perovskitizer MHy and Pb atom. Emphatically, the N-Pb bond induces a large angular distortion parameter (approximate to 45 times larger than other LHHP) and the lowest-symmetric space group (P1) crystallization. Therefore, PMPB natively contains multiaxial polarization, which acts as the driving force to separate and transport the X-ray-generated carriers, thus enabling multiaxial self-powered X-ray detection with a low detection limit (129 nGy s(-1)). This work reveals the relationship between stereo-active lone pair and polarization and sheds light on future X-ray detection.