Zero-Dimensional Indium-Based Multiaxial Ferroelectric for X-Ray Detection

Ferroelectric polarization can achieve efficient electron and hole extraction to solve the difficulties of high exciton binding energy, poor charge transport, and relatively low sensitivity for 0D perovskite X-ray detectors. However, the device performance of X-ray detectors based on uniaxial ferroelectrics is limited by misalignment between polarization direction and charge collection direction. Here, we present the first demonstration of a multiaxial ferroelectric, (TMP)(Me-TMP)InBr₆ (TMP ═ C₄H₁₀NS⁺, Me-TMP═ C₅H₁₃NS²⁺), for X-ray detection and confirm that it is angular-independent of X-ray. Polarization-electric field hysteresis loops reveal remarkable saturation polarization values of 3.88 and 13.2 µC/cm². The multiaxial ferroelectric polarization drives efficient carrier separation and transport, suppressing exciton binding energy to 96.8 meV and extending carrier lifetime to 1.81 ms, which yields an outstanding mobility-lifetime product of 10^-3 cm² V^-1. Coupled with ultrahigh bulk resistivity (10¹² Ω cm) for minimized dark current, these properties enable a record sensitivity of 12510 µC Gy_air ^-1 cm^-2 under 24 V/mm. Notably, the self-powered mode (0 V) achieves 806 µC Gy_air ^-1 cm^-2 sensitivity via a ferroelectric-induced built-in electric field. Meanwhile, it realizes an extremely high ion migration activation energy (1.35 eV), mitigating operational degradation.