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

ABSTRACT 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)InBr ₆ (TMP ═ C ₄ H ₁₀ NS ⁺ , Me‐TMP═ C ₅ H ₁₃ NS ²⁺ ), 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/cm ² . 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 cm ² V ⁻¹ . Coupled with ultrahigh bulk resistivity (10 ¹² 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.