X‐Ray Detection with High Dynamic Sensitivity and Ultra‐Low Detection Limits by Low‐Dimensional Hybrid Bismuth‐Iodides

Abstract Next‐generation halide perovskite X‐ray detectors require ultra‐low detection limits, high sensitivity across varying X‐ray intensities and low dark current. Starting from the non‐centrosymmetric 1D HDABiI ₅ (HBI) single crystals, the 1,6‐diamino hexane (HDA ²⁺ ) spacer is replaced by 1,8‐diamino octane (ODA ²⁺ ) to form 0D ODA ₃ Bi ₂ I ₁₂ (OBI), and by 3,6‐dioxa‐1,8‐diamino octane (EDEA ²⁺ ) to obtain 0D EDEA ₂ BiI ₆ ·4H ₂ O·I (EBI). At a low electric field of 0.9 V mm ⁻¹ and dose rate of 492 µGy _air s ⁻¹ , HBI, OBI, and EBI wafers exhibit X‐ray sensitivities of 5.6, 4.2, and 3.3 µC Gy _air ⁻¹ cm ⁻² , respectively. HBI has a sensitivity of 1988.98 µC Gy _air ⁻¹ cm ⁻² at only 8.18 V mm ⁻¹ and a dynamic sensitivity of 468.2 µC Gy _air ⁻¹ cm ⁻² at 0 V under X‐ray dose rate of 0.25 µGy _air s ⁻¹ . The detection limits for EBI, OBI, and HBI are 110, 4.1, and <4 nGy _air s ⁻¹ . A uniform ionic distribution and spontaneous ferroelectricity in the 1D BiI ₆ octahedral network of HBI, combined with structural rigidity, enable low‐voltage operation, surpassing the capabilities of CdTe and α‐Se detectors. Additionally, HBI wafers show a piezoelectric coefficient of d ₃₃ ≈ 0.78 pm V ⁻¹ , and pyroelectric current of ≈5 nA near 120 °C, coinciding with abrupt lattice expansion and reduced thermal conductivity.