<p>Formamidinium lead iodide (FAPbI₃) perovskite exhibits an impressive X-ray absorption coefficient and a large carrier mobility-lifetime product (µτ), making it as a highly promising candidate for X-ray detection application. However, the presence of larger FA⁺ cation induces to an expansion of the Pb-I octahedral framework, which unfortunately affects both the stability and charge carrier mobility of the corresponding devices. To address this challenge, we develop a novel low-dimensional (HtrzT)PbI₃ perovskite featuring a conjugated organic cation (1H-1,2,4-Triazole-3-thiol, HtrzT⁺) which matches well with the α-FAPbI₃ lattices in two-dimensional plane. Benefiting from the matched lattice between (HtrzT)PbI₃ and α-FAPbI₃, the anchored lattice enhances the Pb-I bond strength and effectively mitigates the inherent tensile strain of the α-FAPbI₃ crystal lattice. The X-ray detector based on (HtrzT)PbI₃(1.0)/FAPbI₃ device achieves a remarkable sensitivity up to 1.83 × 10⁵ μC Gy_air⁻¹&#xa0;cm⁻², along with a low detection limit of 27.6 nGy_air s⁻¹, attributed to the release of residual stress, and the enhancement in carrier mobility-lifetime product. Furthermore, the detector exhibits outstanding stability under X-ray irradiation with tolerating doses equivalent to nearly 1.17 × 10⁶ chest imaging doses.</p>