An X-ray detector with an ultra-low detection limit based on bulk two-dimensional perovskite PEA2PbBr4 single crystals grown in HBr solution†

Achieving a lower detection limit is always crucial for X-ray detectors in medical imaging. Two-dimensional (2D) perovskites are superior candidate materials for X-ray detection due to their high bulk resistivity, excellent environmental stability, and negligible ion migration under high bias. However, the reported detection limit of 2D perovskite X-ray detectors still apparently lags behind that of their 3D analogues due to the difficulty in the growth of high-quality bulk 2D perovskite single crystals (SCs). Herein, we demonstrate an X-ray detector with an ultra-low detection limit based on high-quality bulk PEA₂PbBr₄ SCs grown in HBr solution for the first time. According to the solubility difference of reactants, a slowly varying nucleation curve for the precursor solution is designed to stabilize growth rate and reduce defect density during crystal growth. The fabricated Au/PEA₂PbBr₄/Au detector shows a low noise level of 10⁻⁵ nA Hz^−1/2 and an ultra-low dark current drift of 6.6 × 10⁻⁷ pA cm⁻¹ V⁻¹ s⁻¹. Together with a commendable hole lifetime of 2.76 μs and hole mobility-lifetime product of 5.8 × 10⁻⁴ cm² V⁻¹, the produced detector exhibits a high sensitivity of 2998 μC Gy_air s⁻¹ cm⁻² and a record-low detection limit of 0.79 nGy_air s⁻¹. The current work would be beneficial for the development of next generation medical imaging.