Dion-Jacobson copper-based perovskite (BDA)CuBr4 with narrow interlayer spacing for highly Stable and sensitive X-ray detection

A Dion–Jacobson lead-free copper perovskite (BDA)CuBr₄ with a narrow 4.5 Å interlayer spacing. • Single-crystal X-ray detector achieves high sensitivity of 520.2 μC Gy⁻¹ cm⁻² at 50 V. • Detection limit as low as 283 nGy s⁻¹, well below the medical diagnostic dose rate. • Strong N–H···Br hydrogen bonding and tight stacking ensure excellent long-term stability. Metal halide perovskite materials, especially lead-based systems, have become a research hotspot for high-performance X-ray detectors due to their excellent optical absorption coefficients and high carrier mobilities. However, the environmental and biological risks associated with lead-containing components hinders their widespread commercial adoption, making the development of lead-free alternatives an urgent priority. Copper-based perovskites show considerable promise because of their non-toxicity and abundant raw material reserves, but their X-ray detection performance and stability still require further improvement. In this work, a Dion–Jacobson (DJ)-type lead-free copper-based perovskite, (BDA)CuBr₄, was synthesized via a slow cooling solution method. The incorporation of the diamine 1,4-butanediamine (BDA) enables adjacent inorganic layers to be connected through covalent bonds, which not only enhances structural stability but also results in a narrow interlayer spacing of 4.5 Å, thereby facilitating efficient interlayer carrier transport. The single-crystal X-ray detector fabricated from this material delivers outstanding performance: a sensitivity of 520 μC Gy -1 cm -2 at a bias of 50 V, an extremely low dark current drift of 4.21 × 10 -6 nA cm -1 s -1 V -1 , and a limit of detection as low as 283 nGy s⁻¹. No evident fatigue is observed under multiple on/off switching cycles at high-dose-rate X-ray irradiation, and the device performance remains stable after 60 days of storage. This lead-free copper-based perovskite provides an effective solution to balance the performance and environmental compatibility of conventional detection materials, paving the way for the development of next‑generation high‑performance, lead‑free X‑ray detectors.