Low Bandgap 2D Perovskite Single Crystal with Anomalous-large Charges/ions Collection Ratio for Ultra-sensitive and Stable X-ray Detectors.

The low-dimensional halide perovskites have attracted increasing attention due to their improved moisture stability, reduced defects, and suppressed ions migration in many optoelectronic devices such as solar cells, light-emitting diodes, X-ray detectors, and so on. However, they are still limited by their large band gap and short charge carriers' diffusion length. Here, we demonstrate that the introduction of metal ions into organic interlayers of two-dimensional (2D) perovskite by cross-linking the copper paddle-wheel cluster-based lead bromide ([Cu(O C-(CH ) -NH ) ]PbBr ) perovskite single crystals with coordination bonds can not only significantly reduce the perovskite band gap to 0.96 eV to boost the X-ray induced charge carriers, but can also selectively improve the charge carriers' transport along the out-of-plane direction and blocking the ions motion paths. The [Cu(O C-(CH ) -NH ) ]PbBr single-crystal device can reach a record charges/ions collection ratio of 1.69×10 ±4.7 % μGy  s, and exhibit a large sensitivity of 1.14×10 ±7% μC Gy  cm with the lowest detectable dose rate of 56 nGy  s under 120 keV X-rays irradiation. In addition, [Cu(O C-(CH ) -NH ) ]PbBr single-crystal detector exposed to the air without any encapsulation shows excellent X-ray imaging capability with long-term operational stability without any attenuation of 120 days.