X‐ray detectors are widely used, e.g., in medical diagnostics or for product inspection. Halide perovskites are promising as materials for direct X‐ray detection. In direct X-ray detection, a semiconductor material converts X-ray photons to an electrical charge, and thus, directly into a digital signal. However, obtaining high-quality perovskite crystals with large sizes and long-term stability that can be used in detectors is challenging.

Xiaojia Zheng, Wen‐Hua Zhang, Sichuan Research Center of New Materials, China Academy of Engineering Physics, Chengdu, Jianguo Zhu, Sichuan University, Chengdu, China, and colleagues have prepared methylammonium bismuth iodide (MA₃Bi₂I₉) polycrystalline pellets (PPs, pictured above on the right) to be used in direct X‐ray detectors. The team used MA₃Bi₂I₉ powders (pictured above on the left) as the raw materials. The powders were compacted under a pressure of 0.2 GPa using a cold isostatic press method. The size and shape of the resulting pellets can be easily tuned by using different molds.

The team then assembled X‐ray detectors with the configuration Au/MA₃Bi₂I₉‐PPs/Au and evaluated the system’s X‐ray detection performance. The devices showed a low limit of detection, high detection efficiency, high sensitivity, and good ambient and thermal stability. Based on these properties, as well as their nontoxicity and simple fabrication, the team considers MA₃Bi₂I₉‐PPs detectors good candidates for next-generation X-ray detectors.

• Robust Fabrication of Hybrid Lead-Free Perovskite Pellets for Stable X-Ray Detectors with Low Detection Limit,
  Shujie Tie, Wei Zhao, Deyu Xin, Min Zhang, Jidong Long, Qi Chen, Xiaojia Zheng, Jianguo Zhu, Wen-Hua Zhang,
  Adv. Mater. 2020.
  https://doi.org/10.1002/adma.202001981