Layered hybrid organic–inorganic lead halides are materials with perovskite-type structures, unique optoelectronic properties, and a range of possible applications. The exact structure of the material determines its optoelectronic properties.

Maksym V. Kovalenko, Swiss Federal Institute of Technology (ETH) Zurich, and Empa − Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, both Switzerland, and colleagues have synthesized a new layered hybrid lead halide. The team combined formamidinium acetate with guanidinium carbonate, lead acetate, and hydroiodic acid to create the desired GFAPbI₄ material as needle-shaped crystals (G = guanidinium, pictured bottom right; FA = formamidinium, pictured top left).

The crystalline material is stable up to 225 °C and shows red luminescence with a quantum yield of 3.5 % at room temperature. It also is photoconductive, which means it has a higher electrical conductivity when irradiated than in the dark. According to the researchers, these results showcase the structural diversity that can be achieved with lead halide perovskites.

• Guanidinium-Formamidinium Lead Iodide: A Layered Perovskite-Related Compound with Red Luminescence at Room Temperature,
  Olga Nazarenko, Martin R. Kotyrba, Sergii Yakunin, Marcel Aebli, Gabriele Rainò, Bogdan M. Benin, Michael Wörle, Maksym V. Kovalenko,
  J. Am. Chem. Soc. 2018.
  https://doi.org/10.1021/jacs.8b00194