Rubidium germanium iodide

Rubidium germanium iodide is a ternary halide of rubidium and germanium, with the chemical formula RbGeI3. It is being considered as a potential counterpart to the toxic CH3NH3PbI3 for photovoltaic applications.

Preparation
Rubidium germanium iodide can be prepared by reacting germanium(II) hydroxide and rubidium iodide in hydroiodic acid:


 * Ge(OH)2 + RbI + 2 HI -> GeRbI3 + 2 H2O

Properties
Rubidium germanium iodide is polymorphic with various distorted perovskite-like structures, reflecting the influence of the "non-bonding" pair of electrons on the centre of Ge2+.

At room temperature, rubidium germanium iodide has a black, cubic perovskite form; between -29 °C and -52 °C a black rhombohedral form; a bordeaux-red orthrhombic perovskite form between -52 °C and -92 °C; and a lemon-yellow orthorhombic form below -92 °C.