Synthesis, Properties, and Modeling of Cs1–xRbxSnBr3 Solid Solution: A New Mixed-Cation Lead-Free All-Inorganic Perovskite System

In the present work, the substitution of cesium (Cs+) with rubidium (Rb+) in fully inorganic tin bromide perovskites Cs1–xRbxSnBr3, has been experimentally demonstrated by synthesizing pure single-phase samples in the CsSnBr3–Cs0.70Rb0.30SnBr3 compositional range. The substitution of Cs with Rb is responsible for structural modification from cubic to orthorhombic symmetry, which has been correlated with optical properties, as the band gap varies from 1.719 to 1.817 eV from CsSnBr3 to Cs0.70Rb0.30SnBr3 sample. Notably, all of the rubidium-embedding alloys present good air stability. All of these results are very straightforward and open the possibility to exploit the electrical and optical capabilities of this very promising family of lead-free materials.