Cs2NaVCl6 : a Pb-Free Halide Double Perovskite with Strong Visible and Near-Infrared Light Absorption

Developing the environmentally-friendly, stable as well as narrow and direct bandgap halide perovskite materials has attracted substantial interests due to their potential wide applications. Here, an all-inorganic Pb-free halide double perovskite, Cs2NaVCl6, was prepared by solid state reaction method and hydrothermal method. It crystallizes in cubic Fm-3m space group with unit parameter of a=10.3497(14) A. The combined density functional theory and experimental study demonstrates that the compound is a direct band gap semiconductor with bandgap of ~2.64 eV. More importantly, it exhibits strong visible and near-infrared light absorptions and markedly ambient and thermal stability.