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

Developing environmentally friendly, stable, and narrow and direct band gap halide perovskite materials has attracted substantial interest because of their wide range of potential applications. Here, an all-inorganic Pb-free halide double perovskite, Cs2NaVCl6, was prepared by the solid-state reaction method and hydrothermal method. Cs2NaVCl6 crystallizes in the cubic Fm3̅m space group with the unit parameter a = 10.3497(14) Å. The combined density functional theory and experimental study demonstrates that the compound is a direct band gap semiconductor with a band gap of ∼2.64 eV. More importantly, it exhibits strong visible and near-infrared light absorptions and markedly ambient and thermal stability.