First-principles study of anti-perovskites Ca4Pn2O (Pn = As, Sb, Bi) as a potential optical material

Abstract

Anti-perovskite materials have potential applications in solid-state batteries, high-temperature thermoelectric devices and optical devices. In the current work, through the first principle calculations, we find that Anti-perovskites Ca4Pn2O (Pn = As, Sb, and Bi) have the gradually decreased band gaps of 2.078, 1.885 and 1.688 eV (HSE06 method), respectively due to the gradually increased covalent components of Ca–O and Ca-Pn (As, Sb, Bi) bonds with the increasing atomic numbers of As, Sb and Bi. The effective carrier masses of Ca4Pn2O (Pn = As, Sb, Bi) intrinsic semiconductors are small, and decrease in the principal directions. The large absorption coefficients and small effective carrier masses promise Ca4Pn2O (Pn = As, Sb, Bi), especially Ca4Bi2O, to be p-type visible light-absorbing semiconductor materials. The Raman spectra of Ca4Pn2O (Pn = As, Sb, and Bi) contain the double degenerate mode Eg and single mode A1g while the infrared spectra contain the double degenerate mode Eu and single modes A2u and B1u. This work provides valuable information for future research on Ca4Pn2O (Pn = As, Sb, Bi) anti-perovskites.