First-Principles Calculations to Investigate Direct-Band Novel Cobalt-Based Double Perovskite Materials for Optoelectronic Applications

Abstract

A series of novel cobalt-based perovskite materials have been studied through density functional theory first-principles calculation. The cubic perovskite structure stability is demonstrated by tolerance factors and Born−Huang stability criteria in mechanics as well as formation energies in thermodynamics. The elastic constant analysis indicates that the fluoride perovskites are ductile and ionic compounds while the chloride perovskites are brittle and covalent. All the perovskites are direct semiconductors with band gaps as 1.644, 0.455, 2.136, and 0.683 eV for K 2 InCoF 6 , K 2 InCoCl 6 , Rb 2 InCoF 6 , and Rb 2 InCoCl 6 , respectively. The absorption coefficient reveals all the materials still have broad absorption spectra compared with solar AM1.5 irradiance despite photon unavailability in the small wavelength range. Taking into account other physical properties, these perovskites still exhibit great potential and deserve further experimental research. Due to a proper band gap value and high light absorption, K 2 InCoF 6 is considered as the best candidate for solar materials.