Investigations on the Electronic and Optical Properties of Double Perovskites Ba₂BiSbO₆

Recent research on double perovskites with large spin-orbit coupling (SOC) assisted materials are of great interest due to their novel properties. Materials with band gap in the visible range are found suitable for opto-electronic devices. Depending on the types of gaps (indirect or direct), materials can be used for photo detectors or optoelectronic emitters. Using first principle density functional (DF) approach, we study the electronic and optical properties of newly synthesized Ba₂BiSbO₆. Within generalized gradient approximation without SOC, an indirect band gap of 1.85 eV was observed which reduces to 1.72 eV when SOC is taken into account. Significant changes due to SOC has been found at Gamma point in the band structure where band splitting of ~1.3 eV has been observed just above the fermi level with possible indication from indirect to direct band gap semiconductor. Strong hybridization between Bi-6p, Sb-5p and O-2p states observed on the electronic density of states. Optical study shows interband electron transition with energy larger than the bandgap of the material. This suggests Ba₂BiSbO₆ as a candidate material for photodetectors (absorbers).