Investigation of cubic K2NaXBr6(X=Sc, Y) double perovskites for optical and thermoelectric devices

In this work, electronic, structural, optical, thermoelectric and elastic characteristics of K2NaXBr6(X = Sc, Y) are studied by applying first principles method. The analysis of band structure (BS) and density of states (DOS) revealed the direct wide band gap (Eg) at l' symmetry points. The Eg value is 3.72 eV for K2NaScBr6 and 5.04 eV for K2NaYBr6. The tolerance factor (r) for K2NaScBr6 and K2NaYBr6 are 0.9 and 1.0, correspondingly which confirm the cubic nature of mentioned compounds. Both compounds show negative values of formation energies which confirm their stable structure. The absorption of optical factors lies in ultra-violet (UV) region which make them suitable for photovoltaic devices. The elastic features verify ductility, anisotropy, and mechanical stability of K2NaXBr6(X = Sc, Y). The thermal conductivity (k/r), see-beck coefficient (S), figure of merits (ZT) and electrical conductivity (a/r) are also calculated using Boltz-Trap code. Thermoelectric and optical characteristics showed that investigated perovskites are suitable for renewable energy applications.

Automated summary

In this work, the electronic, structural, optical, thermoelectric and elastic characteristics of K2NaXBr6(X = Sc, Y) were studied using first principles method. The analysis revealed a direct wide band gap at l' symmetry points with Eg values of 3.72 eV for K2NaScBr6 and 5.04 eV for K2NaYBr6. The compounds showed stable cubic structures with tolerance factors of 0.9 and 1.0 for K2NaScBr6 and K2NaYBr6 respectively. The optical factors indicated suitability for photovoltaic devices in the UV region, and the elastic features confirmed ductility, anisotropy, and mechanical stability. Thermoelectric and optical characteristics showed potential for renewable energy applications.