Impact of pressure on structural, mechanical, optoelectronic and thermoelectric properties of vacancy-ordered double perovskite K2SeCl6: A first principles study

Abstract

The structural, mechanical, electronic, optical, and thermoelectric properties of vacancy-ordered double perovskite K${}_2$SeCl${}_6$ are estimated through first-principle calculations under ambient conditions and hydrostatic pressures up to 80 GPa. The structural stability of the material is confirmed by a Goldsmith tolerance factor of 0.98 and a negative formation energy of −0.53 eV/atom. K${}_2$SeCl${}_6$ is mechanically robust, possessing good stability, hardness, and stiffness. At ambient conditions, K${}_2$SeCl${}_6$ exhibits p-type semiconducting behavior with an indirect band gap of 2.502 eV. Under 80 GPa, the band gap of the material reduces to the lower boundary of the visible region. Optical absorbance and conductivity increase with increase of hydrostatic pressure, enhancing its suitability for ultraviolet–visible optoelectronic applications as an absorption layer in photovoltaic cells under pressure. Additionally, its low lattice thermal conductivity and high thermoelectric figure of merit suggest its efficiency for renewable energy applications both at ambient and high-pressure conditions. This material shows promising multifunctionality for future optoelectronic and energy conversion technologies.