DFT Study of Electronic, Optical and Thermoelectric Properties of Doped and Undoped Calcium Oxide

Abstract

Calcium Oxide is a potential candidate for thermal energy storage at high temperatures in the range of 450-600 °C. the reversible solid gas reaction of Ca(OH)2/CaO system offers high energy density, long storage period and cost effectiveness. Our aim in this work is to explore it as a potential thermoelectric and optoelectronic material by tuning its band gap by different metal doping and creation of oxygen vacancies. Density functional theory technique is used to model the electronic, optical, and thermoelectric properties of modified and unmodified materials. Calcium oxide is a wide band gap material having an indirect band gap of 6.0 eV while a direct band gap of 7.1 eV has been determined experimentally. Therefore, to tune its band gap, it was doped with cadmium and zinc (25% each), while 25% and 3.12% oxygen vacancies were created in pure CaO. it was found that the indirect band gap was reduced to 4.47 eV and 4.25 eV for Zn and Cd doping respectively, while 25% and 3.12% oxygen vacancy reduced the band gap to 1.51 eV and 3.19 eV respectively. CaO with 3.12% Oxygen vacancy was found to have the highest figure of merit which makes it potential thermoelectric material. In the visible region, 25% Oxygen doped was found to have the highest absorption compared to all systems which makes it potential material for solar cell fabrication