Electronic and Thermoelectric Properties of Yb ^2+ -Doped Cubic Perovskite CsCaCl _3 : A First-Principles Study

First-principles calculations are used to study the structural, electrical, and thermoelectric properties of pure and Yb ^2+ -doped CsCaCl _3 perovskite. Thermoelectric transport properties as a function of chemical potentials ( μ ), temperature (T), and Yb ^2+ dopant concentration (x) are computed using semi-classical Boltzmann theory implemented in the BoltzTrap code. The calculated indirect bandgap of pure CsCaCl _3 is 5.35 eV, and it behaves like an insulator. To tailor the electronic and thermoelectric properties of the CsCaCl _3 compound, we considered substitutional doping with the lanthanide Yb ^2+ atom for possible desired applications. According to the predicted formation energy, Yb ^2+ -doped at the cation site (Ca-site) is structurally more stable than at the anion site. Within the bandgap of pure CsCaCl _3 , the Yb ^2+ dopant induces defective states. As a result, transitions from insulator to semiconductor and indirect to direct bandgap occurred. According to the partial density of states, the Yb ^2+ atom’s f-orbital produced impurity states above the valance band maximum (VBM), resulting in a narrower bandgap. For both values of chemical potential ( μ = conduction bad minimum [CBM] and VBM), we characterize the thermoelectric properties. Additionally, various Yb ^2+ dopant concentrations were taken into account. At μ = CBM, substitutional Yb ^2+ doping at a concentration level of 1.67 % demonstrates an improvement in the thermoelectric properties. The highest ZT value for CsCaCl _3 :Yb ^2+ 1.67 % at μ = CBM is 1.4 at 1150 K. According to the ZT value, Yb ^2+ -doped CsCaCl _3 cubic perovskite compound can be used in thermoelectric applications.