Electronic, optical and thermoelectric properties of the CsMF3 (M= Si or Ge) fluoro-perovskites

Abstract

In this paper, the structural, electronic and optical properties of inorganic fluoroperovskites CsMF3 (M = Si or Ge) are investigated by using the density functional theory calculations (DFT) with the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE). The optimized equilibrium lattice parameters of the studied compounds are calculated and found to be 4.46 Å and 4.57 Å for CsSiF3 and CsGeF3, respectively. These values are exploited to compute the electronic and optical properties of the materials CsSiF3 and CsGeF3. From electronic results, it is found that the studied compounds exhibit a p-type semi-conductor characters with direct band gap which are equal to 1.20 eV and 2.06 eV for CsSiF3 and CsGeF3, respectively. Moreover, the optical properties are calculated to explore the potential of the studied materials for optoelectronic applications. In addition, other physical properties are investigated such as the Seebeck coefficient (S), the thermal conductivity over relaxation time (k⁄τ), the electrical conductivity over relaxation time (σ⁄τ), the figure of merit (ZT) and the power factor (PF) estimated as a function of temperature (T) by using the semi-classical Boltzmann transport theory within BoltzTraP code. Our results revel that the compounds CsSiF3 and CsGeF3 are promising candidates in the photovoltaic applications. Also, the inorganic fluoroperovskites CsMF3 (M = Si or Ge) could be used for the thermoelectric devices.