Structural, optoelectronic, thermoelectric, and thermodynamic properties of novel copper-based halide double perovskites Cs 2 CuXCl 6 (X = Sb, As, Bi): First principles insights

In the present investigation, a complete physical study of electronic structure, optical, thermoelectric and thermodynamic properties have been done on a set of three lead-free double halide perovskite materials, Cs ₂ CuXCl ₆ ; using the first principle calculation on the basis of Density Functional Theory and the theory of Boltzmann transport applied in the WIEN2K simulator program. When substituting the X with As, Sb and Bi cation in the double perovskite structure Cs ₂ CuXCl ₆ , interesting electronic and optical properties have been shown, namely low indirect band gap of 0.78, 1.21 and 1.51 eV for Cs ₂ CuAsCl ₆ , Cs ₂ CuSbCl ₆ and Cs ₂ CuBiCl ₆ respectively, as well as high absorption in the UV-Visible region. Among the three studied compounds, Cs ₂ CuAsCl ₆ exhibits an excellent structural stability regarding its high bulk modulus and maximum tolerance factor. It is noticeable from the thermoelectric study that Seebeck coefficient decreases with increasing temperature, while the figure of merit is proportional with temperature enhancement, such a behavior makes of the investigated materials promising candidates for visible-light solar cell device applications, especially that our theoretical results match perfectly with previous works ^[1] .