A DFT study of optoelectronic, elastic and thermo-electric properties of the double perovskites Rb2SeX6 (X Br,Cl)
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Date
2023-04-29
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Journal of the Nigerian Society of Physical Sciences
Abstract
Thermo-electric (TE) material applications reduce reliance on traditional energy resources by converting heat to electric energy. We have stud-
ied, for the first time, the thermo-electric properties of Rb 2 SeX 6 (X Br,Cl). Using norm-conserving pseudo potentials in a plane wave basis set
of Quantum Espresso code, the optoelectronic, elastic and thermo-electric properties of Rb 2 SeX 6 (X Br,Cl) have been investigated using den-
sity functional theory. Generalized Gradient Approximation of Perdew Burke Ernzerhof (GGA-PBE) and Generalized Gradient Approximation
of Perdew Burke Ernzerhof adapted for Solid (GGA-PBESol) exchange correlation functionals were employed in all calculations. The band
structure plots suggest that the studied double perovskites have indirect band gaps. Rb 2 SeBr 6 band gap values of 1.7574/ 1.569 eV (using GGA-
PBE/PBEsol) are remarkably similar to that of two effective inorganic/organic perovskites FAPbI 3 and MAPbI 3 . Maximum peaks generated from
refractive index results indicate possible solar cell uses of the materials because they are in the visible and ultraviolet ranges. The results of
other optical properties such as absorption coefficients, electron energy loss, conductivity, and reflectivity concludes that Rb 2 SeX 6 (X Br,Cl) have
good values for electron generation, high potential for applications in the optoelectronic industry and are semiconductor in nature. The calculated
shear anisotropy values of Rb 2 SeBr 6 /Cl 6 are 3.09/1.71, suggesting that they are isotropic materials. With calculated Poisson’s ratio of 0.32 and
0.26, the materials are predicted to be ductile in nature. The two materials are appropriate for thermo-electric applications since their thermal to
electrical conductivity ratio are small (the order of 10 −5 ). The calculated minimum values of Seebeck coefficient values of 0.198 × 10 3 / 0.166 ×
10 3 (m V/K) at 750 K, for Rb 2 SeBr 6 /Cl 6 are positive, indicating that they have p-type conduction. Figure of merit values at all temperature range
considered are greater than one (ZT > 1) for both Rb 2 SeBr 6 and Rb 2 SeCl 6 , suggesting that they are good thermo-electric materials. The results of
the calculations provide the basis for the industrial application of Rb 2 SeBr 6 /Cl 6 as solar cells.
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Citation
W. A. Yahya, A. A. Yahaya, A. A. Adewale, A. A. Sholagberu, N. K. Olasunkanmi (2023).