Effects of alloying chalcopyrite CuTlSe2 with Na on the electronic structure and thermoelectric coefficients: DFT investigation
Laboratory of Quantum Physics of Matter and Mathematical Modeling (LPQ3M), Mascara University, Mascara, Algeria
2 Laboratory for Developing New Materials and Their Characterizations, Department of Physics, Faculté of Sciences, University Ferhat Abbas Setif 1, 19000, Sétif, Algeria
3 New Technologies - Research Center, University of West Bohemia, Univerzitni 8, 306 14, Pilsen, Czech Republic
4 Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, 11451, Riyadh, Saudi Arabia
Accepted: 6 December 2022
Published online: 15 December 2022
The optimized structural parameters, electronic structure, and thermoelectric coefficients of the chalcopyrite alloys Cu1–xNaxTlSe2, with x = 0.00, 0.25, and 0.50 were studied through density functional theory calculations. The Wu–Cohen generalized gradient and the Tran–Blaha modified Becke–Johnson approximations have been employed to describe the exchange–correlation potential. Energy band structure analysis reveals that CuTlSe2 is a semi-metal, while Cu0.25Na0.75TlSe2 and Cu0.50Na0.50TlSe2 alloys are semiconductors with gaps of approximately 0.17 eV and 0.35 eV, respectively. The total and partial densities of states were calculated and discussed. Examining the charge density, we point out the formation of the Na–Se ionic bond when Cu is replaced by the Na atom, which is responsible for the metal–semiconductor transition in the Cu1–xNaxTlSe2 alloys. Moreover, variations of the Seebeck coefficient, electrical conductivity, electronic and lattice thermal conductivity, power factor, and figure of merit of the Cu1–xNaxTlSe2 alloys with temperature and chemical potential were explored. The obtained results show that the value of the figure of merit increases when doping CuTlSe2 with sodium to reach 0.46 and 0.87 for p-type Cu0.75Na0.25TlSe2 and n-type Cu0.50Na0.50TlSe2, respectively.
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