Document Type : Research
Authors
1 ِDepartment of physics, Faculty of Modern Sciences and Technologies, Urmia University of Technology, Urmia
2 Departments of Physics, Condensed Matter Group, Faculty of Physics, Tabriz University, Tabriz
3 Faculty of Modern Sciences and Technologies, Urmia University of Technology, Urmia, Iran
Abstract
In this study, the structural, electronic, and optical properties of perovskite compounds Ba₃MBr₃ with nitrogen and phosphorus elements in the M-site were systematically investigated using density functional theory calculations. To increase the accuracy in modeling the electronic interactions, the second-order generalized gradient approximation was used, and calculations were performed both with and without considering the effects of spin-orbit coupling. In order to improve the prediction of the band gap, a hybrid Heyd-Scuseria-Ernzerhof (HSE) functional was used. The results showed that in the absence of SOC, the compound Ba₃NBr₃ has an indirect band gap of 0.36 eV, and Ba₃PBr₃ has a gap of 0.85 eV. By applying the HSE functional, these values increased to 0.92 and 1.40 eV, respectively. Considering SOC, the band gap of both compounds decreased slightly, which was more pronounced in the nitrogen compound. Density of states analysis showed that the p orbitals of Br play a major role in the valence band, while the conduction band is mainly composed of d orbitals of Ba. Electron density maps also confirmed the presence of ion-covalent bonds, such that the Ba–N bond has a stronger covalent character than the Ba–P bond. Overall, this study shows that the type of element substituted in the M site, as well as relativistic effects, has a significant impact on the electronic structure and band gap of these materials. These findings could pave the way for the design of stable and lead-free perovskites for novel optoelectronic applications.
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