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<p>In the current research work, we present a comprehensive study of the electronic and optical properties of heavy rare-earth–based thallium diselenides, TlRSe<sub>2</sub> (R = Dy, Ho, Er). Spin-polarized electronic structure calculations were performed using the PBE-GGA and TB-mBJ exchange–correlation potentials.The spin-up band gaps were obtained as 2.04&#xa0;eV and 2.46&#xa0;eV using PBE-GGA, and 3.10&#xa0;eV and 3.51&#xa0;eV using TB-mBJ for TlDySe<sub>2</sub> and TlErSe<sub>2</sub>, respectively, whereas the spin-down electronic states reveal zero band gaps for TlDySe<sub>2</sub> and TlErSe<sub>2</sub>, confirming their half-metallic character. TlHoSe<sub>2</sub> shows a finite bandgap for both the spins. For spin up, band gap value found to be ~ 2.50&#xa0;eV using PBE-GGGA and 2.30 using TB-mBJ, whereas for spin down, band gap value found to be ~ 0.42&#xa0;eV using PBE-GGGA and 0.65 using TB-mBJ. The observed behaviour represents the semicondunting nature of TlHoSe<sub>2</sub>. The optical properties, evaluated using the TB-mBJ potential, demonstrate good agreement with the Penn model. The calculated static dielectric constants were found to be ~ 15.0, 6.5, and 11.0, and corresponding static refractive indices are 3.90, 2.54, and 3.40 for TlDySe<sub>2</sub>, TlHoSe<sub>2</sub> and TlErSe<sub>2</sub>, respectively. The negligible absorption in the infrared region for TlDySe<sub>2</sub> and TlErSe<sub>2</sub> reflects their metallic response, whereas the absence of infrared absorption in TlHoSe<sub>2</sub> verifies its semiconducting behavior. Moreover, the strong ultraviolet absorption indicates that TlRSe<sub>2</sub> compounds have significant potential for UV absorber applications, including photovoltaics, photodetectors, and UV-shielding technologies.</p>

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First-principles exploration of the optoelectronic properties of ternary rare-earth selenides

  • 期刊论文

  • 发表日期：

    2026年3月17日

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  • Praveen Kumar,
  • Arvind Kumar,
  • Raj Kumar,
  • Annveer Singh,
  • Upendra Kumar,
  • Rachana Sain,
  • Rishi P. Singh

摘要

In the current research work, we present a comprehensive study of the electronic and optical properties of heavy rare-earth–based thallium diselenides, TlRSe2 (R = Dy, Ho, Er). Spin-polarized electronic structure calculations were performed using the PBE-GGA and TB-mBJ exchange–correlation potentials.The spin-up band gaps were obtained as 2.04 eV and 2.46 eV using PBE-GGA, and 3.10 eV and 3.51 eV using TB-mBJ for TlDySe2 and TlErSe2, respectively, whereas the spin-down electronic states reveal zero band gaps for TlDySe2 and TlErSe2, confirming their half-metallic character. TlHoSe2 shows a finite bandgap for both the spins. For spin up, band gap value found to be ~ 2.50 eV using PBE-GGGA and 2.30 using TB-mBJ, whereas for spin down, band gap value found to be ~ 0.42 eV using PBE-GGGA and 0.65 using TB-mBJ. The observed behaviour represents the semicondunting nature of TlHoSe2. The optical properties, evaluated using the TB-mBJ potential, demonstrate good agreement with the Penn model. The calculated static dielectric constants were found to be ~ 15.0, 6.5, and 11.0, and corresponding static refractive indices are 3.90, 2.54, and 3.40 for TlDySe2, TlHoSe2 and TlErSe2, respectively. The negligible absorption in the infrared region for TlDySe2 and TlErSe2 reflects their metallic response, whereas the absence of infrared absorption in TlHoSe2 verifies its semiconducting behavior. Moreover, the strong ultraviolet absorption indicates that TlRSe2 compounds have significant potential for UV absorber applications, including photovoltaics, photodetectors, and UV-shielding technologies.