Optoelectronics and thermoelectric performances in CuX (X = F, Cl, Br, and I)

The current study focused on examining the structural, mechanical, and optoelectronic properties of CuF, CuCl, CuBr, and CuI by the utilisation of the FP-LAPW method. The calculations reveal that GGA is a better fit than LDA for evaluating structural characteristics, including lattice parameters and bulk modulus. The examination of the band structure reveals that CuF exhibits metallic behaviour, whilst the compounds CuCl, CuBr, and CuI exhibit semiconducting properties, characterised by direct fundamental gaps (Γ → Γ) of 0.516, 0.425, and 1.049 eV, respectively. The peak absorption values for CuCl, CuBr, and CuI are located at 10.68 eV, 9.53 eV, and 7.68 eV, respectively. All materials have ultraviolet absorption peaks. Therefore, the compounds demonstrate substantial absorption in the low- and mid-ultraviolet wavelengths. The four compounds exhibit anisotropic properties, possess ductility, and demonstrate mechanical stability. These entities possess the ability to endure a wide range of temperatures. The thermoelectric performance of the three semiconductors, CuCl, CuBr, and CuI, was investigated. At 300 K, the k L values for CuBr, CuCl, and CuI, are 2.89 W/mK, 3.98 W/mK, and 3.56 W/mK, and the Gruneisen values are as follows: γ (CuCl) = 2.4087, γ (CuBr) = 2.4747, and γ (CuI) = 2.1962. At a temperature of 600 K, the k T value is found to be relatively low. The measured values for the k T of CuCl, CuBr, and CuI are around 1.7818 W m−1 K−1, 1.5109 W m−1 K−1, and 2.8580 W m−1 K−1, respectively. At a temperature of 300 K, the Seebeck coefficients (S) for CuCl, CuBr, and CuI are measured to be 1192.7964 μV/K, 1170.5882 μV/K, and −65.7454 μV/K, respectively. At a temperature of 800 K, the p-type compound CuBr exhibits a maximum figure of merit (ZT) value of 0.6691, corresponding to a charge carrier concentration of 31.7926 × 1020 cm3. The CuCl and CuI compounds exhibit the maximum ZT values of 0.52043 and 0.5609, respectively. In order to achieve the desired results, it is necessary to decrease the charge carrier concentration in CuCl to n = 0.514 × 1022 cm−3 and increase the charge carrier concentration in CuI to n = 9.686 × 1022 cm−3; alternatively, the chemical potentials should be decreased by 0.2563 Ryd and 0.3974 Ryd, respectively.