OICC Press International Journal of Nano Dimension 2228-5059 16 1 2025 01 10 First-principles calculations to investigate electronic, optical and thermoelectrical performances of Pb/Te-based nanolayer and bulk chalcogenides 1 12 10.57647/j.ijnd.2025.1601.01 EN Khadijeh Rajabi Department of Physics, Faculty of Basic Science, Qom Branch, Islamic Azad University, Qom, Iran https://orcid.org/0009-0007-1897-4363 Hasan Tashakori Department of Physics, Faculty of Basic Science, Qom Branch, Islamic Azad University, Qom, Iran https://orcid.org/0000-0002-4545-2727 Esmaeil Pakizeh Faculty of Gas and Petroleum, Yasouj University, Gachsaran, Iran https://orcid.org/0000-0003-3378-7826 Fataneh Taghizadeh-Farahmand Department of Physics, Faculty of Basic Science, Qom Branch, Islamic Azad University, Qom, Iran https://orcid.org/0000-0002-8807-9707 Journal Article 2025 01 10 The electronic,thermoelectricand optical properties of  bulk and nanolayers chalcogenides, specifically XTe (X = Si, Ge, Sn, and Pb) and PbY (Y = O, S, Se, and Te), have been investigated using density functional theory (DFT) with the GGA-PBE functional and semiclassical Boltzmann theory via Quantum ESPRESSO and BoltzTraP codes. The results of the electronic band structure analysis indicate that compounds such as PbO, PbS, PbSe, PbTe and GeTe exhibit direct band gaps, making them suitable for semiconductor applications. On the other hand, SiTe and SnTe compounds exhibit metallic behavior. Also, the GeTe bulk was converted from semiconducting to conducting in the nanolayer structure. The thermoelectric properties of these bulk and nanolayerschalcogenides, including electrical conductivity, electronic thermal conductivity, and Seebeck coefficient, have been calculated. It was observed that the Seebeck coefficient decreases with increasing temperature in all semiconductor samples. Moreover, the thermal and electrical conductivity coefficients increase with the increase in chemical potential, transferring it to the electrons in the conduction layer. Based on the findings, it can be concluded that PbTe shows promising potential as a candidate material for thermoelectric devices. Seebeck coefficient in PbO, PbS, and PbSe nanolayers increased compared to the bulk structure. The optical properties, including the real and imaginary parts of the dielectric function, absorption, and reflectivity as a function of energy, have also been calculated. The absorption edges of the bulk chalcogenides extend into the visible spectrum due to their suitable bandgap values. Additionally, these materials exhibit non-transparency in certain regions of the electromagnetic spectrum, making them suitable for use as absorbent materials. Among the chalcogenides studied, PbS shows promising potential for optoelectric industries due to its low refractive index and high optical gap. Also, the decrease in the refractive index of the nanolayers compared to the bulk shows more optical absorption in them. Additionally, among bulks compounds, PbTe shows promising potential for thermoelectric applications, while among nanolayers, PbO is the most suitable material.