Electronic structure, optical and thermoelectric properties of cadmium chalcogenides monolayers

Abstract

Multifunctional low dimensional materials have been subjects of extensive investigations because of their unique physical and chemical properties. In this paper, we report a detailed analysis estimating the electronic structure, optical and thermoelectric properties of the cadmium chalcogenides CdX (X = S, Se and Te) monolayers using first-principles calculations. Results show that the CdS single layer is a direct gap semiconductor, while CdSe and CdTe monolayers have indirect band gap. As a function of the chalcogenide the band gap decreases from CdS to CdTe as a consequence of the s–p interaction. The CdX monolayers dielectric function and optical absorption coefficient are computed in a wide energy range up to 20 eV. All three single layers appear to be promising materials for optoelectronic applications provided that they have wide absorption band from visible to ultraviolet regime with large absorption coefficient up to 75.928, 70.355 and 71.193 (104/cm) for CdS, CdSe and CdTe monolayers, respectively. Finally, the CdX monolayers thermoelectric properties are calculated and analyzed as a function of temperature up to 1200 K. The single layers at hand show good thermoelectric performance provided that they exhibit large figure of merit. Interestingly, the CdTe monolayer exhibits a figure of merit larger than unity for temperatures up to 500 K. We believe that results reported here may be useful for designing practical applications of the cadmium chalcogenides monolayers.