First-principles investigations of metal chalcogenides Tl2Hg3X4(X=S,Se,Te) for advanced optoelectronic and thermoelectric applications

Abstract

The crystalline metal chalcogenides materials have got great attraction due to their narrow bandgap materials for renewable energy applications. In the present work, we have broadly explored the optoelectronic and thermoelectric properties of Tl2Hg3X4(X ​= ​S, Se, Te) using first-principle calculations. The Tl2Hg3S4, Tl2Hg3Se4, and Tl2Hg3Te4 have a monoclinic crystal structure and exhibit semiconducting nature with band gaps of 2.0 ​eV, 1.5 ​eV, and 0.8 ​eV, respectively. In the visible region, a minimum absorption occurred for the S dopant, but as we replace S with Se/Te a halted absorption is seen in the visible region that confirming their nominal employment in optoelectronic applications (solar cells). Optical absorption of Se and Te dopant in Tl2Hg3X4 is found in I.R and the visible region of the radiation, making them promising candidates for optoelectronics. Further, the thermoelectric parameters versus carrier concentration are studied for these materials using the BoltzTraP code. The drifts of thermoelectric parameters for the Te dopant diverge from the tendencies of S and Se dopants at specific temperatures i.e., at 300, 500, and 700 ​K. The power factor (PF) of Tl2Hg3S4 and Tl2Hg3Se4 (Tl2Hg3Te4) favor n-type (p-type) doping, indicating higher mobility of electrons(holes) as compared with the holes (electrons). These findings suggest the practical realization of these compounds for emerging optoelectronic and renewable energy device applications.