Two dimensional chalcogenides as promising materials for thermoelectric applications

Abstract

Increasing energy demands of the present world and the severe environmental problems has motivated researchers to develop green energy conversion technologies. Recently, thermoelectricity has gained much attention from the scientific community as it can directly convert the waste heat into electrical energy and causes no environmental harms. Thermoelectric devices have a variety of applications in power generation, refrigeration and waste heat recovery. However, the presently available thermoelectric materials are toxic (e.g. PbTe) and their cost is quite high. Thus, the search for new thermoelectric materials which are non-toxic, have low cost and also have high conversion efficiency is greatly demanded. This thesis aims at designing economically efficient thermoelectric materials for power generation applications. For this purpose, we have investigated the thermoelectric properties of two-dimensional (2D) chalcogenides. First, we studied the transport properties of the SnSe bilayer. The ultralow lattice thermal conductivity of the bilayer (0.90 Wmand#8722;1Kand#8722;1 at 300 K) and high figure of merit (ZT) values of the bilayer make it suitable for thermoelectric applications. Next, we investigate the vacancies effect on the thermoelectric properties of SnSe monolayer. The power factor of monolayer is found to decrease with the presence of vacancies in the lattice. Next, we studied the thermoelectric properties of bulk and few-layer SnS. These 2D SnS materials have exceptionally high charge carrier mobilities and low lattice thermal conductivities. As a result, their calculated ZT values are quite high. Last, we studied the effect of isotropic strain on the thermoelectric properties of the SnS bilayer which has resulted in enhancement of thermoelectric performance of the bilayer. Thus strain-engineering can be used as an effective method for tailoring the thermoelectric properties of the materials. Altogether, the results of this thesis highlight the potential of 2D tin chalcogenides for thermoelectric applications.