Optoelectronic and thermoelectric properties of LiCuM (M=S, Se and Te) half-Heuslers: insights first principle calculations

Abstract

The work is performed to study the structural stability and optoelectronic prop-
erties as well as thermoelectric properties of LiCuM (M=S, Se and Te) half-Heusler
semiconductors using density functional theory (DFT) and semi-classical Boltzmann
transport. The ground state results show that the compounds exhibit semiconducting
behavior with a direct band-gap. The elastic parameters indicated that the present
compounds were mechanically, dynamically stable and brittle. The calculated optical
properties in GGA and GGA+U approaches show that the dominant response in the
low ultraviolet and visible energy regions. The thermoelectric properties are evaluated
using the Slack model and temperature dependent relaxation time in the temperature
range of 100K to 1000K. The response of thermoelectric properties with temperature
is evaluated and discussed in detail. The figure of merit with relaxation time is found
to increase with temperature and reaches the optimal values in GGA and GGA+U
at 1000K are 0.69(0.01), 0.66(0.665) and 0.67(0.778) for LiCuS, LiCuSe and LiCuTe,
respectively. The lattice thermal conductiv-
ity decreases with increasing temperature. These properties make these compounds
promising candidates for optoelectronic and thermoelectric devices.