Study of optoelectronic and thermoelectric properties of double perovskites X₂HfI₆ (X = Ga, In, Tl) for renewable energy

Abstract

The double perovskites (DPs) are outstanding materials for renewable energy and other optoelectronic applications. Here in this paper, the thermoelectric and optical behavior of X2HfI6 (X = Ga, In, Tl) have been explained systematically by DFT. The structural stability has been certified using ionic radii in terms of tolerance factor, and dynamic stability has been confirmed by positive phonon dispersion frequencies in acoustic modes. The band structure findings show the direct band gaps for (Ga, In, Tl) based DPs. The optical properties have been investigated by dispersion, absorption, refection, and related other optical characteristics. The absorption bands are existing in ultraviolet region and shifted to higher energy (blue shift). The reflection and optical loss of light are noted less than 0.3 which increases their potential for optoelectronic devices. The high Seebeck coefficient and electrical conductivity along with ultralow lattice thermal conductivity confirm the high figure of merit at and below the room temperature.

DFT combined to Boltzmann transport theory for optoelectronic and thermoelectric properties investigations for Se (4 & 8 (at.%)) doped Li2SnS3

“…In the case of pure Li 2 SnS 3 , the highest point of the valence band (VBM) is situated between the X and M points, while the lowest point of the conduction band (CBM) is found at M. This configuration results in direct band gap for parental and 4% doping of Se atom while increasing the doping concentration of Se (8%) changes the nature from direct to indirect band gap of 2.18 eV in Li 2 SnS 3 , which aligns well with previous theoretical calculations and an experimental value of 2.38 eV [46]. Hence, these materials of the direct band gap nature, shows better photovoltaic possibility over the Se 8% [47][48][49][50][51].…”