Synergistic modulation of SLME and thermal transport toward promising p-type lead-free halide semiconductors In2TiX6 (X = Br, I) via first principles analysis

Abstract

Lead halide perovskites have been replaced by the environmentally acceptable and effective lead-free double perovskite material. Double perovskites are innovative compounds for sustainable energy and budding substitutes to organic as well as lead-based solar cells. In the current study, it has been expounded on the structural, electronic, thermoelectric, as well as thermodynamic characteristics of newly designed double perovskites In₂TiX₆ (X = Br, I) by means of ab-initio computations relied on the FP-LAPW tactics and semi-classical Boltzmann transport theory with PBE-GGA as exchange correlation potential. To obtain accurate value of band gaps (1.294 eV and 1.025 eV), TB-mBJ approximation has been used along with PBE-GGA. The best combinations of both compounds have spectroscopic limited maximum efficiency (SLME) values 33.96% and 31.63%, that are appropriate for solar cell absorbers, at 300 K, respectively. We have also computed Debye temperature $\left({\theta }_D\right)$ and Grüneisen parameter $\left(\gamma \right)$ to find the lattice thermal conductivity for both the investigated alloys. Thermoelectric properties have been labeled by Seebeck coefficient, electrical as well as thermal conductivities, and figure of merit. The peak values of Seebeck coefficient of 248 μV/K and 202 μV/K are observed for In₂TiBr₆ and In₂TiI₆ respectively in the p-type regions. Attained results illustrates that the investigated In₂TiX₆ may be contender in thermoelectric due to their high figure of merit in low as moderate temperatures. Our results suggest that these materials are viable for use in thermoelectric devices.