First-principles calculations to investigate structural, electronic, thermoelectric, and optical properties of heavy thallium perovskite TlPbX3 (X = Cl, Br, I)

By dint of the Full potential linearized augmented plane wave (FP-LAPW) method employed in density functional theory (DFT) technique, the mechanical stability, electronic behaviour, optical response, and thermoelectric behaviour of Thallium based halide perovskites TlPbX3 (X = Cl, Br, I) have been theoretically investigated for the first time. The energy volume optimization curves, formation energy, and cohesive energy also confirm these perovskites' structural stability. The calculated value of lattice parameter a0 agrees well with available results. The electronic band structure plots, as well as density of states plots of these compounds, reveal their semi-conducting nature using Tran Blaha modified Becke Johnson approximation-generalized gradient approxima-tions (TB-mBJ-GGA) and (PBE-GGA) Perdew-Burke-Ernzerhof-generalized gradient approximation with wide band gaps for TlPbCl3 and TlPbBr3. The nature of chemical bonding in these compounds is discussed by the electron density plots. The optical constants such as the dielectric functions, refractive index, extinction coef-ficient, optical reflectivity, absorption coefficient, and transmittance are also calculated and discussed in detail. Furthermore, we examined the elastic and mechanical properties which ensure the mechanical stability of TlPbX3 (Cl, Br, I) respectively. The chemical potential, carrier concentration and, the temperature dependence of Seebeck coefficient, electrical conductivity, electrical, thermal conductivity, power factor, and figure of merit are investigated in detail using BoltzTrap code. Together these results lead an outlook on the future progress of thermoelectric halide perovskites to accentuate the augmentation of electronic performance, such as changing carrier concentration chemical potential optoelectronic devices and renewable energy harvesting technologies.