A Comprehensive DFT Insight on Thermoelectric Response of Halide Perovskites TlGeZ3 (Z = Cl, Br and I) for Renewable Energy Devices

The diverse perovskites are considered innovative solids for optoelectronic devices and photovoltaic cells. We investigated the structural, electrical, phonon dispersion, mechanical, optical, as well as transport properties of TlGeZ₃ (Z = Cl, Br, I) using calculations based on density functional theory (DFT). A phonon dispersion shows the examined materials' structural stability and formation energy of the TlGeZ₃ (Z = Cl, Br, I) compound, whilst positive phonon dispersion frequencies and elastic constants supported thermal and mechanical stability. In addition, the brittle and ductile behavior of the Poisson and Pugh ratios are investigated. The mechanical investigation has also documented the Debye and melting temperatures. The bandgap is tuned from 2.43 eV, 0.94 eV, and 0.57 eV with a modified Becke Johnson (mBJ) approximation by replacing Cl with Br and I. The optical spectrum reveals a transition \({\varepsilon }_{1}(0)\) (3.19, 6.10, 8.99) from the ultraviolet to the absorption spectrum area. The refractive index for each compound (TlGeZ₃ (Z = Cl, Br, I)) is (1.87, 2.51, 3.01) respectively. Additionally, the study's affinity for solar cells and optoelectronic uses is promised by the low light reflection (0.99, 0.18, 0.25) and optical energy loss range (1.9–3.1 eV) in the visible region. The thermal characteristic reveals the thermal stability, and the figure of merits values 0.9–1 advocate that the perovskite materials are suitable for use in thermal devices.