Theoretical Prediction and Thermal Transport Properties of Novel Monolayer TlPt₂Se₃

The theoretical prediction, electronic properties, and thermal transport properties of novel monolayer TlPt₂Se₃ are investigated using the first-principles calculations and semi-classical Boltzmann transport theory. The calculated phonon band structure and exfoliation energy confirm that monolayer TlPt₂Se₃ is a stable material and can be exfoliated from its bulk counterpart. The exfoliation energy of the monolayer turns out to be 37 meV Å⁻², comparable with the exfoliation energy of monolayer PdSe₂. The HSE06 indirect bandgap of monolayer (bulk) TlPt₂Se₃ amounts to 1.18 eV (0.63 eV). The relaxation time is calculated considering three types of scattering mechanisms. The monolayer outperforms the bulk counterpart in the Seebeck coefficient and power factor for both p-type and n-type dopings. Monolayer TlPt₂Se₃ shows a high p-type Seebeck coefficient of 211 µV K⁻¹ compared to the n-type Seebeck coefficient of 103 µV K⁻¹ at maximum considered temperature (600 K) and a carrier concentration (10²⁰ cm⁻³). The calculated lattice thermal conductivity of monolayer TlPt₂Se₃ is 1.92 W m⁻¹ K⁻¹ at 600 K which is lower than the monolayer PtSe₂ and MoSe₂. The p-type figure of merit of 0.64 (at 600 K) affirms that the monolayer TlPt₂Se₃ is an excellent thermoelectric material.