High thermoelectric performance induced by quasi-one-dimensional structure in X(Cs & Rb)₂PtTe₂

In the era of encouraging green and sustainable energy, thermoelectric (TE) materials play a crucial role in directly converting heat energy into electrical energy. This study reports on a promising quasi-one-dimensional TE material, X(Cs & Rb)₂PtTe₂, which simultaneously achieves ultralow lattice thermal conductivity (κ_L) and a high power factor. Using first-principles calculations, anharmonic lattice dynamics, self-consistent phonon theory, and the Boltzmann equation, we systematically investigated the structural stability and TE transport properties of X(Cs & Rb)₂PtTe₂. Due to the confinement effects induced by reduced dimensionality, with quartic anharmonicity corrections, at 300 K, the κ_L values of Cs₂PtTe₂ and Rb₂PtTe₂ in the directions perpendicular to the Pt-Te chains are only 0.14 and 0.12 W m^-1 K^-1, making them excellent thermal insulators. Additionally, their band structures exhibit "pudding-mold type" characteristics, resulting in high Seebeck coefficients and power factors. At room temperature, the optimal TE figure of merit (ZT) for n-type doped Cs₂PtTe₂ and Rb₂PtTe₂ in the directions perpendicular to the Pt-Te chains is 1.12 and 1.68, respectively. At 800 K, the ZT values for n-type doped Cs₂PtTe₂ and Rb₂PtTe₂ reach 4.13 and 5.52. Their TE conversion efficiency significantly surpasses that of traditional TE materials, making them competitive with other transducer devices and demonstrating substantial commercial potential.