Two-Dimensional Tellurene as Excellent Thermoelectric Material

We study the thermoelectric properties of two-dimensional tellurene by first principles calculations and semiclassical Boltzmann transport theory. The HSE06 hybrid functional results in a moderate direct band gap of 1.48 eV at the Gamma point. A high room temperature Seebeck coefficient (S-xx = 0.38 mV/K, S-yy = 0.36 mV/K) is combined with anisotropic lattice thermal conductivity (kappa(1)(xx) = 0.43 W/m K, kappa(1)(yy) = 1.29 W/m K). Phonon band structures demonstrate a key role of optical phonons in the record low thermal conductivity that leads to excellent thermoelectric performance of tellurene. At room temperature and moderate hole doping of 1.2 X 10(-11) cm(-2), for example, a figure of merit of ZT(xx) = 0.8 is achieved.