Transport Properties and High Thermopower of SnSe2: A Full Ab-Initio Investigation

Motivated by the observation that many known layered chalcogenides show promising thermoelectric properties, we investigate the similar properties of SnSe2 by solving the Boltzmann transport equation for both lattice and electron. A self-consistent single parabolic band model (SPB) is employed to compute the electron relaxation time rigorously. The obtained intrinsic lattice thermal conductivities in a and c directions are 6.78 and 0.79 W/m·K at 300 K. The results show that acoustic phonon branches play the dominant role in heat transport. Thermoelectric properties of n-type SnSe2 are found to be significantly better than those of p-type doping for temperatures between 200 and 800 K and carrier concentrations between 1017 and 1020 cm–3. At n = 1020 cm–3 and 300 K, we find σa = 4.97 × 105 Ω–1·m–1 and σc = 3.39 × 104 Ω–1·m–1 and the ratio σa/σc = 14.67 for n-type SnSe2. Both electrical and lattice thermal conductivities show a strong anisotropic feature. A high thermoelectric figure of merit is revealed in n-type SnSe2 (ZTa = 2.95 and ZTc = 0.68 at n = 1020 cm–3 and 800 K). The large ZT value indicates that SnSe2 is a promising candidate for thermoelectric applications.