Exceptional thermoelectric performance of a “star-like” SnSe nanotube with ultra-low thermal conductivity and a high power factor
Efficient thermoelectric energy conversion is both crucial and challenging, and requires new material candidates by design. From first principles simulations, we identify that a “star-like” SnSe nanotube – with alternating dense and loose rings along the tube direction – gives rise to an ultra-low lattice thermal conductivity, 0.18 W m−1 K−1 at 750 K, and a large Seebeck coefficient, compared with single crystal SnSe. The power factor of the p-type SnSe nanotube reaches its maximum value of 235 μW cm−1 K−2 at a moderate doping level of around 1020–1021 cm−3. The p-type nanotube shows better thermoelectric properties than the n-type one. The phonon anharmonic scattering rate of the SnSe nanotube is larger than that of the SnSe crystal. All of these factors lead to an exceptional figure-of-merit (ZT) value of 3.5–4.6 under the optimal conditions, compared to 0.6–2.6 for crystalline SnSe. Such a large ZT value should lead to a six-fold increase in the energy conversion efficiency to about 30%.