Two-Dimensional SnSe Composited with One-Dimensional Mn Nanowires: A Promising Thermoelectric with Ultrahigh Power Factor

Two-dimensional (2D) SnSe is a promising candidate for thermoelectric applications. In this work, we have explored an optimization strategy for thermoelectric conversion in two-dimensional monolayer SnSe by compositing with one-dimensional (1D) Mn nanowires. The thermoelectric properties were investigated using the first-principles theory calculation combined with the Boltzmann transport theory. The proposed 2D-1D composite structure can regulate the band gap and the degeneracy by changing the distance between 1D Mn nanowires. It was found that the carrier mobility can be increased to a maximum of 8143.26 cm2 V-1 s-1 at 300 K due to the reduced electron-phonon scattering effect. In addition, high band degeneracy and high carrier mobility lead to an ultrahigh power factor of 200 μW cm-1 K-2 in 3Mn-SnSe at 300 K, which can compensate for the negative effect of high electronic thermal conductivity. As a result, record high ZT values from 0.73 at 200 K to 3.78 at 650 K are achieved in 3Mn-SnSe, 39.2% larger than the ZT values of the pristine monolayer SnSe on average. This work presents an effective structural modification strategy to optimize the thermoelectric performance of 2D SnSe, with the potential of extension to other low-dimensional thermoelectric materials.