Enhancement of the power factor of SnSe by adjusting the crystal and energy band structures

Abstract

Adjusting the crystal and band structures is of great significance for phonon or carrier transport in functional materials. Lattice contraction was designed to adjust the crystal and energy band structures, which bring about energy valley degeneracy and a band gap decrease in the SnSe system. The Seebeck coefficient of the rapid cooling sample increases significantly due to the energy valley degeneracy. The multichannel effect based on the energy valley degeneracy weakens scattering among the carriers and maintains a high σ along the “⊥” direction. The PF for the rapid cooling sample at 773 K reaches 686 μW m⁻¹ K⁻², which is boosted by 66.13% compared with that of the slow cooling sample. Due to the contribution from the high power factor, the ZT value of the rapid cooling sample reaches 0.86, which is an increase of 26% compared with the 0.69 of the slow cooling sample.