Synergistic optimization on Seebeck coefficient and electrical conductivity in 2H-MoS2 enabled by progressively evolved stacking faults under high pressure and high temperature

Abstract

In thermoelectricity, the stacking faults (SFs) have been investigated mainly in phonon transport but rarely in carrier transport. For the layered thermoelectric materials, the layered nature makes them prone to SFs, especially under high pressure because of the induced shear stress between grains. Herein, we take the typical layered 2H-MoS2 as an example to investigate the effect of high-pressure in situ-induced SFs on the thermoelectric transport properties under high pressure and high temperature. It was found that a continuous transition of P-N-P type conductive behavior with increasing pressure was observed in the sign of Seebeck coefficient, finally leading to a not weakened Seebeck coefficient. Furthermore, the in situ-induced SFs enhanced the interlayer interaction and provided transport channels for carriers across the interlayers to boost the electrical conductivity to ∼11 100 S m−1 at 5.5 GPa, 1110 K. Consequently, combined with intrinsic ultralow thermal conductivity of MoS2, a maximum ZT value of 0.191 was obtained at 5.5 GPa, 1110 K, comparable to those doped/composited MoS2. This conduction-type transition induced synergistic optimization on Seebeck coefficient and electrical conductivity could be ascribed to that SFs, which had a progressive evolution process for stabilization with rising pressure, in which some associated defects might be induced, and the band structure could be modified for regulating the carrier distributions and the density of states around the Fermi level. This study provided profound insights of regulating conduction type via dynamically modulating the lattice defects for designing a high-efficiency TE device.