Optimized hetero-interfaces by tuning 2D SnS2 thickness in Bi2Te2.7Se0.3/SnS2 nanocomposites to enhance thermoelectric performance

Tuning the electron and phonon transport properties of thermoelectric materials to partially decouple electrical conductivity, Seebeck coefficient and thermal conductivity is the core issue to improve the conversion efficiency. Herein, Bi2Te2.7Se0.3/SnS2 nanocomposites with a unique hetero-structure that the 2D atomically thin SnS2 nanosheets (2-15 nm) homogeneously assembled on BTS grain boundaries have been successfully synthesized to explore the size-dependent electron and phonon regulating effects. The atomically thin Bi2Te2.7Se0.3/SnS2 interfaces allow for effective phonon scattering and decreased thermal conductivity, while the energy filtering effect increase the power factor, resulting an improved figure of merit (ZT). By controlling the thickness of the interfaces SnS2 layers, simultaneously optimized the electron transporting and phonon scattering properties has been achieved, a high ZT = 0.93 at 450 K is obtained. The designed Bi2Te2.7Se0.3/SnS2 nanocomposites give us opportunities to systematically study the size-dependent electron tuning effect (energy filtering effect) and phonon scattering (classical size effect), which finally give rise to the enhancement of ZT.