Interfacial engineering of solution-processed Bi2Te3-based thermoelectric nanocomposites via graphene addition and liquid-phase-sintering process

Abstract

Solution-processed Bi2Te3-based nanocomposites usually have rich nanostructures and interfaces that show great promise for promoting the thermoelectric performance according to the theoretical effects of “quantum confinement” and “topological insulator”. Here, an interfacial engineering strategy is developed to enhance the thermoelectric performance of n-type Bi2Te3-based nanocomposites upon synergistically introducing liquid-phase-sintering (LPS) process and adding graphene oxide (GO). Enhanced phonon scatterings by interfacial GO and various nanograins lead to an ultralow lattice thermal conductivity of ∼ 0.21 Wm-1K−1 at 398 K for the 1 wt% GO-added Bi2Te2.5Se0.5. Excess Te activated LPS process can improve the interfacial connection for good electrical conductivity without increasing the lattice thermal conductivity. The excess Te and addition of GO can also suppress the donor-like effect in Bi2Te3 for optimizing the carrier concentration. Due to these synergetic effects, a peak figure of merit (ZT) of ∼ 1.03 at 473 K and an average ZT of ∼ 0.85 within 300–473 K can be achieved in the 1 wt% GO-added sample. A single-couple TE device is also made using our n-type 1 wt% GO-added Bi2Te2.5Se0.5 and the traditional p-type Bi0.5Sb1.5Te3, showing a maximum power density of ∼ 0.06 Wcm−2 at temperature difference of 154.8 K. Moreover, the difference between GO and nitrogen-doped graphene as additives is also systematically discussed, providing a guide for the rational use of graphene in interfacial design.