Introducing atomistic dynamics at van der Waals surfaces for enhancing the thermoelectric performance of layered Bi0.4Sb1.6Te3†

Abstract

Thermoelectrics (TEs) enable the direct conversion of heat into electricity, but the thermoelectric performance of the state-of-the-art layered materials has been limited owing to the restricted approaches available for decoupling the carrier and phonon transport. Herein, a unique and novel feature of the intralayer van der Waals bonds/interactions is explored for improving the structural evolution and transport properties of a layered TE material. The atomistic dynamics governing inversion in van der Waals layers/bonds is established as an innovative material engineering paradigm. We selected the layered state-of-the-art Bi_0.4Sb_1.6Te₃ material as a representative prototype to identify the transformative role of the intralayer in realizing high TE performance. The induced atomic diffusion at the van der Waals layers and prevailed crystal-amorphicity duality optimized the electronic and chemical environments with an elevated carrier concentration and maintained the Seebeck coefficient, which led to an improved power factor of ≈49 μW cm⁻¹ K⁻². Besides, the atomistic surface reconstruction/defects caused a reduction in the thermal conductivity to ≈0.97 W m⁻¹ K⁻¹, which led to an ultra-high figure of merit (ZT_max) of ≈1.54 at ∼373 K. Thus, the present work provides a generic and practical strategy via the unique doping-dependent atomistic engineering, which can also be implemented in other layered structures to tailor the TE properties.