Synergetic Evolution of Sacrificial Bonds and Strain-Induced Defects Facilitating Large Deformation of the Bi2Te3 Semiconductor

Bismuth telluride (Bi2Te3)-based semiconductors are one of the typical inorganic thermoelectric (TE) materials with excellent energy conversion efficiency, but the intrinsic brittleness severely limits their mechanical performance for further application with long-term reliability and in wearable devices. To understand the recent mechanical improvement of ductile and flexible inorganic TE materials at the atomic scale, here, we use molecular dynamics simulations to intuitively illuminate the enhanced shear deformability and performance stability of the brittle Bi2Te3 crystal through the tailored effects of surfaces. We reveal that the peculiar microbehavior originates from the layered hierarchical bonding structure with weak but reversible van der Waals force, namely, a sacrificial bond (SB), between Te1-Te1 adjacent layers. The synergetic evolution of local structures including SBs and strain-induced defects tends to partly compensate for the mechanical degradation caused by structure softening during shearing, achieving a relatively large strain before cleavage. The inspired engineering strategy of synergistically optimizing bonds and defects opens a pathway for designing multiscale hierarchical inorganic TE materials with excellent overall performance.