The staggered-layer induced elasticity strengthening mechanism in flexible Bi2Te3

Wearable flexible devices require the development of thermoelectric (TE) materials with high strength, excellent elastic bendability, and superior ductility. Here we report a staggered-layer strategy that overcomes the strength-flexibility dilemma. Our findings indicate that the newly formed strong Bi–Bi covalent bond between the staggered layer leads to an average 40% increase in the bond energy of the van der Waals Te–Te bond. A large Poisson’s ratio leads to a high maximum linear elastic strain (${\epsilon }_E^{\mathit{max}}$${\epsilon }_E^{\mathit{max}}$), enhancing shear strength by 83.3%, which is consistent with a 92.2% increase in micro-pillar compressive strength. The narrow stiffness gap and bond energy gap facilitate the coordinated deformation that maintains sustained linear elasticity during compression. Moreover, the low BFCs of the Te–Te and Te–Bi bonds (0.72 eV/Ų and 3.85 eV/Ų) contribute to the experimentally observed bending flexibility. This staggered-layer-induced elasticity strengthening mechanism offers a promising strategy for the rational design of highly reliable wearable TE devices.