Manipulating Charge-Mechanical Coupling to Achieve Superior Ductility and High Thermoelectric Properties in Layered Bismuth Telluride.

Conventional thermoelectric semiconductors are intrinsically brittle, limiting their integration and reliability. Recent studies have revealed intrinsic plasticity in several systems, such as Mg3Bi2 and Bi2Te3, yet this deformability has been primarily attributed to mesoscopic dislocation activity. Here, we unveil an atomic-level charge-mechanical coupling that directly governs plastic deformation in layered bismuth telluride materials. It represents a dislocation-independent pathway for deformation, originating from the tunable interlayer bonding itself. We demonstrate that reducing carrier concentration weakens van der Waals attraction, expands interlayer spacing, and thus promotes interlayer slip, resulting in remarkable ductility with a bending strain of 26% and a compressive strain exceeding 90%. Importantly, this mechanism does not compromise thermoelectric performance. Instead, the optimized p-type Bi0.5Sb1.5Te3 simultaneously achieves a high peak dimensionless figure of merit (zT) of 1.23 at 350 K. This work reveals how electronic states can be harnessed to tune plasticity in layered semiconductors and provides a general strategy for synergistically enhancing mechanical flexibility and thermoelectric efficiency.