Abstract
Bismuth telluride (Bi_2Te_3)-based thermoelectrics have emerged as prime candidates for wearable and low-grade heat harvesting. However, the brittleness and insufficient mechanical strength lead to unsatisfactory machinability and flexibility. Here, this study demonstrates grain size- dependent strengthening-to-softening transition in Bi_2Te_3 thin films, achieving a maximum strength of 363 MPa, several times greater than single-crystal bulk counterparts. Remarkably, a novel energy dissipation mechanism mediated by stacking faults-induced ripplocation structures enables an unprecedented tensile ductility of ≈7.3%. High-density stacking faults simultaneously suppress the dominant grain boundary scattering on carrier transport, preserving excellent thermoelectric performance (power factor ≈2760 μW m~(-1) K~(-2) at 550 K). The fabricated Bi_2Te_3-based thin-film devices exhibit superior flexibility (over 10 000 bending cycles), power output, and stability across room-to-medium temperatures. This work establishes a novel microstructural design paradigm for next-generation flexible thermoelectric devices with superior strength-ductility synergy and thermoelectric performance.
NETL
NSTL
Wiley