Superior flexibility merges high power density in single-crystal Bi2Te3 film thermoelectric generators.

Developing high-performance, mechanically robust power sources is critical for wearable microelectronic networks. Flexible thermoelectric technology offers a promising solution, but the central challenge remains the synergistic optimization of mechanical flexibility and functional performance in high-efficiency materials. Here, we report an antisite defect suppression strategy to resolve these conflicting demands in Bi2Te3 single-crystal thin films. By utilizing Se alloying, we tailor interplanar energetics to improve yield strength while enabling an unusual microcrack propagation mechanism that retains superior plasticity. This defect engineering approach also optimizes carrier mobility, leading to ultrahigh power factors of 50.6 for n-type and 48.2 μW cm-1 K-2 for p-type single-crystal films. A flexible thermoelectric generator fabricated from these films demonstrates robust bendability over 10,000 cycles and achieves a record power density of 805.0 W m-2 under a temperature difference of 79.6 K in natural cooling conditions. This study highlights intrinsic defect engineering's transformative potential for next-generation durable, high-power flexible thermoelectric generators.