Flexible Bi₂ Te₃ -based thermoelectric devices can function as power generators for powering wearable electronics or chip-sensors for internet-of-things. However, the unsatisfied performance of n-type Bi₂ Te₃ flexible thin films significantly limits their wide application. In this study, a novel thermal diffusion method is employed to fabricate n-type Te-embedded Bi₂ Te₃ flexible thin films on flexible polyimide substrates, where Te embeddings can be achieved by tuning the thermal diffusion temperature and correspondingly result in an energy filtering effect at the Bi₂ Te₃ /Te interfaces. The energy filtering effect can lead to a high Seebeck coefficient ≈160 µV K^-1 as well as high carrier mobility of ≈200 cm² V^-1 s^-1 at room-temperature. Consequently, an ultrahigh room-temperature power factor of 14.65 µW cm^-1 K^-2 can be observed in the Te-embedded Bi₂ Te₃ flexible thin films prepared at the diffusion temperature of 623 K. A thermoelectric sensor is also assembled through integrating the n-type Bi₂ Te₃ flexible thin films with p-type Sb₂ Te₃ counterparts, which can fast reflect finger-touch status and demonstrate the applicability of as-prepared Te-embedded Bi₂ Te₃ flexible thin films. This study indicates that the thermal diffusion method is an effective way to fabricate high-performance and applicable flexible Te-embedded Bi₂ Te₃ -based thin films.

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