Flexible Bi₂Te₃‐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 Bi₂Te₃ flexible thin films significantly limits their wide application. In this study, a novel thermal diffusion method is employed to fabricate n‐type Te‐embedded Bi₂Te₃ 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 Bi₂Te₃/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 Bi₂Te₃ flexible thin films prepared at the diffusion temperature of 623 K. A thermoelectric sensor is also assembled through integrating the n‐type Bi₂Te₃ flexible thin films with p‐type Sb₂Te₃ counterparts, which can fast reflect finger‐touch status and demonstrate the applicability of as‐prepared Te‐embedded Bi₂Te₃ flexible thin films. This study indicates that the thermal diffusion method is an effective way to fabricate high‐performance and applicable flexible Te‐embedded Bi₂Te₃‐based thin films.

Through incorporation of isostructural Bi₂Te₃ nanoinclusions in n-type Bi₂Te_2.7Se_0.3 we achieve unprecedented energy-conversion efficiency η = 10.5% with record high ZT_max = 1.35.