Novel Thermal Diffusion Temperature Engineering Leading to High Thermoelectric Performance in Bi ₂Te ₃‐Based Flexible Thin‐Films

Abstract

Flexible Bi ₂Te ₃‐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 Bi ₂Te ₃ flexible thin films significantly limits their wide application. In this study, a novel thermal diffusion method is employed to fabricate n‐type Te‐embedded Bi ₂Te ₃ 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 Bi ₂Te ₃/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 cm ² 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 Bi ₂Te ₃ flexible thin films prepared at the diffusion temperature of 623 K. A thermoelectric sensor is also assembled through integrating the n‐type Bi ₂Te ₃ flexible thin films with p‐type Sb ₂Te ₃ counterparts, which can fast reflect finger‐touch status and demonstrate the applicability of as‐prepared Te‐embedded Bi ₂Te ₃ flexible thin films. This study indicates that the thermal diffusion method is an effective way to fabricate high‐performance and applicable flexible Te‐embedded Bi ₂Te ₃‐based thin films.

Abstract

In this study, flexible n‐type Bi ₂Te ₃‐based thin‐films are successfully prepared through facile thermal diffusion method and further induce Te/Bi ₂Te ₃ heterojunctions and energy filtering effect at the Te/Bi ₂Te ₃ interfaces to optimize the thermoelectric performance through tuning the diffusion temperature.