Anisotropy engineering in solution-derived nanostructured Bi2Te3 thin films for high-performance flexible thermoelectric devices

Flexible thermoelectric (TE) technology can convert human-body heat into electricity, showing great promise for powering wearable devices. Achieving simultaneous excellent flexibility and high TE performance is still a big challenge for both inorganic and organic-based flexible TE materials. Here, to overcome this challenge in the well-known Bi2Te3-based materials, we propose an anisotropy engineering strategy triggered by nanostructuring design and excess Te addition. A two-step solution-synthesis method is developed to prepare patchwork-like Bi(2)Te(2.7)Se(0.)3 nanorods, which can be assembled into flexible thin films by the screen-printing and spark-plasma-sintering process. Owing to the weakened anisotropy by nanostructuring, our nanorods-derived Bi2Te2.7Se0.3 thin films exhibit excellent bending flexibility. Further introducing excess Te can optimize the anisotropy as well as the interfacial connecting and oxidation resistance of these thin films. Consequently, a high power factor of similar to 745 mu Wm(-1)K(-2) at room temperature can be achieved in the n-type Bi2Te2.7Se0.3 thin film with 10 % excess Te. These n-type thin films are further assembled with p-type legs (Bi0.5Sb1.5Te3 with 4 % excess Te) into a 5-pair TE device with good flexibility and stability, showing a maximum power density of similar to 6.06 Wm(-2) at a temperature difference of similar to 28.3 K. This work indicates that anisotropy engineering in solution-derived nanostructured thin films can be a facile way to balance the flexibility and TE properties, further advancing flexible TE devices.

Automated summary

Flexible thermoelectric technology has the potential to convert human body heat into electricity for wearable devices. However, achieving both high flexibility and performance remains a challenge. In this study, an anisotropy engineering strategy using nanostructuring and excess Te addition was proposed to overcome this challenge. Patchwork-like Bi(2)Te(2.7)Se(0.)3 nanorods were prepared using a two-step solution-synthesis method and assembled into flexible thin films. By optimizing the anisotropy and interfacial properties, a high power factor and power density were achieved in the TE devices. This research demonstrates the potential of anisotropy engineering in advancing flexible thermoelectric devices.