Ordered Architectonics of Magnetic Units Triggering Excellent Electrothermal Conversion Performance of Thick Films

The low electrical transport performance of flexible thermoelectric (TE) films is the bottleneck that restricts the development of in-plane heat dissipation technology based on the Peltier effect. The architectonics of magnetic units in TE materials have been proven to be an effective method to improve the efficiency of TE conversion. In this study, a series of Bi 0.5 Sb 1.5 Te 3 (BST)/Fe/BST thermoelectromagnetic (TEM) films were successfully prepared by ordered architectonics of ferromagnetic Fe nanoparticles (Fe-NPs) as magnetic units with different distribution shapes between two layers of BST/epoxy films through screen-printing combined with hot-pressing curing. The study focused on the effects of the architectonic shapes of Fe magnetic units on the microstructure and electrothermal transport properties of TEM films. The ordered architectonics of magnetic units could optimize the carrier transport pathways and reduce carrier scattering due to the altered carrier trajectories induced by the magnetic field generated by the Fe magnetic unit, which has been confirmed by the magnetoresistance test, thus effectively enhancing σ. The introduction of the Fe magnetic unit preserved a large α through magnetic scattering and spin entropy contributions. The TEM film with Fe magnetic units patterned as rhombic shapes (BST-RhoFe-BST film) realized a 36.5% enhancement in the maximum power factor (PF), attributing to the largest negative magnetoresistance. The cooling temperature difference of the single-leg film device fabricated by the BST-RhoFe-BST film reached 1.8 K, 125% higher than that of the device fabricated by the BST-BST film. Furthermore, the cascade device based on the TEM film realized a temperature drop of 2.8 K and exhibited excellent in-plane heat dissipation capability. This work reveals that the ordered architectonic shapes of magnetic units could effectively regulate the electrothermal conversion performance of TE films, and the magnetoresistance theory can reveal the scattering mechanism of charge carriers in TEM films.