Enhancing Thermoelectric Performance in L-DED-Printed p-Type Bi2Te3 by Synergistic Lattice Planarization and Defect Engineering.

While laser 3D printing offers unique advantages for fabricating complex architectures, its broader application is hindered by the stringent requirements for high-quality powder precursors and the inferior thermoelectric properties of the printed bulk materials. Herein, irregularly shaped p-type Bi0.5Sb1.5Te3 powders were successfully printed into polycrystalline bulks using the laser-directed energy deposition (L-DED) method via the optimization of printing parameters. The incorporation of excess Te and Sb atoms not only facilitates lattice plainification to enhance carrier transport, but also unexpectedly intensifies phonon scattering via the in situ formation of multiple defects. This synergistic enhancement enables the printed p-type bulks to reach a remarkable zT of 1.42 at 317 K. We assembled a 127-pair thermoelectric device using L-DED-fabricated p-type Bi0.5Sb1.5Te3 and SLM-fabricated n-type Bi2Te2.7Se0.3, which achieved an experimental efficiency of ∼5.6% at a temperature difference of 200 K. The findings of this work lay an important foundation for the application of emerging laser-based 3D printing technologies in the field of thermoelectrics.