Decoupling Electron and Phonon Transport in 3D‐Printed Bismuth Telluride via Synergistic Compositional Co‐Enrichment

ABSTRACT Decoupling electronic and phononic transport requires nanoscale control over scattering landscapes. Here, we show that direct ink writing generates a hierarchical nanoarchitecture in Bi 2 Te 3 , which comprises nanopores (10‐150 nm), amorphous‐crystalline nanointerfaces, and dense grain boundary networks that suppress lattice thermal conductivity by around 50% from ∼0.6 W m −1 K −1 to ∼0.3 W m −1 K −1 , as quantitatively confirmed by Debye‐Callaway modeling. Sb/Te/Se co‐enrichment (Sb/Te co‐enrichment was applied to the p ‐type BST system, while Te/Se co‐enrichment was applied to the n ‐type BTS system) refines this nanopore distribution while driving atomic‐scale intercalation of Sb/Te enrichment between quintuple layers, as directly visualized by atomic‐resolution STEM‐EDS, bridging van der Waals gaps to selectively restore electrical conductivity without compromising phonon scattering. The optimized p ‐type and n ‐type materials achieve peak ZT values of 0.87 (303 K) and 0.89 (423 K), respectively, which exceed commercial Bi 2 Te 3 performance. Single‐leg generators deliver conversion efficiencies of 3.51% and 2.53%, ranking among the highest for additively manufactured thermoelectrics. This work demonstrates that process‐generated nanoarchitectures, combined with atomic‐scale compositional engineering, enable effective phonon–electron decoupling in printed thermoelectric materials.