Selective Interfacial Barriers Drive High‐Performance GeTe Thermoelectrics

ABSTRACT Thermoelectric technology provides a sustainable solution for harvesting waste heat. High‐efficiency waste heat recovery demands high figure of merit ( ZT ) materials, which are limited by intrinsic carrier and phonon coupling. Here, we introduce VSe ₂ nanowire precipitates to construct selective interfacial barriers for effective decoupling. Specifically, the electron transport is optimized by the synergistic effects of the minimization of the Fermi level mismatch between the VSe ₂ and GeTe, and a substantial reduction of interface state density via semi‐coherent interfaces. Concurrently, the significant phonon frequency mismatch at interfacial barriers effectively suppresses phonon transport. This approach yields a high ZT of 2.7 at 773 K, and record‐high average ZT of 1.9 across 300–773 K in the (Ge _0.82 Mn _0.04 Bi _0.04 Pb _0.1 Te) _0.99 (VSe ₂ ) _0.01 . The corresponding π‐type module exhibits a conversion efficiency of 11.4% under a 440 K temperature difference. This work highlights the potential of selective interfacial barriers for advancing thermoelectrics and energy‐harvesting applications.