Interfacial Architecture Design for Efficient Carrier‐Phonon Decoupling in n‐Type GeSe

ABSTRACT Achieving practical thermoelectric applications requires matching pairs of high‐performance n ‐type and p ‐type materials from the same system to ensure reliability. However, in the eco‐friendly GeSe system, n ‐type performance has lagged behind its p ‐type counterpart due to strong carrier‐phonon coupling. Here, we demonstrate that an interfacial architecture design can effectively decouple carrier‐phonon transport in n ‐type GeSe‐based materials. This design promotes high‐entropy‐driven grain growth and the formation of sub‐grain boundaries, which reduce carrier scattering and yield an exceptional power factor of 4.5 µW cm −1 K − 2 . Meanwhile, stacking faults and Bi heavy doping areas, as well as dense point defects, can result in full‐spectrum phonon scattering and an ultra‐low lattice thermal conductivity of 0.37 W m −1 K −1 . These synergistic effects produce a record‐high figure of merit of 0.5 in Ge 0.48 Bi 0.17 Pb 0.35 Se 0.65 Te 0.35 at 723 K. Furthermore, we fabricated an all‐GeSe‐based π ‐type module that achieves a maximum conversion efficiency of ∼4.6% at the temperature difference of 350 K, demonstrating a significant breakthrough for all‐GeSe‐based π ‐type devices. This work illustrates high‐performance n ‐type GeSe can be achieved by interfacial architecture design, and further demonstrates the application potential of eco‐friendly GeSe‐based thermoelectric materials for mid‐temperature power generation.