Interface Engineering Boosting High Power Density and Conversion Efficiency in Mg₂Sn_0.75Ge_0.25‐Based Thermoelectric Devices

Abstract Electrode contact interfaces for practical thermoelectric (TE) devices require high bonding strength, low specific resistivity, and superb stability. Herein, the state‐of‐the‐art Cu 2 MgFe/Mg Sn 0.75 Ge 0.25 interface is designed Mg ‐based TE devices, adhering to general strategy of propensity, thermal expansion matching, diffusion passivation, dopant inactivation. The interfacial stability verified by in situ transmission electron microscopy analysis, thereby confirming contributions from decreasing chemical potential gradient increasing activation energy barrier. single‐leg device exhibits a power density ( ω max ) 2.6 W cm −2 conversion efficiency η 8% under temperature difference (Δ T 370 °C, which record‐breaking value comparison other (Si, Ge, Sn)‐based devices. Additionally, two‐couple with p ‐type Bi Te 3 shows an excellent 1.3 5.4% Δ 270 comparable commercial proposed design provides technique constructing high‐performance using cutting‐edge materials.