Negative-thermal-expansion particles enable high-performance and ultradurable thermoelectric modules

Interfacial compatibility across multiple material parts governs device stability in solid-state batteries, flexible electronics, and high-temperature fuel cells. For thermoelectric devices, researchers principally focused on chemical reactivity and mechanical properties of material components, whereas precise control of the coefficient of thermal expansion (CTE) remains elusive. Here, we propose an innovative strategy using negative-thermal-expansion (NTE) particles to regulate CTE and resolve interfacial incompatibility. Incorporating predesigned interface reaction–free NTE particles into Bi 2 Te 3 -based, Mg 3 Sb 2 -based, and PbTe-based materials effectively improves thermoelectric performance, alleviates thermal stress, and enhances interfacial stability across a broad temperature range (300 to 800 kelvin). Notably, the NTE-modified Mg 3 (Sb,Bi) 2 /Bi 0.4 Sb 1.6 Te 3 two-pair module achieves a record-high conversion efficiency (η) of 8.4% at Δ T = 350 K with a 71% interfacial thermal stress reduction, maintaining a stable interface and unchanged η throughout 1000-hour (42 days) thermal cycling. Our strategy establishes a universal approach for improving interfacial compatibility in high-temperature functional modules including thermal-barrier coatings and solar thermophotovoltaic devices.