Corrugating van der Waals gaps for decoupling heat and charge transport in layered thermoelectrics

Layered thermoelectric materials face intrinsic challenges in disentangling phonon and electron transport due to their anisotropic bonding networks. Here, we introduce a van der Waals gap engineering strategy that deliberately imposes out-of-plane stress on n-type bismuth telluride (Bi₂Te₃). Selective interlayer doping creates local charge imbalance, which in turn drives ripple-like lattice corrugations. These structural undulations mimic substrate-induced strain fields, renormalize phonon dispersion, and substantially reduce phonon velocity, thereby suppressing lattice thermal conductivity. The corrugation amplitude is far smaller than the electronic mean free path, ensuring negligible additional electron scattering. As a result, the material reaches a peak zT of 1.43 at 350 kelvin, while the fabricated module delivers a conversion efficiency of 7.5% under a 250-kelvin temperature gradient-both representing state-of-the-art performances for n-type Bi₂Te₃ systems. More broadly, this work establishes interlayer stress as a general strategy to manipulate phonons in van der Waals solids, providing previously unidentified design principles for high-efficiency thermoelectrics.