Dimensionality Mismatch Enables Decoupled Heat and Charge Transport

Abstract

Decoupling heat and charge transport is a key challenge in thermoelectrics. Here, we identify a route to spatially separate phonon and carrier transport in quasi-one-dimensional materials through high-throughput screening of the Materials Project database. Representative Sn$_2$S$_3$ and SbTeI exhibit a strong-intrachain--weak-interchain bonding hierarchy that favors phonon propagation along the chains while suppressing transverse lattice heat transport. In contrast, transverse valence-band states provide effective interchain electronic coupling and relatively light hole transport. This mismatch between lattice and electronic transport dimensionalities produces an inverted thermal--electrical anisotropy. Across the screened candidates, interchain lattice thermal conductivity is strongly suppressed, whereas hole transport remains weakly anisotropic or even favors the interchain direction. For SbTeI, this decoupling yields a maximum $zT$ of approximately 2.1 near 900~K. These results establish dimensionality mismatch as a general strategy for decoupling phonon and carrier transport in thermoelectric materials.