Pressure-induced remarkable four-phonon interaction and enhanced thermoelectric conversion efficiency in CuInTe2

Hydrostatic pressure (P) has been regarded as an effective approach to improve the performance of thermo-electric materials. Although a positive correlation between its thermoelectric performance and pressure has been demonstrated experimentally for CuInTe2, the underlying physical mechanism remains unclear. Herewith, we investigate the inherent mechanism of hydrostatic pressure-induced electron-thermal transport properties and thermoelectric conversion efficiency for CuInTe2. It is demonstrated that the pressure limits the thermal transport behavior of heat-carrying phonons by changing phonon dispersion, where the broadening of the low-lying phonon bandwidth caused by the compression promotes the dominance of the four-phonon (4ph) scattering mechanism, especially at high temperatures. In addition, the power factor has achieved a huge net increase through the convergence of the valence band edge despite the presence of strong coupling between electron transport parameters. Such bidirectional optimization gives rise to a remarkable enhancement of thermoelectric conversion efficiency. Our work highlights the significant effect of pressure-induced 4ph interaction in CuInTe2, which brings deeper insights into the behavior of thermoelectric materials under extreme pressure environments.