New horizons in thermoelectric materials: Correlated electrons, organic transport, machine learning, and more

Thermoelectrics represent a unique opportunity in energy to directly convert thermal energy or secondary waste heat into a primary resource. The development of thermoelectric materials has improved over the decades in leaps, rather than by increments—each leap forward has recapitulated the science of its time: from the crystal growth of semiconductors, to controlled doping, to nanostructuring, and to 2D confinement. Each of those leaps forward was, arguably, more a result of materials science than physics. Thermoelectrics is now ripe for another leap forward, and many probable advances rely on new physics outside of the standard band transport model of thermoelectrics. This perspective will cover a limited selection of how thermoelectrics can benefit from new discoveries in physics: wave effects in phonon transport, correlated electron physics, and unconventional transport in organic materials. We also highlight recent developments in thermoelectrics discovery aided by machine learning that may be needed to realize some of these new concepts practically. Looking ahead, developing new thermoelectric physics will also have a concomitant domino effect on adjacent fields, furthering the understanding of nonequilibrium thermal and electronic transport in novel materials.