Phonon and electron transport engineering for enhanced thermoelectric performance and the challenges of device integration

Thermoelectricity has long been recognized as a transformative technology for power generation and cooling, owing to its capability to convert heat directly into electricity and vice versa, thereby facilitating cost-effective and environmentally friendly energy conversion. Following a period of modest activity, the field has experienced a remarkable resurgence since 2000, driven by significant advancements in the development of a diverse array of new materials and compounds, alongside enhanced capabilities for controlled nanostructuring. This rapid growth and the innovative breakthroughs observed over the past two decades can be largely attributed to a deeper understanding of the physical properties at the nanoscale. Among the various thermoelectric materials, nanostructured variants exhibit the highest potential for commercial application due to their unprecedented thermoelectric performance, which arises from substantial reductions in thermal conductivity. However, further advancements will not rely solely on nanostructuring; they will also necessitate novel electronic structure design concepts that require a comprehensive understanding of the complexities of electronic and phonon transport. These developments present significant opportunities for thermoelectric energy harvesting, power generation, and cooling applications. This article aims to summarize and elucidate the breakthroughs reported in recent years, discuss future avenues that integrate nanostructuring concepts with the rich electronic structures of novel materials, and provide a critical overview of the future directions in thermoelectric materials research. Additionally, it offers a comprehensive overview of state-of-the-art thermoelectric materials and devices and a summary of the challenges associated with transitioning these materials into practical devices.