The multi-dimensional approach to synergistically improve the performance of inorganic thermoelectric materials: A critical review

This review discusses the recent progress and persistent challenges toward achieving high thermoelectric (TE) figure of merit with inorganic TE materials. For decades, the interdependence between the relevant thermoelectric parameters has been the main impediment halting the large-scale usage of these materials for clean energy production. The thermoelectric performance can be improved by reducing the thermal conductivity or maximizing the power factor. We summarized the state-of-the-art methodologies adopted to reduce the lattice thermal conductivity to its amorphous limit, thus enhancing the figure of merit. The synergistic approach of utilizing valence band convergence, carrier filtering together with resonant levels formation has also been found to improve the power factor and the figure of merit of some TE materials. The work gives particular emphasis to systems in which spectacular advances have been demonstrated, such as chalcogenides, Heusler compounds, clathrates, and skutterudites. We further summarized different materials fabrication techniques with their success in tuning the TE performance. A discussion on future perspective where both the power factor and the thermal conductivity can be significantly tuned via a multi-scale approach to yield high-performance TE materials for industrial applications has been presented.