Promising Materials for Thermoelectric Applications
โ
Every year, we waste approximately two-thirds of the energy as heat. This lost heat contributes to both the climate and resource crises.
Recovering and reusing waste heat will reduce our reliance on primary energy sources. Thermoelectric materials can convert waste heat to electricity and vice versa. The performance of these materials is evaluated by a dimensionless figure of merit (zT), given by
where ๐, ๐, ๐, ๐๐ and ๐๐ represent Seebeck coefficient, electrical conductivity, temperature, electrical thermal conductivity, and lattice thermal conductivity, respectively. These parameters are unfavourably interdependent, limiting zT from reaching its maximum potential.
One approach to optimise its performance is to identify materials with intrinsically low lattice thermal conductivity.[1] Alkali Metal Chalcogenides (ABZ, A=Alkali metal, B=Transition metal, Z=Chalcogen), exhibit intrinsically low ๐๐ due to localised vibrations, anharmonicity, and heavy metal ions in the crystal structure.[2] These features make them promising materials for thermoelectric applications.
In that direction, our group reported colloidal hot-injection synthesis of ternary caesium copper selenide (Cs-Cu-Se) nanocrystals (NCs), achieving precise control over phase, size, and morphology through tailored precursor-ligand modulation. (3) This strategy enabled the systematic exploration of stable and metastable CsโCuโSe phases and the mechanistic investigation of nucleation and growth, providing insight into phase modulation and nanoscale dimensional control. CsCuSe NCs exhibit low lattice thermal conductivity (โผ0.5 Wmโ1Kโ1) and an experimental zT of 0.27 at 718 K.
(1) Snyder, G. J.; Toberer, E. S. Complex Thermoelectric Materials. Nat. Mater. 2008,7 (2), 105โ114.
(2) McKeever, H.; Patil, N. N.; Palabathuni, M.; Singh, S. Functional Alkali Metal-Based Ternary Chalcogenides: Design, Properties, and Opportunities. Chem. Mater.2023, 35 (23), 9833โ9846.
(3) Patil, N. N.; Wu, R.; Fiedler, C.; Kapuria, N.; Nan, B.; Jakhar, N.; Cabot, A.; Ibรกรฑez,M.; Ryan, K. M.; Ganose, A. M.; Singh, S. Layered Alkali-Copper Selenides: Deciphering Thermoelectric Properties and Reaction Pathways for Nanostructuring ฮฒ-CsCu5 Se3. ACS Energy Lett. 2026, 11 (1), 481โ488.