A Route to High Thermoelectric Performance: Solution‐Based Control of Microstructure and Composition in Ag2Se

• Published in: Advanced energy materials 2024-06, Vol.14 (22), p.n/a
• Main Authors: Kleinhanns, Tobias, Milillo, Francesco, Calcabrini, Mariano, Fiedler, Christine, Horta, Sharona, Balazs, Daniel, Strumolo, Marissa J., Hasler, Roger, Llorca, Jordi, Tkadletz, Michael, Brutchey, Richard L., Ibáñez, Maria
• Format: Article
• Language: English
• Subjects: Bismuth tellurides; Crystal defects; Crystal structure; defects; Densification; Dislocations; Figure of merit; Grain boundaries; Interstitials; Microstructure; microstructures; Room temperature; silver selenide; Sintering (powder metallurgy); Stoichiometry; strains; Synthesis; Temperature; Thermoelectric materials; thermoelectricity
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.202400408

Thermoelectric materials convert heat into electricity, with a broad range of applications near room temperature (RT). However, the library of RT high‐performance materials is limited. Traditional high‐temperature synthetic methods constrain the range of materials achievable, hindering the ability to surpass crystal structure limitations and engineer defects. Here, a solution‐based synthetic approach is introduced, enabling RT synthesis of powders and exploration of densification at lower temperatures to influence the material's microstructure. The approach is exemplified by Ag2Se, an n‐type alternative to bismuth telluride. It is demonstrated that the concentration of Ag interstitials, grain boundaries, and dislocations are directly correlated to the sintering temperature, and achieve a figure of merit of 1.1 from RT to 100 °C after optimization. Moreover, insights into and resolve Ag2Se's challenges are provided, including stoichiometry issues leading to irreproducible performances. This work highlights the potential of RT solution synthesis in expanding the repertoire of high‐performance thermoelectric materials for practical applications. A novel solution‐based synthetic approach using thiol‐amine chemistry is presented. This method enables the synthesis of thermoelectric powders at room temperature, providing unique opportunities to explore densification at unconventional lower temperatures and investigate alterations in material microstructure. The approach is exemplified through a paradigmatic case study on Ag2Se, a material benchmarked as the best n‐type alternative to bismuth telluride.