Single‐Atom and 1 nm Cluster Co‐Modified Thermoelectrics

ABSTRACT The size‐dependent electronic and phononic configurations of single atoms and nanoclusters enable tailored functionalities. Their synergistic effects also attract attention, yet precise control of anti‐aggregation states during high‐temperature operations poses formidable challenges in multiple fields such as fuel cells and thermoelectrics. Herein, we develop a solution‐processed strategy to precisely incorporate Pt species as isolated atoms (Pt 1 ) and sub‐nanoclusters (Pt n , ∼1 nm) in Bi 2 S 3 . Notably, Pt n of 1 nm size exhibit significant advantages over larger‐size counterparts in tuning electronic structure and optimizing charge transfer. Furthermore, Pt 1 and Pt n scatter 1 Å‐ to 1 nm‐ wavelength phonon that is conventionally underexplored. The 1 nm Pt n exhibits distinct force constant as compared to 3 nm Pt n , leading to ultra‐strong phonon Rayleigh scattering, which in turn significantly reduces thermal conductivity. The optimized Bi 2 S 3 ‐Pt 1 /Pt n composite achieves breakthrough thermoelectric performance, attaining a maximum zT of 1.02 at 773 K and single‐leg conversion efficiency of 1.58%, both setting benchmarks for Bi 2 S 3 systems. This strategy can also be extended to other thermoelectric material systems such as Bi 0.4 Sb 1.6 Te 3 , PbTe, or other fields including solid‐state batteries and solar cells.