Single‐Atom and 1 nm Cluster Co‐Modified Thermoelectrics

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 (Pt₁) and sub-nanoclusters (Pt_n, ∼1 nm) in Bi₂S₃. Notably, Pt_n of 1 nm size exhibit significant advantages over larger-size counterparts in tuning electronic structure and optimizing charge transfer. Furthermore, Pt₁ 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 Bi₂S₃-Pt₁/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 Bi₂S₃ systems. This strategy can also be extended to other thermoelectric material systems such as Bi_0.4Sb_1.6Te₃, PbTe, or other fields including solid-state batteries and solar cells.