Carrier Concentration Optimization Facilitates High Thermoelectric Performance in Solution-Grown Y and Pb Codoped SnSe Nanorods

Here, Pb/Y codoped SnSe nanorods were fabricated via a bottom-up, cost-effective hydrothermal method. The formation of nanorod structures generating high-density grain boundaries significantly enhances phonon scattering, serving as the primary mechanism for lattice thermal conductivity reduction. Furthermore, Y-element enrichment regions, nanoprecipitates, and dense dislocation networks provide additional phonon scattering that further suppresses phonon transport. These multiscale structural features synergistically impede phonon propagation across all frequency ranges, ultimately yielding an ultralow κ_L of 0.157 W m^-1 K^-1 at 873 K in the Pb and Y codoped SnSe nanorods. Meanwhile, Pb/Y codoping enhances carrier concentration, leading to a sharp increase in electrical conductivity in Sn_0.99-xPb_0.01Y_xSe nanorods. Concurrently, the electrical transport properties are significantly improved, resulting in enhanced power factor. As a result, this carrier and phonon synergistic optimization contributes to a peak ZT of 1.74 at 873 K in Sn_0.985Pb_0.01Y_0.005Se nanorods. This work provides insights for developing high-performance polycrystalline SnSe through advanced doping strategies and structural design.