Boosting power factor via self-exsolved metallic nanonetworks in SrTiO₃-based thermoelectric thin films

Perovskite oxide SrTiO₃ is promising for thermoelectrics due to its high intrinsic Seebeck coefficient and stability, but its overall power factor still needs further improvement. Compositing with metallic phases can enhance conductivity, yet precise nanoscale control remains a challenge. Here, we employ exsolution to self-assemble metallic nanonetworks within La-doped SrTiO₃ (La:SrTiO₃) epitaxial thin films on LSAT (001) substrates. By controlling exsolution conditions to tune nanoparticle size and density, we achieve a dense, uniformly distributed nanonetwork with strong interfacial bonding, significantly enhancing electrical conductivity. This yields a superior power factor, with a peak PF_max of ∼1352 μW m⁻¹ K⁻² at 528 K and a high average PF_ave of ∼1106 μW m⁻¹ K⁻² from room temperature to 886 K. These values are highly competitive within state-of-the-art n-type oxide thermoelectrics. This work establishes exsolution as a powerful pathway for nano-composite engineering in perovskite oxides, offering guidance for the design of high-performance thermoelectric single-crystal thin films.