Structure‐Interface Synergistic Cu–Zn Hybrid Films for High‐Efficiency Thermal Management and Photothermal Conversion

ABSTRACT Advancing photothermal materials requires synergy between light collection and efficient heat transport. However, nanoscale photothermal fillers, while strengthening absorption, are constrained by limited dispersibility and high interfacial resistance. By contrast, micrometer‐scale metal fillers aid conduction yet lie outside the plasmonic regime, and their smooth surfaces promote specular reflection, which limits light capture. Consequently, leveraging their latent complementarity is crucial. Here, a multiscale structure and interface strategy is introduced, in which electrodeposition and alloying build a structured Cu–Zn interface with bead‐chain‐like nanostructures along the flake edges, thereby forming a metallic backbone that lowers interfacial thermal resistance and simultaneously promotes light capture and heat transfer. Specifically, at 8 vol% loading the composite attains through plane and in plane thermal conductivities of 1.06 and 2.73 W m ⁻¹ K ⁻¹ . Moreover, it shows broadband absorption (200–800 nm) and exhibits rapid heating and steady state output under both broadband solar and UV irradiation, under 365 nm illumination the film warms to 91.3°C within 30 s, indicating a favorable steady state photothermal heating efficiency under the defined conditions. This strategy offers a scalable route for interface engineering of microscale metal fillers and thus couples’ light absorption, heat transport, and energy use in solar‐responsive and renewable energy conversion systems.