Researchers at the KU-KIST Graduate School of Converging Science and Technology, Korea University, have developed colloidal opaline composites for radiative cooling films, detailed in Advanced Functional Materials. Conventional nanoparticle-based thermal metamaterials were scalable but faced aggregation, haze, opacity, and limited coloration. These drawbacks restricted their effectiveness and outdoor usability. The new crystallized nanoparticle-based opaline metamaterials achieved high transparency, tunablecolors, and negligible scattering, even at increased particle loading. A polymeric topcoat further enhanced cooling and transparency while requiring fewer nanoparticles. When integrated with neutral-colored silicon photovoltaics, the films reduced operating temperature, increased open-circuit voltage, and improved power conversion efficiency. The materials also demonstrated mechanical strength and environmental durability. This research highlighted a practical thermal management approach to enhance photovoltaic efficiency and lifetime in outdoor conditions.