Photothermal Conversion of Solar Energy: Mechanisms, Designs, and Energy Applications

ABSTRACT Meeting the growing global demand for energy while mitigating environmental impacts requires efficient solar‐energy technologies. Photothermal conversion enhances solar‐to‐thermal performance through multiscale control of light absorption, energy conversion, and thermal management. Despite substantial progress, previous reviews have often focused on individual materials or applications rather than shared physical principles and the links among mechanisms, material and structural design, and diverse energy applications. This review summarizes recent advances in solar photothermal conversion for energy applications. It describes the principal light‐to‐heat conversion mechanisms, including plasmonic localized heating, non‐radiative relaxation, and molecular vibrations. By integrating the intrinsic optical properties of materials with nanostructure engineering, hierarchical porous networks, multilayer films, and biomimetic structures, spectral responses, heat transfer, and mass transport can be controlled across micro‐ and nanoscales. This framework guides the design of systems for interfacial solar evaporation, photothermal catalysis, building energy conservation, and thermoelectric power generation. Key challenges to large‐scale deployment, including environmental adaptability, long‐term stability, and cost‐effectiveness, are also analyzed. Finally, emerging directions such as coupled dynamic spectral modulation and AI‐driven inverse design are highlighted as routes toward practical photothermal technologies. This review provides insights into the development of multifunctional materials and intelligent systems for the broader deployment of solar photothermal technologies.