Solar water evaporation by black photothermal sheets

Solar energy-to-heat conversion for steam generation is an essential metrology for power generation, water purification and desalination. Harvesting light energy and converting it to heat as terminal energy by black photothermal sheets is a novel strategy to attain this goal. This technology rely on use of black nanomaterials as light absorber to increase the absorption and conversion efficiency of solar energy. Fundamental understanding of their structure-property has to be fully exploited for further developing efficient solar-to-heat systems. This report summarizes physical understanding and experimental advances in development of black photothermal sheets for solar water evaporation. We examine the popular photothermal systems with remarkable vapor generation performance to identify the state-of-the-art of the device design. Three groups of the photothermal sheet are discussed in terms of different light-harvesting materials, such as carbon-based sheets, plasmonic sheets as well as semiconducting sheets. The physical difference of these novel devices with their steam releasing property are also highlighted.