Solar transparent radiators based on in-plane worm-like assemblies of metal nanoparticles

Abstract Windows with solar heating capacity can facilitate the indoors–outdoors thermal balance and improve the thermal energy efficiency of buildings, thus reducing the energy consumption in winter; however, their development has been hindered by the narrow light absorption and limited transparency of photothermal materials. In this study, transparent solar thermal surfaces on window glazing are constructed by the in-plane linear assembly of thermoplasmonics under a hierarchical electrostatic field. First results with gold nanoparticles (Au NPs) demonstrated that the hierarchical electrostatic field induced the random generation and chain growth of NP oligomers to yield controlled in-plane nanoassemblies. The linear morphology of these nanoassemblies enhanced the local electric field along the NP chains and caused additional plasmon absorption in the near-infrared spectral region, thereby improving the photothermal conversion effect without sacrificing the transparency. The solar thermal surface with Au NP assemblies increased the window glazing temperature by up to 9.8 °C under natural solar irradiation, while maintaining a high visible transmittance (>65%). The temperature increment was within the ballpark of the highest reported values and satisfied the standard requirements for thermal insulation of buildings in cold climates. This work extends new applications of linear nanoassemblies in solar energy harvesting and related energy conversion technologies.