Multifunctional polymer-based coatings for outdoor glass surfaces: A state of the art

The development of innovative coatings with advanced multifunctional properties can lead the way to a more sustainable future. During the last decade, the global use of solar energy has been accelerating while there is a growing need for more energy-efficient buildings. Recent research efforts have focused on developing smart coatings that can rectify and amplify the role of protective glass surfaces which are mainly used in photovoltaic panels and in building windows. These surfaces suffer from the deposition of dirt, which compromises the power output of photovoltaic panels and stains the building facades. The application of novel self-cleaning, antifouling coatings on these surfaces can offer a proactive solution. Many research groups have suggested the use of antireflective coatings that can improve the transparency of glass, as well. Furthermore, the concept of radiative cooling coatings has been gaining attention as a method to lower the operating temperature of solar panels and to improve the temperature management of indoor spaces. In recent years, many hybrid polymer-based coatings have been proposed for these purposes, and the goal of this review is to summarize them and to assess their performance. The first part of this article is concerned with the selection of materials and the manufacturing processes. The second part is focused on the properties of these coatings, namely their optical transparency, their self-cleaning ability, their antireflective and radiative cooling performance, as well as their mechanical and chemical durability. The connection between the selection of materials, the coating formulation and the desired properties will be highlighted. Finally, future directions in this research field will be proposed.