Current and future coating technologies for architectural glazing applications

• A review of the state-of-the-art coating technologies for glazing applications is reported. • Static coating technologies with fixed optical properties are compared to dynamic coatings. • Electrothermal coatings and photothermal coatings are compared. • Recent evolution in electrochromic and gasochromic coatings is reported. • An ideal passive dynamic hybrid photo-thermochromic coating on flexible films is presented. This paper presents a comprehensive review of the current state-of-the-art coating technologies for glazing applications. The main objective is to collect and present current commercially available technologies on today's market and future research prototypes to identify the most promising coating technologies. Several static coating technologies with fixed optical properties are compared, including low emissivity, electrothermal and photothermal coatings. Low-E coatings are the current industry standard and have almost reached their full energy-saving potential. Hence, electrothermal coatings that convert electricity to heat by the Joule effect are discussed, together with their limitations of needed power supply. To overcome these issues, photothermal coatings have been proposed to improve the glazing thermal performance by absorption of ultra-violet and near-infrared radiation. On the other hand, dynamic coatings can modulate solar gains by switching between clear and tinted states in response to external stimuli. Electrochromic and gasochromic coatings are still limited by high costs. In comparison, photochromic and thermochromic coatings are more accessible and less complex passive technologies, although photochromic coatings are still hindered by low bleaching rates and poor cyclic stabilities. In comparison, thermochromic coatings are more mature, especially those based on vanadium dioxide. This review shows that both static and dynamic technologies thrive to enhance optical and thermal performances while providing an opportunity for the realization of durable next-generation dynamic windows. In particular, the development of passive dynamic hybrid photo-thermochromic coatings seems the most promising trajectory.