The term “self-cleaning” may be too strong a term for this relatively new application for PVD optical thin film coatings however the coated windows apparently need less maintenance and are easier to clean.
Optical coating – titanium dioxide, TiO2
The PVD optical coating used for this application is a transparent coating titanium dioxide, TiO2 primarily because it has photocatalytic properties, which means it can decompose organic material on it’s surface when exposed to ultraviolet (UV) light. Also the TiO2 optical coating has hydrophilic properties, which means it makes it more difficult for water to nucleate and form droplets resulting in the rain water sliding over the surface taking with it the decomposed organic matter.
As UV light is abundant even in countries that don’t often see the sun between the clouds, like the UK, this optical application for PVD coatings is likely to be very profitable.