The performance and durability of Anti-reflection coatings for solar module cover glass – a review

Solar photovoltaics (PV) is an important source of renewable energy for a sustainable future, and the installed capacity of PV modules has recently surpassed 1TWp worldwide. PV modules experience reflection losses of ∼4% at the front glass surface. This loss can be mitigated by the use of anti-reflection coatings, which now cover over 90% of commercial modules. This review looks at the field of anti-reflection coatings for solar modules, from single layers to multilayer structures, and alternatives such as glass texturing. The materials and deposition methods used for such coatings are reviewed and a discussion around the durability of anti-reflection coatings is presented, with recent work showing that the current industry standard porous silica coatings are vulnerable to abrasion, as well as chemical thinning and humidity-related degradation. These coatings are also hydrophilic with high surface energy and greater adhesion to soiling. Multilayer coatings consisting of alternate layers of dielectric metal oxides such as ZrO2 and SiO2 are highlighted as potential alternatives to porous SiO2. The development of an abrasion standard for solar module coatings is also discussed. Suggestions for the future direction of the field are provided, including multifunctionality, such as hydrophobicity for anti-soiling, and sub-bandgap reflection for passive cooling.