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.