A highly abrasive-resistant, long-lasting anti-reflective coating for PV module glass

Abstract

More than 4% of incident light is reflected from the front cover glass of photovoltaic (PV) modules. The industry-wide trend to cost-effectively increase the efficiency of PV modules has driven the widespread adoption of anti-reflective coated (ARC) glass. The most common deposition methods for these anti-reflective (AR) coatings are wet sol-gel processes, with a small minority of glass manufacturers using vacuum-based sputtering. Most commercial sol-gel coatings consist of single layer porous silica and are highly transmissive across a broad range of the solar spectrum. The mechanical strength of these coatings is generally derived from high temperature treatment during the tempering of the glass. However, as the PV industry increasingly focuses on project levelized cost of electricity (LCOE), PV module manufactures and system owners are seeking ARC glass with increased durability and long-term performance, particularly for systems operating in medium to high soiling environments, where PV modules are subjected to airborne particle abrasion and repeated washing. In this work, we report durability test results for a new, low temperature curable sol-gel AR coating from Enki Technology, showing significantly improved abrasion-resistance compared to more traditional AR coatings. The new coating is denser than the traditional coatings and chemically derives its abrasion-resistance at relatively low process temperatures without sacrificing the optical performance. The samples under test in this work were subjected to extensive testing following the industry-standard abrasion test method in EN1096.2 and accelerated environmental test procedures in IEC61215. Our results show increased coating longevity for the new coating, up to four times greater than existing coatings with comparable optical performance. This increased mechanical strength directly translates to reduced risk of handling during manufacturing and installation, lower O&M costs, increased energy yield and reduced warranty costs.