High Efficiency Anti-Reflective Coating for PV Module Glass

Without antireflective coating, more than 4% of incident light is reflected from the standard front cover glass of photovoltaic (PV) modules. Module efficiency is one of the largest levers to impact the cost-per-watt of solar and recovering some of this reflected light with a simple anti-reflective coating (ARC) has become widespread. The types of ARC can vary in deposition method (roll coating, spray coating, sputtering, etc.) as well as composition and performance. The most widely adopted coatings today are based on a porous silica film with a thickness optimized for the solar spectrum. Current coatings, however, have room for improvement in both the performance and cost which means that manufacturers are actively looking for new solutions that drive down the levelized cost of electricity (LCOE). In this work, we report the test results for a new AR coating from WattGlass showing significantly improved optical performance compared to the traditional AR coatings. The new coating takes advantage of water-based chemistry that is more environmentally friendly than the sol-gel processes used in standard production coatings. This chemistry allows a high performance and durable coating to be deposited and cured at room temperature and is compatible with industry standard glass tempering conditions. The samples under test in this work were subjected to extensive optical performance testing at material and mini-module level. Our results show increased optical performance for the new coating, with solar weighted transmittance improvements as high as 3.1%. This increased optical performance directly translates to increased energy yield, lower LCOE and reduced warranty costs.

I. Introduction

Due to the mismatch in index of refraction between air and glass, 4% of normally incident light is lost due to reflection at the interface of air and PV module glass. As the PV industry is driving towards higher efficiencies at even lower costs it has widely adopted the anti-reflective coating (ARC) for PV module front cover glass. It has been estimated that greater than 92% of silicon PV modules are now made with ARC glass [1].