Anti-reflection coatings for photovoltaic module glass: how long do they last in the field?

DuraMAT 1.0 Project

Fielded Module Forensics

Recipient LBNL(PI: Karin, Todd)

Abstract In order to increase photovoltaic (PV) power production, anti-reflection (AR) coatings are included on the air-glass interface on over 70% of PV modules. Typical AR coatings (e.g. porous silica) increase light transmission by ~3%, which is an easy and inexpensive way to increase the power produced by modules. However, the PV community does not currently know how long these AR coatings last in the field. This makes it difficult to quantify how coatings impact the levelized cost of electricity and whether more durable coatings are needed.

We use a commercial fiber-coupled reflectometer to measure the coating thickness and the reflection spectrum from the air-glass interface on a variety of fielded modules. The method is non-destructive, field-portable, low-power, fast, can be performed in full sunlight and does not require any electrical reconfiguration of the PV array. We measure the AR coating performance on a variety of fielded modules provided to determine the rate of coating degradation. We also use low-magnification optical color imaging in order to investigate root cause of coating degradation.