Accelerated UV test methods and selection criteria for encapsulants of photovoltaic modules

Photovoltaic modules are exposed to extremely harsh conditions of heat, humidity, high voltage, mechanical stress, thermal cycling and ultraviolet (UV) radiation. The current qualification tests (e.g. IEC 61215) do not require UV exposure high enough to evaluate a 20⁺ year lifespan. Methods to quickly test the UV durability of photovoltaic materials are needed. In considering encapsulant materials, the initial performance and material cost are important but the ability to maintain adhesion and transmissivity under UV exposure are equally important. This can be evaluated under highly accelerated conditions with light from a xenon arc lamp using glass that transmits more UV radiation than standard cerium doped glass. The use of highly transmissive glass results in an effective UV dose that is about 3.8 times higher with regard to adhesion. With this configuration a UV dose equivalent to 20 years of exposure can be obtained in just over 6 months using standard commercial accelerated stress chambers.