Abstract
In the development of materials for enhanced photovoltaic (PV) performance, it is critical to have quantitative knowledge of both their initial performance and their performance over the required 25-year warranted lifetime of the PV system. Lifetime and degradation science, based on an environmental stress and response framework, is being developed to link the intensity and net stress to which materials, components, and systems are exposed to the responses observed and their subsequent degradation and damage accumulation over the lifetime. Induced absorbance to dose (IAD), a metric developed for solar radiation durability studies of solar and environmentally exposed materials, is defined as the rate of photodarkening or photobleaching of a material as a function of radiation dose. Quantitative degradation rates like IAD, determined over a wide range of stress intensities and net stresses, have the potential to predict degradation, failure, and power loss rates in photovoltaic systems over time caused by damage accumulation. Two grades of poly(methyl methacrylate) were exposed and evaluated in two cases of high-intensity ultraviolet exposures. A three- to six-fold increase in photodarkening was observed for one acrylic formulation when exposed to UVA-340 light when compared with concentrated xenon-arc exposure. The other, more highly stabilized acrylic formulation, showed up to three times more photodarkening in the same exposure.
