Improved photostability of NREL-developed EVA pottant formulations for PV module encapsulation

Several new formulations of solar cell module ethylene vinyl acetate (EVA)-based encapsulant have been developed at NREL and have greatly improved photostability against UV-induced discoloration. The new EVA formulations use stabilizers and a curing agent entirely different from any of those used in existing formulations. No discoloration was observed for the laminated and cured samples that were exposed to a ~5-Sun UV light (300-400 nm) from a solar simulator at a black panel temperature (BPT) of 44°±2°C for ~3250 h followed by at 85°C for ~850 h, an equivalent of approximately ~9.4 years for an daily, 1-Sun solar exposure in Golden, Colorado. Under the same conditions, substantial discoloration and premature delamination were observed for two commercial EVA formulations. Encapsulation with the new EVA formulations should extend the long-term stability for PV modules in the field, especially when coupled with UV-filtering, Ce-containing glass superstrates