Advanced development of non‐discoloring EVA‐based PV encapsulants Available to Purchase

The purpose of this investigation was to better define the problem of field yellowing of EVA‐based PV encapsulant, through laboratory study of probable chemical mechanisms and the development of stabilization strategies for protecting EVA from discoloration. EVA from fielded modules was analyzed for vinyl acetate content, unsaturation, and additive levels. These test results were then compared to results from Xenon Arc Weather‐Ometer aged glass/EVA/glass laminates made in the laboratory. Variables evaluated in Weather‐Ometer aged laminates included ‘‘standard‐cure’’ A9918P EVA, ‘‘fast‐cure’’ 15295P EVA, low iron glass superstrate containing cerium oxide, and systematic elimination or addition of specific additives. Six significant findings were revealed: 1) Improved ‘‘standard‐cure’’ and ‘‘fast‐cure’’ type EVA encapsulants, formulations X9903P and X15303P, respectively, showed little or no yellowing after extended Weather‐Ometer exposure; 2) The use of ‘‘fast‐cure’’ EVA reduced discoloration when compared with ‘‘standard‐cure’’ A9918P EVA; 3) Glass superstrate containing cerium oxide resulted in a reduced rate of EVA discoloration; 4) ‘‘Fast‐cure’’ EVA used with glass superstrate containing cerium oxide showed no visible yellowing after 32 weeks in the Weather‐Ometer—a period estimated to be roughly equivalent to 20–30 years of exposure in the Southwest; 5) Severely discolored EVA samples from the field showed no measurable loss of acetate group and little detectable unsaturation; and 6) EVA encapsulant with a Tefzel cover exhibited no yellowing after extended Weather‐Ometer exposure.