Advanced EVA-Based Encapsulants: Final Report, January 1993--June 1997

Research output: NRELSubcontract Report


This report describes work performed by STR, Inc., under this Photovoltaic Manufacturing Technology (PVMaT) subcontract. The purpose of the three-phase PVMaT program was to further define the problem of EVA-based PV encapsulant yellowing in fielded modules, research possible chemical mechanisms, and then combat the yellowing phenomenon by developing advanced PV encapsulants. Phases I comprised aliterature search on EVA-based encapsulant browning, survey of and site visits to installations reporting discolored encapsulant in fielded modules, and analysis of browned EVA-based encapsulant. During Phase II, development work, including reformulation, resulted in four experimental encapsulants with greatly reduced browning. After 40 weeks in the Weather-O-Meter, glass/glass laminatesprepared with new formulations (standard and fast cure) showed no visible yellowing. During Phase III, these four experimental EVA-based encapsulants from Phase II were successfully prepared on a pilot scale using production equipment, and the resulting sheet was used, without significant problems, by six different module producers to fabricate full-size modules. With only a couple ofexceptions, curing of these modules was at a consistently high level, with average gel content greater than 83%, versus a typical 80% for current EVA-based materials. STR will continue to keep these modules on outdoor test after the subcontract is completed.
Original languageAmerican English
Number of pages221
StatePublished - 1998

Bibliographical note

Work performed by STR, Inc., Enfield, Connecticut

NREL Publication Number

  • NREL/SR-520-25296


  • encapsulant degradation
  • encapsulant discoloration
  • EVA-based encapsulants
  • modules
  • photovoltaic manufacturing technology (PVMAT)
  • photovoltaics (PV)


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