Advanced Development of PV Encapsulants: Annual Subcontract Report, 30 December 1992 - 31 March 1994

This report describes work under Phase II of a Photovoltaic Manufacturing Technology project to conduct laboratory problem definition with an emphasis on controlled aging studies to evaluate the influence of various compositional, processing, and operating parameters on ethylene vinyl acetate (EVA) discoloration. In support of future accelerated UV aging studies (AAS) of coupon-sized EVAlaminates, an Atlas xenon arc Ci35A Weather-Ometer was procured, installed, and calibrated for temperature and irradiance. In preparing for the AAS studies, UV-visible spectroscopy measurements were performed on various types of low-iron glass, representive of materials used for module superstrates. It was discovered that the transmission spectra of some of the grades in the UV region from 250to 400 nm was significantly different. Older grades of Solatex and solite, and StarPhire 'cut off' well below 290 nm, while newer grades of Solatex and Solite, and StarPhire and Airphire greatly reduce the UV transmittance between 280 and 330 nm. Controlled aging studies are presently underway at 0.55 W/m2, 340 nm, and 100 degrees C, and we expect comparative data on yellowing to be availablesoon.