EVA degradation mechanisms simulating those in PV modules

Conference · Tue Dec 01 00:00:00 EST 1992 · AIP Conference Proceedings (American Institute of Physics); (United States)

OSTI ID:5390781

Pern, F J; Czanderna, A W ^[1]

---

1. Measurements and Characterization Branch, National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

Yellow-browning of the ethylene-vinyl acetate (EVA) copolymer encapsulant used in PV modules has resulted in significant power losses of over 50% of the initial power output. The weathering-degraded yellow-brown EVA films have lost the ultraviolet (UV) absorber, Cyasorb UV 531[sup (R)], and the degree of cross-linking (gel content) has increased. EVA degradation mechanisms identified thus far are discussed in this work. Upon exposure to UV light at 45[degree]--85 [degree]C, virgin EVA films that are stabilized with Cyasorb UV 531[sup (R)] and two antioxidants show an increase in the gel content, a gradual loss of Cyasorb by photooxidation, and the generation of acetic acid. The deacetylation reaction, which leads to the formation of polyenes, also occurs significantly in the films heated in the dark at 130 [degree]C for five days. Acetic acid thermally catalyzes the EVA film discoloration at 85[degree]--130 [degree]C, which increases from a light yellow to a yellow-brown color as the heating temperature increases. The factors can account for the yellow-browning of the EVA in the accelerated testing of mini-modules, and the discoloration is more profound when exposed to UV light at 85 [degree]C than when heated in the dark at the same temperature. In the presence of the EVA-produced acetic acid, oxygen, and sunlight exposure, the Cu buslines that were coated with a thin layer of Pb-Sn alloy showed significant oxidation and metal interdiffusion, which in turn may contribute to the resistance increase and hence the current loss reported for weathered PV modules.

• DOE Contract Number: AC02-83CH10093
• OSTI ID: 5390781
• Report Number(s): CONF-9205115-; CODEN: APCPCS
• Journal Information: AIP Conference Proceedings (American Institute of Physics); (United States), Vol. 268:1; Conference: 11. review meeting of the National Renewable Energy Laboratories: photovoltaic advanced research and development, Lakewood, CO (United States), 13-15 May 1992; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
PHOTOVOLTAIC CELLS
THERMAL DEGRADATION
ACETIC ACID
BLEACHING
CATALYTIC EFFECTS
COPOLYMERS
OXIDATION
PERFORMANCE TESTING
SIMULATION
ULTRAVIOLET RADIATION
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DIRECT ENERGY CONVERTERS
ELECTROMAGNETIC RADIATION
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PHOTOELECTRIC CELLS
POLYMERS
RADIATIONS
TESTING
140501* - Solar Energy Conversion- Photovoltaic Conversion