PV encapsulant formulations and stress test conditions influence dominant degradation mechanisms

Uličná, Soňa; Sinha, Archana; Miller, David C.; Habersberger, Brian M.; Schelhas, Laura T.; Owen-Bellini, Michael

doi:10.1016/j.solmat.2023.112319

Title: PV encapsulant formulations and stress test conditions influence dominant degradation mechanisms

Journal Article · 07 April 2023 · Solar Energy Materials and Solar Cells

DOI: https://doi.org/10.1016/j.solmat.2023.112319 · OSTI ID:1973218

^[1]; Sinha, Archana ^[2];

^[3]; Habersberger, Brian M. ^[4];

^[3]; Owen-Bellini, Michael ^[3]

SLAC National Accelerator Laboratory, Menlo Park, CA (United States); National Renewable Energy Laboratory (NREL), Golden, CO (United States)
SLAC National Accelerator Laboratory, Menlo Park, CA (United States)
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Dow Chemical Company, Lake Jackson, TX (United States)

Polyethylene-based poly(ethylene-co-vinyl acetate) (EVA), polyolefin elastomer (POE), and thermoplastic polyolefin (TPO) are common polymer candidates for photovoltaic (PV) module encapsulants. The choice of encapsulant must be carefully considered in novel module designs, such as bifacial glass/glass laminates, to limit performance degradation through loss of optical transmittance, mechanical integrity, and corrosion - as well as potential-induced degradation. Encapsulant quality and resilience against environmental stressors are readily influenced by the additives in the encapsulant formulation. Here, we show that, the changes in optical transmittance after UV aging result from the discoloration caused by interactions between additives, and optical scattering from changes in the polymer crystal structure. We observed competing cross-linking and chain scission mechanisms, with their kinetics influenced by the presence of oxygen and elevated temperatures. Increasing chamber temperatures from 55 °C to 85 °C during the UV stress test amplified encapsulant discoloration and promoted polymer cross-linking, causing severe, irreversible damage that remains to be proven field relevant. Damp heat aging was found to be insufficient to produce significant encapsulant degradation; however, combining stress tests sequentially allowed detection of further degradation beyond the limitations of the damp heat test alone. Appropriate degradation screening methods are necessary to uncover potential encapsulant weaknesses.

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Research Organization:: National Renewable Energy Laboratory (NREL), Golden, CO (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)

Sponsoring Organization:: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office; Durable Module Materials Consortium (DuraMAT)

Grant/Contract Number:: AC36-08GO28308; AC02-76SF00515

OSTI ID:: 1973218

Report Number(s):: NREL/JA-5900-84787; MainId:85560; UUID:c1f463fd-9ac7-47ec-b8ce-351b04b836d1; MainAdminID:69457

Journal Information:: Solar Energy Materials and Solar Cells, Vol. 255; ISSN 0927-0248

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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