PV Encapsulant Formulations and Stress Test Conditions Influence Dominant Degradation Mechanisms

Sona Ulicna, Archana Sinha, David Miller, Brian Habersberger, Laura Schelhas, Michael Owen-Bellini

Research output: Contribution to journalArticlepeer-review

7 Scopus Citations

Abstract

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.

Original languageAmerican English
Article number112319
Number of pages11
JournalSolar Energy Materials and Solar Cells
Volume255
DOIs
StatePublished - 15 Jun 2023

Bibliographical note

Publisher Copyright:
© 2023 Elsevier B.V.

NREL Publication Number

  • NREL/JA-5900-84787

Keywords

  • Accelerated stress testing
  • DuraMAT
  • Encapsulants
  • Glass/glass
  • PV reliability

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