Emerging Markets for Polyolefins in the Solar Industry

Polyolefins are increasingly replacing conventional materials as encapsulant films in photovoltaic solar panels.

Polyolefins have gained significant market share as encapsulants for photovoltaic modules. Since the 1980s, chemically crosslinked EVA has been the most common material for this purpose. EVA provides good durability and performance but requires chemical crosslinking for thermos-mechanical stability. Thus, it has a limited shelf life, an intensive lamination process, and can form acetic acid during degradation, leading to corrosion. The world market share for EVA-based encapsulants has been steadily dropping in favor of polyolefin and EVA/polyolefin elastomer (POE) mixtures.

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How Polyolefins Gained a Stronghold in Encapsulants

In the mid-1990s, researchers began investigating polyolefins as alternatives to EVA encapsulants. This research showed that polyolefins may avoid adhesion failure while providing better ultraviolet (UV) stability. Thus, these materials presented a suitable alternative to EVA if not used at high operating temperatures. In the following years, research continued to expand the use of polyolefins for encapsulation.

In 2008, for example, The Dow Chemical Company developed functionalized polyolefins for encapsulation. These materials reduced moisture permeation, did not require curing, and did not produce acetic acid. They had a lower density than EVA and better adhesion to glass.

More recent research has developed innovative polyolefin encapsulants, cross-linked POEs, and thermoplastic polyolefin encapsulants. These materials reduce corrosion, potential-induced degradation, ion diffusion, and discoloration. Additionally, recent research has focused on compatibility with novel technology and modules for specific applications and environmental conditions.

Preventing Delamination

Delamination occurs when the encapsulant detaches from glass or backsheet of a solar panel. Environmental stresses and external mechanism loads, such as those caused by wind and snow, can lead to delamination. Acetic acid formation from EVA encapsulants can lead to delamination, but polyolefin encapsulants demonstrate improved robustness in comparison. Research has shown that polyolefin encapsulants show strong initial adhesion compared to EVA. Nevertheless, few long-term studies have investigated behavior over time, leaving a risk of unexpected behavior.

Long-Term Outlook

The photovoltaic industry’s shift to bifacial cells and double-glass structures has driven the growth of polyolefin encapsulant use. Bifacial cells capture light from both sides of the solar panels. Polyolefin encapsulants enhance the durability and optical properties of these double-sided cells.

Polyolefin encapsulants show promise for reliability, but only time and research will uncover unknown failure modes. These may arise from inappropriate formulations or insufficient processing. Future research may seek to investigate field reliability to aid manufacturers with appropriate polyolefin material selection for solar panels.