Solar photovoltaic module backsheets traditionally use glass-fiber-reinforced fluoropolymers for durability and electrical insulation, but research increasingly explores bio-based materials that can reduce embodied carbon and improve end-of-life outcomes while meeting performance needs.
Cellulose and nanocellulose-based films
Researchers led by Arne Oksman Aalto University have investigated cellulose and nanocellulose as candidate backsheet layers because of their excellent mechanical strength and potential for low-permeability coatings. Cellulose derivatives and films can be combined with thin inorganic or bio-based barrier coatings to address water vapor transmission, a primary failure driver in modules. Such systems often require surface modification or multilayer architectures to approach the long-term moisture and UV resistance of synthetic backsheets.Bio-based polymers, lignin and biocomposites
Polymers derived from renewable monomers—notably polylactic acid (PLA) and bio-based polyamides such as PA11 from castor oil—are under evaluation for electrical insulation and mechanical protection. Lignin, a complex aromatic polymer abundant in pulping residues, is studied both as a UV stabilizer and as a component of composites that improve UV resistance and flame retardancy. Chitosan and protein-based films (from chitin and soy respectively) can provide barrier functionality when crosslinked or combined with nanoclays. Fraunhofer ISE and researchers including Markus Hermle Fraunhofer ISE emphasize that multilayer solutions combining a bio-based structural layer with engineered barrier coatings are the most promising near-term pathways.Relevance stems from growing regulatory and market pressure to reduce petrochemical dependence and improve recyclability. Causes for the shift include improved processing of bio-polymers, advances in nanocellulose production, and lifecycle analyses showing potential carbon advantages. Consequences include the need to revalidate long-term reliability: module degradation often arises from moisture ingress, UV-driven polymer embrittlement, and ionic contamination. Work by Sarah Kurtz National Renewable Energy Laboratory on PV reliability underscores that any bio-based backsheet must be tested under accelerated and field conditions to ensure decades-long performance.
Human and territorial nuances matter: access to sustainable feedstocks varies regionally, and reliance on agricultural inputs can raise food-versus-material tensions in some communities. Environmentally, bio-based backsheets can lower cradle-to-gate emissions and simplify organic-material recycling, but their benefits depend on production practices, coatings used, and end-of-life systems. Current evidence supports hybrid multilayer designs as the most viable route to replace fiberglass in backsheets while preserving reliability.