Researchers from the Guangdong University of Technology in China have developed a silver paste for solar cell metallization based on biomass lignin in an effort to reduce production costs and improve the sustainability of PV cell manufacturing by replacing conventional paste components with renewable, biomass-derived materials.

“The key novelty of this work is a dual lignin engineering strategy – solvent fractionation followed by epoxidation grafting – that converts renewable lignin into a functional binder for low-temperature curable silver pastes used in silicon heterojunction (HJT) solar cells,” corresponding author Dong Yu Zhu told pv magazine. “The optimized epoxidized lignin (LEP) replaces 25% of the petroleum-based bisphenol F epoxy resin and actively participates in the curing and cross-linking network rather than acting as an inert filler. This simultaneously improves paste rheology and printability, increases the printed finger aspect ratio by 89.57%, reduces contact resistance by 62.43%, and enhances adhesion.”

The new paste was designed specifically for HJT solar cells, in which conductive silver pastes typically rely on epoxy resins to provide mechanical strength, adhesion, flexibility, and durability through cross-linking reactions during curing. However, conventional epoxy resins are petroleum-based, relatively expensive, and susceptible to aging under prolonged sunlight exposure, the scientists explained.

To address these limitations, they turned to lignin, which offers several advantages, including strong ultraviolet (UV) absorption, antioxidant properties, thermal stability, and reactive functional groups. Its incorporation into resin systems can also improve mechanical strength, toughness, and resistance to aging. “Lignin is an abundant, low-cost, renewable biopolymer obtained as a by-product of the pulping and biorefinery industries,” Zhu added.

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