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.
The researchers investigated two approaches to incorporating lignin into low-temperature curable silver pastes. The first involved directly blending fractionated alkali lignin with bisphenol F epoxy resin as a partial resin replacement. The second involved using chemically modified, epoxidized lignin to participate in the resin’s curing network. Both approaches were intended to improve paste viscosity, printability, adhesion, electrical conductivity, and ultimately solar cell efficiency.
Two types of lignin, alkali lignin (AL) and enzymatic hydrolysis lignin (EHL), were selected, with AL further fractionated using ethanol and ethyl acetate. LEP was then synthesized by chemically modifying the ethyl acetate-soluble fraction with a silane coupling agent. The silver paste contained three types of silver powder, along with resins, curing agents, dispersants, and solvents. The total silver content was maintained at 92–93 wt%, with a silver-to-resin ratio of 30:1.
Different lignin concentrations and resin substitutions were investigated to assess their effects on paste performance. The mixtures were homogenized and processed using a three-roll mill before being screen-printed onto monocrystalline silicon wafers measuring 158.75 mm × 158.75 mm. The printed samples were subsequently cured at 180 C for 30 minutes.
Various characterization techniques, including Fourier-transform infrared spectroscopy (FTIR), rheometry, microscopy, and electrical resistance measurements, were used to evaluate the chemical, mechanical, morphological, and electrical properties of the pastes. The power conversion efficiency of the resulting HJT solar cells was then measured through current–voltage testing.
The analysis revealed denser silver particle packing, reduced internal porosity, and improved contact between the silver electrodes and silicon substrates. These structural improvements were also found to promote the formation of continuous conductive pathways and reduce electrical losses.
The scientists also found that the LEP formulation increased the power conversion efficiency of the HJT cells from 25.01% to 25.96%. “This represents an absolute gain of 0.95 percentage points over the control, offering a sustainable bio-based route for high-efficiency HJT metallization,” Zhu stated.
“These findings indicate that incorporating an appropriate amount of LEP promotes curing and cross-linking reactions, resulting in a stable three-dimensional network that improves paste rheology, printed grid morphology, interfacial contact, and electrical conductivity,” he concluded. “These enhancements in the cured silver grid ultimately contribute to improved photovoltaic performance in HJT solar cells.”
The research is presented in the study “Engineered lignin unlocks low-temperature curable silver pastes for high-efficiency silicon heterojunction solar cells,” published in Solar Energy Materials and Solar Cells.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: [email protected].
Comments
Please login to comment
Friday, October 23, 2026
11:00 am – 12:00 pm CEST, Berlin, Paris, Madrid
Monday, October 12, 2026
10:00 am – 11:00 am CEST, Berlin, Paris, Madrid
Thursday, October 8, 2026
11:30 am – 12:30 am CEST, Berlin, Paris, Madrid
The new issue of pv magazine Global is out now!
Available in print and digital – get your copy today!
Monday, October 26, 2026
10:30 am – 11:30 am CEST, Berlin, Paris, Madrid
Thursday, October 7, 2026
11:00 am – 12:30 pm CEST, Berlin, Paris, Madrid
pv magazine USA hosts its multi-day virtual event on U.S. solar and energy storage, covering domestic manufacturing, distributed energy and the growing role of solar-plus-storage in meeting AI-driven power demand.
You have no items in your basket.
