A new, greener, lower-toxicity method could help manufacture flexible perovskite solar panels at an industrial scale using a roll-to-roll printing.The University of Surrey has proposed this safer method for producing high-efficiency perovskite solar modules. It uses a low-toxicity, bio-derived solvent formulation that operates at room temperature and reduces the use of hazardous industrial chemicals. The process uses continuous printing techniques similar to newspaper printing, which could make large-scale production both eco-friendly and cost-effective. “The potential impact of our innovation extends beyond simply replacing a hazardous solvent. A process based on easy-to-use, non-toxic solvents and simpler coating steps reduces the need for solvent handling, waste treatment and the safety infrastructure that goes with them,” said Professor Ravi Silva, Distinguished Professor, Director – Advanced Technology Institute (ATI) and Head of NanoElectronics Center. Roll-to-roll printing. Credit: Surrey University. Ditch toxic chemicalsLightweight, flexible perovskite solar cells have long promised to replace silicon panels. But hazardous production processes have hindered their commercial potential. Typically, creating printable perovskite inks requires large quantities of toxic solvents, including dimethylformamide and acetonitrile. These chemicals endanger factory workers and create severe environmental burdens. Surprisingly, just a single gigawatt-scale manufacturing line can consume over 90,000 liters of toxic solvent.Now, that chemical barrier is crumbling. The researchers discarded the hazardous legacy chemicals. And formulated a “Significantly Reduced-Toxicity” (SRT) ink system built on bio-derived ingredients. The team created a quick-drying formulation using a combination of ethanol and 2-methyltetrahydrofuran, a eco-friendly solvent derived from agricultural and forestry waste. This bio-derived mixture eliminates the need for anti-solvent processing steps. Skipping those harsh steps saves energy and conserves raw materials during manufacturing.Flexible mini-modulesGoing green did not mean sacrificing performance.Using a roll-to-roll compatible bar-coating method, the team printed solar mini-modules with an active area of 11.5 square centimeters. Coated at room temperature and dried with a quick gas jet, these flexible panels reached power conversion efficiencies over 18.2 percent while maintaining rock-solid stability under continuous illumination.The mini-modules feature an inverted architecture with bar-coated, self-assembled monolayers as hole-transport layers. This structure cuts the need for additional interlayers. According to the study, the team used a laser-based P1-to-P4 scribing process to monolithically link individual solar cells for industrial module patterning. The scientific paper further added that the development tested the eco-friendly solvent using a gas-blown bar-coating method. But the team also made sure it works with standard slot-die coating machines used in factories.As a result, the process could be integrated into high-throughput factory floors in the future. It would ensure that the eco-friendly manufacturing technique is ready for large-scale industrial deployment.“We want to help make clean energy available across the world, and if we can support decarbonization at scale in the same step, that is a double win for society,” Silva added. Integrating green chemistry into high-speed printing techniques makes the large-scale production of flexible solar cells a practical near-term reality. Flexible perovskites could soon power everything from portable consumer electronics and building-integrated windows to ultra-lightweight solar arrays launched into space. The study findings were published in the journal Nano Energy.