by Robert Schreiber
Berlin, Germany (SPX) Dec 11, 2025
Perovskite solar cells can be made more robust, efficient, scalable and cheaper to manufacture by replacing indium tin oxide with single-walled carbon nanotubes in the device architecture, according to research led by the University of Surrey. The team reports that substituting indium tin oxide, a fragile and costly photovoltaic material, with single-walled carbon nanotubes could support flexible perovskite modules that are more affordable and mechanically resilient.
In work led by Surrey’s Advanced Technology Institute with international partners, researchers show that a straightforward sulfuric acid treatment increases the electrical conductivity of carbon nanotube films while keeping them sufficiently transparent for sunlight to reach the perovskite absorber beneath. The treatment also forms a thin nickel-based stabilising bridge layer, described as a NiSO4-NiOx interfacial layer, which improves the electrical connection between layers inside the solar cell stack.
Professor Wei Zhang, lead author from the University of Surrey’s Advanced Technology Institute, said:
“Our process resulted in a flexible perovskite solar cell free of indium tin oxide that achieved more than 20% power conversion efficiency across large areas, with small-scale devices reaching a record 24.5%. It’s safe to say that our own results took us all by surprise.”
Because carbon nanotube films can be produced using roll-to-roll chemical vapour deposition, a process already used in large-scale electronics manufacturing, the researchers state that this electrode strategy is compatible with industrial-scale production of flexible solar panels. They argue that this could deliver high-performing flexible modules manufactured at volumes suitable for commercial deployment.
Tests showed a marked improvement in operational stability. After one month of simultaneous exposure to heat, humidity and simulated sunlight, the devices retained more than 95% of their original performance, outperforming conventional indium-tin-oxide-based designs under similar conditions.
Professor Ravi Silva, co-author of the study and Director of the Advanced Technology Institute at the University of Surrey, said:
“We are now convinced that carbon nanotube electrodes can do what indium tin oxide cannot – combine high performance with mechanical strength and low cost. These results bring flexible, scalable solar technology a big step closer to real-world applications.”
The team also assessed mechanical durability by repeatedly bending the modules. Traditional indium-tin-oxide-based devices lost nearly three-quarters of their efficiency after 1,000 bends, whereas devices using single-walled carbon nanotube electrodes lost only around 5% and showed no visible cracking or delamination.
Researchers examined cost and environmental impacts as well. They estimate that producing single-walled carbon nanotube films via roll-to-roll chemical vapour deposition is around six times cheaper than indium tin oxide sputtering, lowering manufacturing costs by roughly $200 per square metre. Since indium is scarce and energy-intensive to extract, moving to carbon-based electrodes could cut both production costs and the overall carbon footprint of solar module fabrication.
The team places these results in the broader context of perovskite technology, a class of materials often highlighted in solar research for combining low-cost constituents with high light-harvesting efficiency. Perovskites can be processed at lower temperatures than silicon and formed into light, flexible devices that can bend, curve and be integrated onto a range of surfaces. However, long-term stability and fragile components have slowed commercial adoption, and the new electrode design aims directly at those constraints.
Professor Wei Zhang added: “Our work tackles one of the biggest barriers to commercialisation – cost and scalability. Flexible, lightweight solar modules like these could power everything from portable electronics to next-generation building materials.”
Research Report:Integrating SWCNT to bridge the stability divide in scalable and manufacturable flexible perovskite solar modules
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