Paper solar cells: the future for PV?

Reseachers from the South China University of Technology, alongside their counterparts from the University of Nebraska-Lincoln, have published an intriguing report on a new type of paper they claim can be used as material for next-gen solar cells and boasts a transparency of 96%.

The team’s report, published recently in Nano Letters, outlines how their new wood-based paper product outperforms all other materials in both optical transparency and optical haze, delivering low-cost, high-efficiency and environmentally friendly performance that could revolutionize the solar cell industry.

According to the report, the paper is made of TEMPO-oxidized wood fibers that eliminate micropores and instead produce nanopores, which allow for ultrahigh transparency values of 96%, and optical haze values of 60% – the highest optical haze value reported among transparent substrates. Typically, materials that boast a high optical transparency (allowing for good light transmission) of over 90% generally have low optical haze values (the scattering and, therefore, the absorption of transmitted light within the material) of less than 20%.

The TEMPO treatment weakens the hydrogen bond between the microfibers that make up typical wood fibers, causing them to swell and collapse into a tightly packed structure that eliminates micropores. Ordinarily, the wood fibers in normal paper have a low optical transparency because the microcavities that exist within the porous structure cause light scaterring. But with the micropores removed and replaced by nanopores, optical transparency is improved.

For solar cell testing, treated wood fiber paper was coated on to silicon slabs, with lab experiments showing that light harvesting improved by 10%. Hence, pre-existing and installed solar cells could also benefit from the technology thanks to a simple lamination process.

"The papers are made of ribbon-like materials that can stack well without microsize cavities for high transmittance, but with nanopores for high optical haze," Liangbing Hu, assistant professor in the Department of Materials Science and Engineering at the University of Maryland, and co-author of the report, told

Hu has expressed an interest in working closely with solar cell makers with a view to further testing, evaluating and perhaps commercializing the product, which is currently still at an early testing stage. Mooted low-cost, eco-friendly adaptations of traditional technology are regularly met with a fair amount of guarded skepticism, but the promised efficiencies this paper could bring to the solar PV industry certainly warrant further investigation.