In a discovery inspired by nature, a team of researchers have found that water-gel-based solar devices, or artificial leaves, can act like solar cells to produce electricity. According to the team from North Carolina State University, these solar cells also have the potential to be less expensive and more environmentally friendly than the current standard-bearer: silicon-based solar cells. The bendable devices are composed of water-based gel infused with light-sensitive molecules – the researchers used plant chlorophyll in one of the experiments – coupled with electrodes coated by carbon materials, such as carbon nanotubes or graphite. The light-sensitive molecules get "excited" by the sun's rays to produce electricity, similar to plant molecules that get excited to synthesize sugars in order to grow, according to NC State's Dr. Orlin Velev, Invista Professor of Chemical and Biomolecular Engineering and the lead author of a paper published online in the Journal of Materials Chemistry. Velev said that the research team hopes to "learn how to mimic the materials by which nature harnesses solar energy." Although synthetic light-sensitive molecules can be used, he said naturally derived products – like chlorophyll – are also easily integrated in these devices because of their water-gel matrix. Now that they've proven the concept, Velev said the researchers will work to fine-tune the water-based photovoltaic devices, making them even more like real leaves. "The next step is to mimic the self-regenerating mechanisms found in plants," he said. "The other challenge is to change the water-based gel and light-sensitive molecules to improve the efficiency of the solar cells." Velev even imagines a future where roofs could be covered with soft sheets of similar electricity-generating artificial-leaf solar cells. "We do not want to overpromise at this stage, as the devices are still of relatively low efficiency and there is a long way to go before this can become a practical technology," he said. "However, we believe that the concept of biologically inspired 'soft' devices for generating electricity may in the future provide an alternative for the present-day solid-state technologies." Researchers from the Air Force Research Laboratory and Chung-Ang University in Korea co-authored the study. The study was funded by the Air Force Research Laboratory and the US Department of Energy. The work is part of NC State's university-wide nanotechnology program, Nano@NC State. For more information, visit: www.ncsu.edu