Scientists have developed a new, water-based, solar device that acts as a type of artificial leaf. The device uses a water-based gel infused with light-sensitive molecules, along with electrodes that are coated with carbon materials, such as carbon nanotubes or graphite. When these molecules are stimulated by the sun they produce electricity, in a similar way to plant molecules synthesising sugars when they are excited.

These new, bendable, bio-mimetic solar cells can use both synthetic light-sensitive molecules and also naturally derived products such as chlorophyll, which can be integrated because of their water-gel matrix. The research, which was published in the Journal of Materials Chemistry [Koo et al., J Mater Chem (2011) doi: 10.1039/C0JM01820A] is the first to show that solar cells that closely mimic nature can work effectively.

The team aim to fine-tune these water-based photovoltaic devices, making them even more like natural leaves. Lead author of the study, Dr. Orlin Velev, said “The next step is to mimic the self-regenerating mechanisms found in plants. The other challenge is to change the water-based gel and light-sensitive molecules to improve the efficiency of the solar cells.”

Although there is much still to be done before the devices could be sold commercially, the idea of biologically inspired soft devices that generate electricity could one day offer an alternative for current solid-state technologies, especially as they are more environmentally friendly and easier to dispose of when they reach the end of their natural life. However, it is important to show how they could be made more cheaply and on a larger scale than the current silicon cells.

The researchers, from NC State University, the Air Force Research Laboratory and Chung-Ang University in Korea, hope to expand their study to identify how to mimic the materials by which nature harnesses solar energy. To reach that point, as well as improving their efficiency, the team need to replicate the ability of natural leaves to regenerate and replace their organic dye. This would offer a solution to the problems of the long-term stability and performance typical of all organic photovoltaic devices.

This is a key advance for the future development of usable bio-mimetic devices – because of the photodegradation of the organic compounds in the devices, it is difficult to mimic the self-regenerating mechanisms found in plants and the decay of the light-sensitive molecules.