Dr. Orlin Velev, Invista Professor of Chemical and Biomolecular Engineering at North Carolina State University has shown that water-gel-based solar devices – “artificial leaves” – can act like photovoltaic solar cells to produce electricity. The findings prove the concept for making solar cells that more closely mimic nature. They 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.  Velev’s team 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.

Two photosensitive ions, DAS− and [Ru(bpy)3]2+, were used as the photoactive molecules embedded in the aqueous gel. The hydrogel photovoltaic devices showed performance comparable with or higher than those of other biomimetic or ionic photovoltaic systems reported recently. Velev’s team suggests a provisional mechanism, which is based on a synergetic effect of the two dye molecules makes the photocurrent power generation.

The team found an efficient replacement of the expensive platinum counter-electrode with copper coated with carbon materials, such as carbon nanotubes, carbon black or graphite. The copper electrodes coated with carbon layers could drastically reduce the cost of such hydrogel devices without efficiency loss. The NC team is showing a new class of low cost and flexible photovoltaic cells made of biocompatible matrix.

Water Gell Solar Cell. Click image for more info.

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, Dr. Orlin Velev said in describing this new generation of solar cells.

Velev says 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, Velev says naturally derived products – like chlorophyll – are also easily integrated in these devices because of their water-gel matrix.

With the concept working and proven up with a working model, Velev says the researchers will work to fine-tune the water-based photovoltaic devices, making them even more like real leaves.

Velev says, “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.”

Velev can imagine a future where roofs could be covered with soft sheets of similar electricity-generating artificial-leaf solar cells.  “We do not want to over promise 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,” Velev says. “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.”

This is great news.  An alternative to the glass covered solid-state type where heat is an issue and vulnerability to weather conditions rule locations is welcome – albeit subject to freezing it would seem.  Perhaps a freeze proof design could be worked work.

Photovoltaic has major limits in cost, cost to payback and risk from the environment.  If Velev can drive down costs, expand the weather range and get worthwhile efficiency the concept should have great market legs.

Velev’s team includes researchers from the Air Force Research Laboratory and Chung-Ang University in Korea who co-author the study published at the Journal of Materials Chemistry. The funding was from Air Force Research Laboratory and the U.S. Department of Energy.  It would be a good idea to keep the funding going.

A close reading of the press release and the study abstract shows Velev is trying to connect to photosynthesis.  With voltage output now proven one has to wonder what other compounds might be integrated which may create a multipurpose cell.  Getting some form of power and a perhaps a fuel product from a cell would be quite a change in perspective for solar cells.


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