Solar cell produces record voltage

A leap has been made by Irish and American scientists in developing clean, renewable fuels from sunlight and water.

They have designed a solar cell that produces a record-breaking voltage, bringing the possibility for electricity generated solely from sunlight a step closer.

Scientists from Tyndall National Institute in Cork, Queen’s University in Belfast, and Stanford University in California’s Silicon Valley have worked together on the project, tackling the challenge of developing a non-corrosive solar cell that can split water molecules without an outside power source.

A process called artificial photosynthesis can be used to split water into its constituent elements of pure oxygen and hydrogen. Hydrogen is a clean fuel that produces only water when burned. It can also be used to produce methane and methanol from reactions involving carbon dioxide.

Funneling carbon dioxide into reactors for transformation into fuel instead of releasing it into the atmosphere reduces its harmful effect on the global climate.

In 2011, researchers at Stanford University added a thin layer of titanium dioxide to the anode part of the solar cell to protect its surface from corrosion. A problem emerged because the protective layer meant that less light-induced voltage was generated by the silicone-based cell beneath.

Paul Hurley from Tyndall Institute found a way of boosting the voltage and a prototype that he made exceeded all expectations when it was sent to Stanford University for testing.

“The holy grail of water-splitting using solar cells is that you put them into water and just use solar energy to split the water molecules,” said Dr Hurley. “At Tyndall, we suggested adding a new layer of silicon doped with an excess positive charge between the original silicon cell and the protective layer.”

He said they wanted to create just a little more photo-voltage than what was achieved with one type of silicone. Not only was it found to be much better, it broke the record for the voltage produced by this type of anode. While the voltage from the newly-designed cell is not yet enough to split water, the record-breaking voltage opens the way for cells using the new design principles to be tested.

“At Tyndall, we are now examining different materials that can protect silicon, conduct electricity and be transparent enough to transmit light,” he said.

Dr Hurley believes it could take at least 10 years before the cell would be available commercially: “I think people should be very excited about the project. If you can just use sunlight to create oxygen and hydrogen, then you have a totally clean source of fuel. Carbon dioxide creates global warming and, if you can react hydrogen with carbon dioxide you can make natural gas — another source of energy.”

The impact of the development has been recognised in the peer-reviewed scientific journal Nature Materials. The Renew project (Research into Emerging Nanostructured Electrodes for the Splitting of Water), which will run until 2017, is partly funded by Science Foundation Ireland.