Innovations in Solar Energy

Solar energy offers lots of promise for reducing our dependence on fossil fuels and cutting greenhouse gas emissions. In fact, some researchers say the sunlight hitting just 9 percent of the Mojave Desert in California could provide enough energy to power the entire U.S.

One of the hurdles still facing the technology, though, is the limited efficiency of today's solar cells. For all the sun energy that beams down onto Earth each day, solar cells still manage to convert only a small percentage into electricity. However, new discoveries and innovations are emerging regularly that could help us solve the solar cell efficiency problem.

Following are some of the most recent advances in solar cell efficiency:

Researchers at Northwestern University have found they can boost a solar cell's energy conversion rate by coating part of the cell with an ultrathin (5 to 10 nanometers thick) layer of nickel oxide. The process is not only inexpensive but can increase a solar cell's voltage by about 40 percent and improve the efficiency of energy conversion from the standard 3 to 4 percent to 5.2 to 5.6 percent.

Solar cell efficiency could be doubled by using silicon crystal coated with single-crystal layers of a semiconductor compound like gallium-arsenide, according to a discovery by two professors of engineering physics at McMaster University in Canada. The innovation has already generated a $4.1 million investment from the Ontario Centers of Excellence and ARISE Technologies Corp., a solar energy company.

A Swiss research team recently developed a solar cell that set a new record for energy conversion efficiency for a dye-sensitized cell. Dye-sensitized solar cells, which feature dye molecules on an electrode of titanium oxide, are typically inexpensive, easy to make and can have energy conversion efficiencies of more than 11 percent. However, the volatile compounds needed to make such cells mean they degrade quickly in outdoor conditions. The new Swiss innovation eliminates those volatile compounds, meaning it can remain stable and effective outdoors.

Researchers at the University of California, Santa Cruz, recently tested a combination of two methods for making nanotechnology-based solar cells (nanotechnology uses ultra-small particles in the size range of atoms and molecules.) The combo approach produced a solar cell that performed even better than expected. "We initially thought that the best we might do is get results as good as the sum of the two, and maybe if we didn't make this right, we'd get something worse," said Jin Zhang, a professor of chemistry. "But surprisingly, these materials were much better."

University of Copenhagen researcher Martin Aagesen believes a material called nanoflakes could be used to create solar cells with a sunlight-to-energy efficiency rate of 30 percent. He is working to develop such a solar cell as director of a company called SunFlake Inc.

Sandia National Laboratories and Stirling Energy Systems are developing a new-generation solar dish designed to have a much higher-than-normal energy conversion rate. On an exceptionally cold, bright day of testing in New Mexico this January, the dish achieved an efficiency rate of 31.25 percent, surpassing a 1984 record of 29.4 percent.

Saif Haque of Imperial College London is investigating ways to develop a hybrid, high-efficiency solar cell that uses both inorganic and organic semiconducting components. His research recently earned him the Royal Society of Chemistry's Edward Harrison Memorial Prize.

Scientists are exploring nanotechnology as a way to create solar cells that can capture the sun's energy as efficiently as photosynthesizing plants. One researcher, Nate Lewis at the California Institute of Technology, is studying a solar cell system that would mimic the way grass converts sunlight into energy.

Scientists at Durham University are working to develop solar cells that are thinner and much less expensive than traditional silicon-based photovoltaics. The thin cells could be made with materials like copper indium diselenide or cadmium telluride.

A team at the Fraunhofer Institute for Solar Energy Systems ISE are working on a nanomaterial-based, printable solar cell that could be produced in a variety of colors and even used to reduce glare on windows while generating electricity.