Solar technology improved

Solar

Yale researchers have developed cost-effective technology that increases the efficiency of solar cells.

In two papers published in the science journals Energy and Environmental Science and Nano Letters in December, the team of researchers details its new technology — hybrid solar cells made of carbon nanotubes and silicon. These cells — which convert sunlight to electrical energy more efficiently than traditional solar cells — are physically robust, flexible and “optically thin,” making them more suitable for a wider range of applications, said Kelsey Sakimoto ’12, a co-author of one of the papers.

“Our research bridges the cost-effectiveness of traditional organic solar cells with the efficiency of silicon,” said lead author Xiaokai Li GRD ’14, who studies in the Department of Chemical and Environmental Engineering.

Silicon-based solar cells are highly efficient due to silicon’s optical properties allowing it to absorb sunlight easily and convert it into energy, Li said. But processing silicon is costly and requires “extremely high” temperatures, he added.

In order to create their hybrid solar cell, the research team developed a low cost method that can be performed at room temperature. The researchers applied thin, smooth carbon nanotube films to silicon and then used an acid wash to dissolve the carbon, allowing the nanotubes to collapse together to form a highly conductive network, according to Andre Taylor, assistant professor of chemical and environmental engineering and a principal investigator of the study.

“The cell’s final structure is thin and therefore flexible,” Sakimoto said. “The cell is very strong and mechanically robust.”

In addition to improving the effectiveness of traditional solar panels, these solar cells may pave the way for innovative solar technology.

“Imagine your automobile if paint was a solar cell. We can integrate that with the new electric vehicle,” Taylor said. “Imagine rooftop shingles and other nonfunctional surfaces where you can integrate photovoltaic cells.”

Applications of the new technology are not limited to solar panels and solar-powered devices — the cells may be used in photodetectors, sensors and displays as well. These cells could also be used on various surfaces, not just those that are flat and square, said applied physics student Nitin Rajan GRD ’13, a co-author of one of the papers.

Taylor said his lab is currently carrying out further experiments to continue their thin-film research.

“This is a research project,” he said. “There’s always room for improvement.”

These improvements may include removing silicon from the equation.

Li said the team hopes to create pure carbon solar cells.

“Everyone knows about silicon. Carbon nanotubes are the mystery. Carbon nanotubes are very novel and have great potential in other applications,” he added.

The National Science Foundation, NASA, the U.S. Department of Energy and the Yale Institute for Nanoscience and Quantum Engineering provided support for the research.

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