Solar Paint and Other Solar Surprises

A doctoral student with UC Berkeley's interdisciplinary Energy and Resources Group, Wadia came back to school after six years in business. He spends long hours in the lab "synthesizing super-small nanoparticles" in a three-necked flask.

The technique is so simple, he says, "anyone who feels comfortable in a kitchen could do it." These particles, less than a billionth of a meter in diameter, are then suspended in solution.

Wadia coats his solution on glass and analyzes his new device for "photocurrent," - the current that flows through a photosensitive device as the result of exposure to radiant power

The current occurs due to the photovoltaic effect that powers the common solar cells seen on rooftops across the United States. These photovoltaic arrays to convert light from the Sun directly into electricity.

Nanotech solar cells are only a few years old. At the University of Toronto in 2005, electrical and computer engineering professor Ted Sargent announced that he had developed a new plastic nanotech material containing solar cells. The Berkeley research takes the technology a step farther.

Through his nanotech experiments, Wadia hopes to identify a material that is "extremely cheap, non-toxic, and abundant" in nature and suitable for manufacturing photovoltaic cells. Such a material "may not exist," he admits, "but we have to try."

"Nanomaterials, because we do them in solution, we could use that solution as a dye," Wadia says. "You could be looking at a wall that’s yellow, but that yellow is solar paints."

Traditional silicon based photovoltaic, PV, cells have been around for decades, but they are fragile, heavy, and costly.

Now solar is hot as Berkeley researchers attempt to bring solar technology to the next level, some by improving "first-generation" silicon-based PV, others by developing entirely new light-converting technologies.

"In the past few years, student interest has risen dramatically in all energy-related matters, especially photovoltaics," observes Eugene Haller, professor of materials science and engineering. "Many of the best applicants to our graduate program want to work in this field."

Materials science and engineering PhD student Becca Jones is researching exotic materials such as indium gallium nitride, a semiconductor material that shows promise for use in long-lived and highly efficient solar cells. Indium gallium nitride is the light-emitting layer in blue and green light emitting diodes, or L-E-Ds.

"Coupled with inexpensive mirrors or lenses," says Jones, these devices could focus "a lot of light on a very small solar cell."

Jones co-founded Students for Greener Berkeley and helped win student approval last spring of a $5 per semester fee increase to fund projects to "green" the campus.

Postdoctoral researcher Lucas Wagner, a quantum physicist who does theoretical studies of nanostructure systems for PV applications, says, "It's interesting science, and you feel you can face yourself when you go home at night."

Solar-cell researchers from across campus meet twice a month at midday to discuss their research problems, experiments, findings, and frustrations. Launched in spring 2006, the grad student-run PV Idea Lab has grown from about 10 initially to a regular cast of up to 30. Free lunch helps. But the main draw is highly technical and stimulating conversation in which issues like ohmic contact and semiconductor band-bending figure large.

"It's very directed and very driven, because we all want to solve the same problem, and we can help each other," Wadia says. With representatives from eight different teams now in the room, "it's really starting to feel like a multi-lab collaboration."

Copyright Environment News Service (ENS) 2007. All rights reserved.