Monday, August 13, 2012

UCLA's new transparent solar film could be game-changer

One of the holy grails of solar cell technology may have been found, with researchers at UCLA announcing they have created a new organic polymer that produces electricity, is nearly transparent and is more durable and malleable than silicon.

The applications are mind-boggling. Windows that produce electricity. Buildings wrapped in transparent solar cells. Laptops and phones – or even cars or planes – whose outer coverings act as chargers. It might even be sprayed on as a liquid. The promise of cheap and easy-to-apply site-generated solar electricity might now be a lot closer to reality.

Of course, the idea of solar films and solar plastics is not new. The breakthrough to making a transparent film, however, came with isolating only one band of light in the spectrum.

“[A solar film] harvests light and turns it into electricity. In our case, we harvest only the infrared part,” says Professor Yang Yang at UCLA’s California Nanosystems Institute, who has headed up the research on the new photovoltaic polymer. Absorbing only the infrared light, he explains, means the material doesn’t have to be dark or black or blue, like most silicon photovoltaic panels. It can be clear. “We have developed a material that absorbs infrared and is all transparent to the visible light.”

“And then we also invented a new electrode, a metal, that is also transparent. So we created a new solar cell,” Yang adds.

Well, the metal is actually not transparent, Yang points out; it’s just so small that you can’t see it. The new polymer incorporates silver nanowires about 0.1 microns thick, about one-thousandth the width of a human hair, and titanium dioxide nonoparticles as an electrode. When in liquid form, it is as clear as a glass of water, and when applied to a hard, flat surface as a film it is meant to be invisible to the eye.

Thin-film PV currently exists that can be applied to windows, but only on windows that can be tinted. Many buildings use tinted windows as a way to cut down infrared radiation and thus keep out excess heat. Because this new transparent film is meant specifically to absorb in the infrared spectrum, it may be able to cut air conditioning bills and generate electricity at the same time, while leaving windows clear. Technically, however, the entire building could be covered with the thin film and not affect colors.

Isolating the infrared spectrum is currently a less-efficient way to make electricity, and Yang says his group’s technology converts about 6% of the sun’s energy into electricity, as opposed to 11% or 12% from commercial PV. But, he says, that can change. More


No comments: