Scientists hope that installing a solar-powered electricity system in a home one day will be as easy as unfurling a roll of wallpaper on its roof.

Bernard Kippelen, associate professor at the University of Arizona's Optical Sciences Center, is working on material for a cheaper solar cell that is about one-thousandth as wide as a human hair.

Currently, solar power is too expensive for average people to power their whole house.

According to the U.S. Department of Energy, Americans pay about 20 to 30 cents per kilowatt-hour for electricity generated by the sun. This compares to 6 to 7 cents for traditional methods of generating electricity, such as burning coal.

"We're trying to develop a process that is low-cost, large-volume, and that is also non-toxic," said Kippelen, who just received a $490,000 grant from the Department of Energy to continue his work.

But in the Arizona team's work, led by Neal R. Armstrong, organic liquid crystals arrange themselves into conductive materials.

"You could spray paint or screen print a large area, and they would spontaneously assemble into a crystal," said Brian Gregg, a senior scientist at the National Renewable Energy Laboratory in Golden, Colo. Gregg published one of the first papers on the topic in 1986.

The crystals must be very well ordered for an electrical current to flow through them efficiently.

One of the main problems is getting the crystals to line up in the right direction.

"The perversity of nature is that they tend to line up in the wrong direction so the electrical conductivity goes in the wrong direction," Gregg said.

Kippelen said scientists still need to figure out how to make the materials stay stable for a long time. In addition, they now must use a liquid to carry the electrical charge, but the liquids eventually evaporate.

It may be 10 or more years before these materials hit the mainstream market.

"Basically we need a breakthrough," Gregg said. "You can't schedule these things and you can't predict them."

Other inorganic alternatives to silicon, such as cadmium and tellurium, can generate small amounts of toxic waste, Kippelen said.

But those products are farther along in development and could be about as thin as the organic materials, University of Central Florida Professor Neelkanth Dhere said.

Several plants in the country already are making thin-film solar panels using cadmium telluride.

"One cadmium (rechargable) battery certainly contains more cadmium than are in these cells. And the cadmium there is sort of contained so that it doesn't leach readily into landfills," said Dhere, who also is a principal scientist at the Florida Solar Energy Center in Cocoa.

Kippelen said NASA, too, could use the new technologies for lighter solar arrays.

NASA uses the sun to power many of its spacecraft. The International Space Station carries the largest solar arrays ever builtto provide electricity.

But Gregg said it is unlikely NASA will use the new technology because what's important in space is getting the most power possible, and the organic thin-films probably will never compete with traditional materials.

Kippelen also is working on optical lenses that could be changed with an electric pulse. In the future, people who now have bifocals could just hit a button on their spectacles to have the lenses change so they can look at things up close or far away.