Imagine being able to recharge a laptop, iPod or cell phone without having to plug a battery into the wall.

Now, UW scientists have created a prototype an organic polymer-based solar cell which may eventually lead to cheap, flexible and more environmentally-friendly energy alternatives.

"Typically, what's available in the market right now are solar cells, which are based on inorganic materials — usually they're Silicon — and these devices work really well, but it's actually really expensive, and the average household can't afford them," said Christine Luscombe, assistant professor of materials science and engineering. Luscombe also helped develop the new cell.

Traditional inorganic polymer solar cells must be processed in a vacuum-sealed environment in many steps, said Glenn Bartholomew assistant professor of chemistry. They also require high-temperature processing, Luscombe said.

Many high-efficiency cells also use Cadmium selenide (CdSe), a highly toxic compound. According to the Material Safety and Data Sheet, CdSe is harmful if touched, inhaled or ingested. It can cause cancer in humans and can be devastating to aquatic ecosystems.

Yet the team was able to use a cheaper, room-temperature manufacturing technique called solution processing to create a CdSe-free solar cell, according to the May 23 issue of Solar Energy Materials and Solar Cells. The researchers used the traditional structure of a CdSe solar cell, but replaced the toxic substance with an organic polymer called polybenzimidazobenzophenanthroline (BBL). To manufacture the chip, the team mixed the organic polymer with a solvent. They then placed it on a conducting transparent electrode, Luscombe said.

"Then you do this thing called spin coating," Luscombe said. "You have the electrode spinning really fast, and the drop of polymer solution just spreads out and makes a thin film. At the end, you evaporate metal electrodes on top, and that's it."

Though the means of creating the chip is nothing new, the researchers required a more recent addition to complete the procedure.

"The process itself has existed for 30 years or so, but the semi-conducting polymers are quite a new class of materials. Until they were discovered, we couldn't do things like solution processing," Luscombe said.

While the cell provides an exciting proof-of-concept, it must be at least twice as efficient to be commercially viable.

"The commercially-available ones have [an] efficiency of 13 percent," Luscombe said. "The highest efficiency we can currently get in a small device in a lab is 5 percent or 6 percent."

Even with these obstacles, some of the properties of the organic polymer cells make it an appealing option for eventual widespread use.

"Our efficiencies were very low, but we did accomplish high voltages, which is a problem with traditional inorganic solar cells," Bartholomew said.

Because of the material structure of organic polymers, they may also be more flexible than inorganic solar cells, he said. The organic polymer class of solar cells could potentially be rolled up for easy storage and portability.

Now, the group is focusing on ways to increase efficiency.

"We're looking at sensitizing our solar cells to the full range of the solar spectrum, further out to the red and infrared," Bartholomew said.

In addition, the devices aren't stable in air, so the group is researching other air-stable organic polymers, and cheap ways to encapsulate the existing polymer, Luscombe said.

Bartholomew estimated that it would take five years before solar cells like these might be viable for portable electronics. The U.S. Department of Energy has set a goal for commercially viable technologies to be created by 2020 or 2030, Luscombe said. But the rising price of energy may hasten the development of such technologies.

"Portable solar cells haven't been implemented because of the cost-per-watt of energy relative to petroleum," Bartholomew said. "As the price of oil continues to grow, they bring photo-voltaic alternatives closer and closer to market, simply on a cost-per-watt basis."

Reach columnist Tia Ghose at news@thedaily.washington.edu.