06/27/2011 01:47

Organics could be cheap alternative to silicon in solar panels, says expert.
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While far less absorptive then the inorganic silicon panels currently used across the globe to transform the sun’s rays into useable energy, organic materials are extremely inexpensive and might provide an effective alternative to silicon in the near future, Prof. Stephen Forest of the University of Michigan argued at Ben-Gurion University in Beersheba on Monday.

Forrest was speaking at the 2011 Ilse Katz Institute Day, held at the university’s Ilse Katz Institute for Nanoscale Science and Technology, during a portion of the conference that focused on nanotechnology’s relation to renewable energy production.

In his talk, titled “Understanding and Controlling Solar Energy Conversion: The relationship between nanostructure and efficiency,” Forrest explained in technical detail the current experiments of his laboratory and the possibilities of using organic materials – which can be a wide variety of lightweight, recyclable plastics – in place of the heavier-duty, pricey silicon that is used in most solar fields and panels today.

“The materials are very, very inexpensive, and you can produce those on plastic foils – you can think of printing on a printing press,” Forrest told The Jerusalem Post after his talk.

“Organics give you an infinite amount of materials,” said Prof. Yuval Golan, director of the Institute for Nanoscale Science and Technology, lauding the low price and high versatility of these plastics. “They open a world of material opportunities.”

Unlike the heavier silicon, the organics could be produced in thousands of square-meters per day, and are so light that they could be wrapped around something like an aluminum foil roll, according to Forrest.

Due to the material’s nimbleness, however, it would probably be best attached to a building for stability, instead of standing alone on a vast field, he explained.

“You probably wouldn’t put it on a solar field as a plant generator,” said Forrest, who is also vice president for research at the University of Michigan.

While not always stable in aggressive sunlight, however, Golan argued that the organic materials will “be so cheap that you can replace them.”

The biggest problem with replacing silicon and amorphous silicon with organic materials is the current inability of these plastics to absorb sunlight at as high a level as their inorganic counterparts, according to Forrest.

“I think the best silicon on the lab-top is about 24 percent and the best amorphous is about 12% because it’s so disordered,” Forrest told his audience.

In the field, he later explained to the Post, that 24% translates to about 16%- 17%, while the 12% becomes 6%. The organic materials have the potential to reach a range of 21%-27% absorption rate in the lab, but they are not there yet, according to Forrest.

“If you can make organics really cheap, they become interesting at 7%-8%,” he said.

Forrest said that he would bet that within two years, scientists would develop organic solar cells capable of 10% absorption, and in four to five years, ones capable of 15% absorption.

While not quite up to silicon standards, he acknowledged, “for really cheap materials that’s a pretty good number to have.”

Forrest estimated that the world will begin to really see these materials emerge as a useable solar technology in about five years, but that it is still impossible to predict in exactly what mode, and in what places around the world.

“This is still a very immature technology, so we will start finding niches,” Forrest said, adding that perhaps the material could be used on windows, which currently contain a special coating that absorbs 50% of the heat coming through them. “Why not have it absorb light and produce electricity?” he asked.