Thursday, 11 July 2013

Organic polymers show sunny potential
29 May 2013

( new version of solar cells created by laboratories at Rice and Pennsylvania State universities could open the door to research on a new class of solar power devices.

The photovoltaic devices created in a project led by Rice chemical engineer Rafael Verduzco and Penn State chemical engineer Enrique Gomez are based on block copolymers, self-assembling organic materials that arrange themselves into distinct layers. They easily outperform other cells with polymer compounds as active elements. The discovery is detailed online in the American Chemical Society journal Nano Letters.

While commercial, silicon-based solar cells turn about 20% of sunlight into electricity and experimental units top 25%, there's been an undercurrent of research into polymer-based cells that could greatly reduce the cost of solar power, Verduzco said. The Rice/Penn State cells reach about 3% efficiency, but that's surprisingly better than other labs have achieved using polymer compounds.

"You need two components in a solar cell: one to carry (negative) electrons, the other to carry positive charges", Verduzco said. The imbalance between the two prompted by the input of energy-sunlight-creates useful current.

Since the mid-1980s, researchers have experimented with stacking or mixing polymer components with limited success, Verduzco said. Later polymer/fullerene mixtures topped 10% efficiency, but the fullerenes-in this case, enhanced C-60 buckyballs-are difficult to work with, he said.

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