Stories by Justine Brown

Portable plastic power

TECHNOLOGY PDAs, laptops and pocket calculators are essential for any CIO on the go. But when batteries run low, these tools become little more than excess baggage.
But what if you could power portable electronics anywhere you could access solar energy? That’s the scenario Paul Alivisatos and Janke Dittmer imagined. The two researchers at the University of California at Berkeley have developed a new generation of solar cells that combine nanotechnology with plastic electronics. Alivisatos and Dittmer say these semiconductor-polymer photovoltaic cells can be painted on just about any surface, allowing them to be made in an infinite variety of shapes. “If you have a pocket PC, it could have a small, flexible solar cell painted on the back of it,” says Dittmer. “When the batteries run low, you’d simply put it in the sun upside down to recharge it.”
The hybrid solar cells consist of tiny nanorods (composed of a material similar to that used in computer chips) suspended in plastic. The mixture is sandwiched between two electrodes, one composed of transparent plastic and the other of flexible aluminum.
Combining the flexibility of plastics with the electronic properties of inorganic semiconductors resulted in a cell with myriad potential uses. For example, while traditional silicon-based solar cells can be easily broken, the plastic-based cells can withstand much more abuse. “You could design a pocket calculator with a flexible solar cell, and it could take any shape — even round — and would be fully flexible,” Dittmer says.
The new cells also open up possibilities for wearable computing devices. “Because of their flexibility, it would be possible to put solar cells on clothing to power small computer processors,” says Dittmer.
The hybrid solar cells can be produced in a laboratory beaker without clean rooms or vacuum chambers, which means that they’ll eventually be cheaper and easier to make than traditional solar cells. However, they may still be several years away. Dittmer says their efficiency will have to be improved prior to being placed in a commercial product.

Written by Justine Brown31 Aug. 02 22:00