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March 29, 2002 WASHINGTON (Reuters) --
Cheap, plastic solar cells that can be painted onto just about any surface could provide power for a range of portable and even wearable electronic devices, scientists said on Thursday.
A team at the University of California Berkeley said they had come up with a first generation of plastic solar cells, which could someday replace the bulky and expensive silicon-based cells used widely now.
"Our efficiency is not good enough yet by about a factor of 10, but this technology has the potential to do a lot better," Paul Alivisatos, a professor of chemistry who led the study, said in a statement.
"There is a pretty clear path for us to take to make this perform much better."
Alivisatos and his team, reporting in the journal Science, said they had created a hybrid solar cell, made of tiny nanorods dispersed in plastic. Sandwiched between electrodes, the hair-thin layer produces about 0.7 volts, they said.
They can be made "quick and dirty" in a laboratory beaker without the need for clean rooms or vacuum chambers, the researchers said.
"Today's high-efficiency solar cells require very sophisticated processing inside a clean room and complex engineering to make the semiconductor sandwiches," Alivisatos said. "And because they are baked inside a vacuum chamber, they have to be made relatively small."
"The beauty of this is that you could put solar cells directly on plastic, which has unlimited flexibility," added Janke Dittmer, who also worked on the study.
"This opens up all sorts of new applications, like putting solar cells on clothing to power LEDs (light-emitting diodes), radios or small computer processors."
PHILIP BALL, 9 February 2001
The Hubble Space Telescope is powered by the sun. But solar power comes at a price. Now a new plastic solar cell three times more efficient at converting light to electricity than previous cells of its kind could bring cheap 'green' energy down to earth.
The obstacles to the widespread use of solar power are price and efficiency. The most effective solar cells are made from expensive materials, and their cheaper counterparts fail the productivity test.
But Sean Shaheen at the Johannes Kepler University in Linz, Austria, and co-workers have found a ray of hope. They have designed a plastic cell with an efficiency that they say "approaches what is needed for the practical use of these devices for harvesting energy from sunlight".
Although they are potentially cheap, lightweight and flexible, solar cells made using plastics have so far proved to be too inefficient -- at less than one per cent -- to be commercially viable.
One way to make solar panels affordable is to make them capture more sunlight for the same panel area. Another option is to make them from inexpensive materials -- even relatively inefficient devices might be commercially viable if they are dirt cheap to make.
Many believe that plastic solar cells will one day be cheap and efficient enough to mass-produce for use in solar panels -- not just for high-tech space science but for powering entire cities.
Almost all of today's commercial solar cells, known as photovoltaic cells, are made of thin, rigid sheets of silicon, or alloys of silicon with other semiconducting materials. The best of these are about 20 per cent efficient -- they convert about one fifth of the incident sunlight into electricity. But standard commercial panels are typically only half as efficient.
The Austrian team found a way to boost the performance of existing plastic cells by mixing a conducting polymer, MDMO-PPV, with a molecule PCBM made from the carbon football, buckminsterfullerene.
The researchers get round the fact that these two materials tend to segregate like oil and water by using the solvent chlorobenzene instead of toluene -- that other researchers have been using -- to get a very even blend of the two components.
"These results," the researchers say, "demonstrate that organic photovoltaic devices can be a viable technology for future power generation."