A quantum dot may be tiny, but this development has the potential to be quite big.
Researchers at the University of Toronto have developed a new form of photovoltaic material using "quantum dots" -- confined sets of electrons with unusual optical and electronic properties -- embedded into a thin polymer film. The material can generate the photoelectric effect using infrared light, and is the first photoelectric polymer to have significant infrared sensitivity. When working across infrared and visual spectra, it has a photoelectric efficiency of 30% -- six times better than other polymer photovoltaics. 30% efficiency would make quantum dot polymer solar cells competitive with traditional silicon-and-glass panels, and far more functional. Quantum dot polymer material could be used in device cases, and Ted Sargent, one of the researchers responsible for this development, claims that the material could readily be spray-applied or painted on.
"We made particles from semiconductor crystals which were exactly two, three or four nanometres in size. The nanoparticles were so small they remained dispersed in everyday solvents just like the particles in paint," explains Sargent. Then, they tuned the tiny nanocrystals to catch light at very long wavelengths. The result – a sprayable infrared detector.
As this suggests, the implications of the discovery are broader than just photovoltaics. The quantum dot polymers have a sensitivity to infrared which will be of enormous value in medical imaging, fiber optic communications, and sensor technologies. As the polymer could be readily woven into fabric, it could enable better wearable biosensors, and would definitely be an enabling technology for fabric computers. The big win, of course, would be the possibility of an easily-added solar power layer to the external shell of any device using electricity. It doesn't have to replace plug-in power completely to be a significant efficiency improvement.
The research will be published in the February 2005 edition of Nature Materials, but is now available for download by subscribers. A summary can be found here, along with supporting graphics and materials (free subscription required).
This also appeared on Slashdot, but the discussion had a lot of caveats. One, that your writeup misses, is that the 30% figure is highly theoretical and NOT here "real soon". Specifically, the referenced article says:
Our calculations show that, with further improvements in efficiency, combining infrared and visible photovoltaics could allow up to 30 per cent of the suns radiant energy to be harnessed,..." Note the words "calculations", "could allow" and "up to". This might be a breakthrough, but don't hold your breath.
While the 30% represents a theoretical value even a 10% efficiency would be huge for one reason... cost. Current PV technology is expensive because the manufacturing process requires a lot of energy and expensive materials. The resulting panels are heavy and installations are labor intensive. This results in a cost per kilowatt hour that is not very competitive with other sources of energy (at least no without incentives or feed-in tarriffs). However, thin sheets of this stuff can be manufactured using roll-to-roll technology common in the film manufacturing industry (or news paper printing for that matter) and the cost per watt has the potential to be significantly lower than traditional silicon based PV.