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Spray On Solar Power Cells

Ted Sargent is a pioneer in solar technology. He has been working on a spray-on solar cell. The implications for our energy systems are profound. As Ted says, "Solar energy is not just an exciting science problem, but an incredibly important human problem."

Ted is working on solar nanotechnology with the potential to make solar energy very cheap and allow society to collect it on a huge scale. Currently, solar technology costs more to build and install than most people are willing to pay. Solar panels, for example, the technology most commonly associated with solar energy, are installed on your rooftop. The cost of collecting one kilowatt per hour of solar energy (about a third of the electricity an average household uses on any given day) is about $11,000.

Not only are panels expensive to install, they capture only the visible portion of the sun's rays so they work only on sunny days. Ted's focus is the infrared portion of the sun's rays which accounts for more than half of all solar energy. What's more, infrared energy is available to us even in cloudy weather.

A quantum dot is a semiconductor nanostructure that confines the motion of conduction band electrons, valence band holes, or excitons (bound pairs of conduction band electrons and valence band holes) in all three spatial directions.

The confinement can be due to

• electrostatic potentials (generated by external electrodes, doping, strain, impurities),
• the presence of an interface between different semiconductor materials (e.g. in core-shell nanocrystal systems),
• the presence of the semiconductor surface (e.g. semiconductor nanocrystal), or
• a combination of these.

A quantum dot has a discrete quantized energy spectrum. The corresponding wave functions are spatially localized within the quantum dot, but extend over many periods of the crystal lattice. A quantum dot contains a small finite number (of the order of 1-100) of conduction band electrons, valence band holes, or excitons, i.e., a finite number of elementary electric charges.

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