Carbon nanotubes stand at the forefront of solar cell technology. Subsequently, they are still embedded in the research and experimental phase. Carbon nanotube solar cells are extremely small. In fact, "small" is not a small enough word to describe them. A single-walled carbon nanotube, as developed by researchers at Cornell University, is about the size of a DNA molecule.
Nanotubes are narrow. Relative to width, they can be extremely long. According to Wikipedia, most single-walled nanotubes (think tiny, rolled up sheets of carbon molecules) are about one nanometer thick, or one billionth of a meter. This one nanometer-wide tube can be millions of times longer.
When light is shined onto the carbon nanotube, electrons are efficiently excited. These electrons are drawn down the tube by electrical contacts at either end. What makes nanotubes so special is that as the electrons flow down the nanotube, they get more excited and subsequently excite more electrons, which are uniformly "squeezed" out the end of the tube. These Cornell researchers have determined that carbon nanotubes may be the ideal photovoltaic cell because they allow excited electrons to create even more electrons, thus harnessing more of the photon energy from the light striking the tube.
In solar cells in use today, that excess energy is lost as heat. Not so with carbon nanotubes. Even more exciting is that these solar cells are working this efficiently on a miniscule level. The potential for creating a lot of energy from a very small space is there. The only problem now is how to scale the technology up to commercial size easily and inexpensively.
And now we're back to the same issue currently facing all promising solar cell technologies. A lot can happen under controlled laboratory environments, but translating that to an affordable, efficient and durable commercial product is very difficult.
That, however, is not going to get solar researchers down. There is no defeatist attitude in solar technology... the prospects are way too exciting. And carbon nanotube solar cells are on the front lines of excitement. Recent findings show that carbon nanotubes could someday constitute the perfect solar cell; they represent the ideal base to work from, and all good things are built from the bottom up.
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