Let the Sun Shine In

I read an interesting article today in Science Magazine on a potential new solar cell design that could greatly enhance energy efficiency capture from sunlight. The method utilizes carbon nanotubes (CNTs) grown between two tiny electrodes, rather than large and expensive silicon wafers, to create the photovoltaic cell. When light strikes the silicon semiconductor in a traditional solar cell, one exciton is produced, which then moves towards an electrode creating a current. Any additional energy from the photon's absorption is given off in the form of heat. In the new CNT-based cells, studies indicate that the nanotubes are able to produce more than one exciton from a single photon absorption event, increasing the overall efficiency of the cell.
Sounds great, right? So what's the catch? The catch is that this phenomenon has only been observed so far at 60 degrees Kelvin, or around -213 degrees Celcius. But that's not all. Work so far has focused on characterizing the effect in a single cell. In order for this process to be applicable to, say, heating your home, the structure would have to be multiplied many billion times in an array. And on top of that, the production of the device would have to be scaled up to make it competitive with current solar panel production.

This is all very interesting and I found the article fascinating, but it reminded me of another solar cell innovation that was awarded as one of TIME Magazine's Best Inventions of 2008. The technology, which has matured to create the west coast-based company Nanosolar, is founded on the ability to 'screen print' the solar cell. Instead of using silicon wafers, Nanosolar uses semiconductor nanoparticles dispersed in a sort of ink, which is then printed onto a substrate very similar to aluminum foil. The result is an extremely thin, very lightweight, inexpensive solar panel. And when I say very lightweight, I mean VERY lightweight: check out the TIME article to see Nanosolar CEO Martin Roscheisen with a massive solar panel perched neatly on his shoulder. Currently, Nanosolar is targeting integration of the panels into energy grids in the form of solar 'power plants,' but the rest of us non-utility folk can sign up to receive updates on when their solar panels will become available to homeowners. I, for one, may be putting my name on that list.