Sometimes in science the answer is right in front of your nose the whole time. Like, say, when the issue of limitations in a solar technology can be addressed with, of all things, light.
Over the past several years, perovskite compounds have garnered increased interest around their potential as the basis of solar cells – though some inherent defects have limited their efficiency. New research announced this morning by MIT, however, reveals that the answer to the limitations of the compounds could be found in the most handy of places: really intense light.
This research comes as companies are looking to bring versions of the material to market within the year.
There are still some issues to overcome with the fix, the largest concern being how to maintain its effects over an extend period to make it worth manufacturers’ while. This research comes as companies are looking to bring versions of the material to market within the year.
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An experimental solar cell created by MIT researchers could massively increase the amount of power generated by a given area of panels, while simultaneously reducing the amount of waste heat. Even better, it sounds super cool when scientists talk about it: “with our own unoptimized geometry, we in fact could break the Shockley-Queisser limit.”
The Shockley-Queisser limit, which is definitely not made up, is the theoretical maximum efficiency of a solar cell, and it’s somewhere around 32 percent for the most common silicon-based ones.
You can get around this by various tricks like stacking cells, but the better option, according to David Bierman, a doctoral student on the team (and who is quoted above), will be thermophotovoltaics — whereby sunlight is turned into heat and then re-emitted as light better suited for the cell to absorb.
Sound weird? Here’s the thing. Solar cells work best with a certain wavelength of light — perhaps ultraviolet is too short, while infrared is too long, but let’s say 600nm (orange visible light) is perfect. Only some of the broad-spectrum radiation emitted by the sun is at or around 600nm, which limits the amount of energy the cell can pull out of that radiation — that’s one of the components of the Shockley-Queisser limit.
What Bierman and the others on his team did was to add a step between the sun and the cell: a carefully engineered structure of carbon nanotubes. “The carbon nanotubes are virtually a perfect absorber over the entire color spectrum,” said Bierman in the MIT news release. “All of the energy of the photons gets converted to heat.”