The recent spate of solar cell improvements and efficiency upgrades has been rapid and unrelenting, with records broken and innovations achieved on an almost daily basis.
This is not surprising given the sudden boom in the sector following generous FiTs (feed-in-tariffs) and investments via governments and host nations, such as Germany or the UK. With money finally flowing in, the science of solar efficiency and panel production has skyrocketed, with similarly impressive new technologies becoming available to the general public. I love it.
The latest in the line of ingenious innovations, heralds from the University of California, Berkeley, and is certainly the most counterintuitive approach to the subject we’ve yet seen. The clever pair Eli Yablonovitch and Owen Miller have devised a way of creating solar cells which emit light, as well as absorbing it, using tried and tested LED technology. Yep, solar panels emitting light, and it works apparently.
According to the company subsequently set up to employ the new method in solar panels, Alta Devices, based in San Fran constructed prototype cell with efficiencies of 28.3% for a single-junction cell, breaking the current record (yet another). They went on to build the first solar panel, which was verified at 23.5% efficiency by the National Renewable ENergy Laboratory, breaking yet more records; panels retain lower efficiencies due to the extra bits shoved in to make the thing. Not bad for a piece of tech which seems to go against its original purpose of collecting light.
So How Does This Actually Work - What Magic Is Involved?
It would appear that when such solar panels begin emitting light efficiently, the voltage of electricity generated increases, therefore becoming better at its job, according to Eli Yablonovitch, the principal researcher and a Berkeley professor.
As solar cells have a known ceiling of efficiency sitting around 40%, making the most of what can be converted is key. This limit is due to the amount of light energy which is convertible under the physical laws of the material being used, with the theoretical efficiency of typical crystalline cells just 30%. This is pretty damn close to the Berkeley cell mentioned earlier.
What is also known relatively well, is that luminescent emission and voltage are a pretty comfy pairing, but this had never been applied to solar technology. By stopping extra electrons which aren’t being actively converted from getting ‘lost’ within the crystalline structure, voltages increase, and that’s the simple crux of it. Improving other aspects of the cell which aid these lost electrons in finding their way also ramps up generation, such as increasing the rear mirror reflectivity, which sends photons back out of the cell.
Considering this technology can be applied to pretty much all solar panels out there, it’s a huge leap forward in the solar race. We could be just years away from 3D, LED-emitting solar cells which absorb well over 90% of incident light (a.k.a the black cells recently developed) and achieve efficiencies at the very edge of theoretical ranges.
Then there would be no need for any of that dirty fossil fuel jazz right?