Solar Cell Absorption Rates, Reaching Near-Perfect

One key to improving solar cell efficiency has been to improve the cells’ ability to absorb sunlight at all, let alone convert that radiation to electricity. Historically, absorption rates have created competition between different manufacturers of solar cells. Thin-film, CdTe cells, for example, have very high absorption rates, but are less efficient in other ways. Yet that race to be better than the competition may eliminate any competition in that regard in the near future as scientists are now claiming the accomplishment of near perfect solar absorption rates. An uncoated, traditional silicon solar panel absorbs about 67% of the sunlight colliding with it. Cadmium Telluride (CdTe) cells can absorb up to 90% of the solar spectrum but, again, are less efficient at conversion than silicon cells, essentially nullifying any advantage. Other second and third generation solar cells show similar characteristics. All absorption rates for solar cells also depend on the angle of the sunlight colliding with the cells. The advent of nanotechnologies however, promises to greatly increase the absorption rate of several if not all of those solar cell materials. Scientists at Renssalaer Polytechnic Institute recently announced successful tests with a new nano-coating that can vastly increase absorption rates. This antireflective coating captures a much higher amount of photons, enabling solar panels to absorb the entire spectrum of sunlight regardless of the sun’s position in the sky. Silicon panels tested with the nano-coating consistently reached absorption rates of over 96%. So the question of which solar cell absorbs more photons across a broader spectrum may soon be rendered moot by nanotechnology; once again putting the focus on conversion efficiency and manufacturing expense.

Posted on January 21 in Solar Information by .

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