Making the most out of solar spectrum

Rice researchers selectively filtered high-energy hot electrons from their less-energetic counterparts using a Schottky barrier (left) created with a gold nanowire on a titanium dioxide semiconductor. A second setup (right), which included a thin layer of titanium between the gold and the titanium dioxide, did not filter electrons based on energy level. Credit: B. Zheng/Rice University

The progress in photovoltaic panels has been not as impressive as the one of general electronics (no Moore's law here) but has nevertheless managed to lower the cost of the panels to a point that they have become more and more affordable. Actually, if you were to consider just the cost of solar panels you might say that they are more cost efficient than coal burning (yet one of the most efficient way to generate electricity).

However in the total cost of generating electricity with photovoltaic systems the actual cost of the panels make up just 20% of the total cost. You need to consider other costs like the one of the real estate needed for the panels, the deployment.... and so on. 

Hence, even if we were to further decrease the cost of panels (as researchers are doing in India through "frugal innovation") the overall cost won't be affected that much.

This is why researchers are looking at ways to improve the efficiency of the solar panels that might result in decreasing the need of real estate space and the cost of deployment.

At Rice University they are exploring ways to increase the efficiency by using plasmonics (surface electrons). They are creating structures, see figure, that can convert more wavelength out of the solar spectrum.

At the University of California Riverside researchers are taking a different approach, still having in mind to harvest new portion of the solar light spectrum. They have discovered a way to capture two infrared photons (low energy photons having a wavelength in the infrared spectrum) and converting them into a higher energy photon that can be readily be absorbed by the photovoltaic panel.

They have managed to do this by creating hybrid solar panels inserting organic molecules (to pick up the low energy infrared photons) into the usual inorganic semiconductor nano-crystals forming today's solar panels.

We might expect to see more photovoltaic in the coming decade, and most of it in places where it would be unaffordable today. That will further increase the demand for a smarter grid to balance load and offering. Something EIT Digital is seriously working on.

Author - Roberto Saracco

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