Hot electrons can double solar cell efficiency

Solar cell that captures hot electrons - Michael Naughton
Solar cell that captures hot electrons - Michael Naughton
“Hot electrons” are created when a high energy photon (i.e. sunlight) hits a solar cell.   In most solar cells, however, these hot electrons lose most of their energy as heat before it passes through the cell and generates electricity, so much of the energy is lost.   But now a physics professor at Boston College, Michael Naughton, has come up with 15 nanometer ultra thin solar cells that capture these hot electrons.   There have been previous solar cell designs  that could capture hot electrons, but in doing so, they couldn’t also capture and use lower power photons.   Dr. Naughton’s new design can capture both kinds, potentially leading to much higher efficiency solar cells and a much lower cost per kilowatt.

Theoretically, the new design can lead to high efficiency solar cells of up to 67% – conventional high efficiency silicon based solar cells can convert only about 35% of the sunlight into electricity, while the rest of the energy is wasted as heat.  There’s still lots to be worked out with these new cells – because they’re so thin, much of the sunlight passes right through.   But the team wants to utilize other research that shows that adding nanowires to the solar cells will allow them to absorb more light.   They’re also exploring the possibility of adding quantum dots to the nanowires to further increase the amount of electrons absorbed from light.

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