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Quantum dot and 'dark state' tech in solar cells could boost efficiency

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Two new ways of capturing solar energy could make multiple exciton generation, or capturing more than one electron from a single photon, a practical reality. One group has demonstrated a solar cell that captures slightly over one electron per photon, and the other has discovered a "dark state" that could theoretically double the amount of electrons captured with current methods.

MEG Cell
MEG Cell

Two new breakthroughs in solar power may let us capture energy that was previously lost as heat. A National Renewable Energy Laboratory team has built the first solar cell capable of exciting more than one electron with a single photon, known as multiple exciton generation or MEG. Their method uses tiny semiconductor fragments called quantum dots, which can capture electrons separately. The idea of using the dots for solar cells isn't new, but until now remained only a theory. If adopted commercially, it could greatly increase the amount of power collected with a solar panel, and the NREL says it could even reduce costs enough to make solar power competitive with fossil fuels or nuclear power.

Meanwhile, a second group at The University of Texas at Austin is investigating a second method of electron capture. They have discovered that a light particle has a quantum "shadow state" that could be harnessed to double the amount of electrons captured. What's more, their hypothesized method could work with raw sunlight, rather than the focused beam used in their previous research on solar cells.

While neither of these methods will be ready for commercial application any time soon, they're a big step forward in making solar power a practical and widespread alternative to fossil fuels. Both groups' papers can be found in the most recent edition of Science.