Quantum process increases the number of electrons produced when light strikes a metal-dielectric interface.
Researchers at MIT and elsewhere have found a way to significantly boost the energy that can be harnessed from sunlight, a finding that could lead to better solar cells or light detectors.
The new approach is based on the discovery that unexpected quantum effects increase the number of charge carriers, known as electrons and “holes,” that are knocked loose when photons of light of different wavelengths strikes a metal surface coated with a special class of oxide materials known as high-index dielectrics. The photons generate what are known as surface plasmons — a cloud of oscillating electrons that has the same frequency as the absorbed photons.
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The team found that by varying the composition and thickness of the layer of dielectric materials (such as aluminum oxide, hafnium oxide, and titanium oxide) deposited on the metal surface, they could control how much energy was passed from incoming photons into generating pairs of electrons and holes in the metal — a measure of the system’s efficiency in capturing light’s energy. In addition, the system allowed a wide range of wavelengths, or colors, of light to be absorbed, they say.
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