Researchers at an American national laboratory have now employed quantum dots for double-pane solar windows that offer shading, insulation, and, of course, generate energy – with greater efficiency. The Los Alamos National Laboratory team drew on a new window architecture utilizing two layers of low-priced quantum dots, tuned to take in distinct parts of the solar spectrum.
The double-pane windows were equipped with manganese-doped quantum dots, absorbing blue and ultraviolet, on the surface of the front glass pane, and copper indium selenide quantum dots, absorbing the rest of the spectrum, on the back pane’s surface. Once light is absorbed, dots re-emit it at a longer wavelength. Total internal reflection guides the light to the edges, where it can be gathered and turned into power by solar cells in the window frame.
Solar-spectrum splitting – in which higher- and lower-energy solar photons can be processed separately – is key to the research, according to Los Alamos. And the dots in the front layer are essentially reabsorption free, which the laboratory said the team accomplished by incorporating into quantum dots manganese ions “that serve as highly emissive impurities. Light absorbed by the quantum dots activates these impurities. Following activation, the manganese ions emit light at energies below the quantum-dot absorption onset. This trick allows for almost complete elimination of losses due to self-absorption by the quantum dots.”
The journal Nature Photonics published the research online on New Year’s Day. Per the article’s abstract, the researchers’ prototype “exhibits a high optical quantum efficiency of 6.4 percent for sunlight illumination and solar-to-electrical power conversion efficiency of 3.1 percent. The efficiency gains due to the tandem architecture over single-layer devices quickly increases with increasing LSC [luminescent solar concentrator] size and can reach more than 100 percent in structures with window sizes of more than 2,500 centimeters squared.”
Double-pane quantum dot solar window research could lower the cost of solar power, according to lead researcher Victor Klimov, who said in a statement, “Because of the strong performance we can achieve with low-cost, solution processable materials, these quantum-dot-based double-pane windows and even more complex luminescent solar concentrators offer a new way to bring down the cost of solar electricity.”