Researchers are using two types of “designer” quantum dots for producing double-pane solar windows, capable of generating electricity with greater efficiency and developing insulation and shading for good measure.
It is all made possible with the help of a new window architecture, which employs two varied layers of low-cost quantum dots tuned for absorbing varied parts of the solar spectrum.
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. The approach complements existing photovoltaic technology by adding high-efficiency sunlight collectors to existing solar panels or integrating them as semitransparent windows into a building’s architecture.
Victor Klimov, Lead Researcher
“Solar-spectrum splitting” is considered to the key to this advance and it permits one to process separately lower- and higher–energy solar photons. The higher-energy photons can produce a greater photovoltage, capable of enhancing the overall power output. This method also enhances the photocurrent as the dots employed in the front layer are essentially “reabsorption free.”
To attain this, the Los Alamos team integrates ions of manganese into quantum dots and these manganese ions act as greatly emissive impurities. Light absorbed by the quantum dots triggers these impurities. The manganese ions, following activation, emit light at energies below the quantum-dot absorption onset. This trick permits for almost total elimination of losses because of self-absorption by the quantum dots.
In order to transform a window into a tandem luminescent sunlight collector, the Los Alamos team deposits a layer of copper indium selenide quantum dots onto the surface of the back pane and a layer of greatly emissive manganese-doped quantum dots onto the surface of the front glass pane. The front layer then absorbs the ultraviolet and blue portions of the solar spectrum, while the bottom layer picks up the rest of the spectrum.
After absorption, the dot re-emits a photon at a longer wavelength, and this is followed by guiding the re-emitted light by total internal reflection to the glass edges of the window. There, solar cells included into the window frame gather the light and transform it to electricity.
Publication: Kaifeng Wu, Hongbo Li, and Victor I. Klimov, Tandem luminescent solar concentrators based on engineered quantum dots, Nature Photonics, DOI 10.1038/s41566-017-0070-7, January 1, 2018.
Project members: Kaifeng Wu (Director’s Postdoctoral Fellow), Hongbo Li (Postdoctoral Research Associate, Victor I. Klimov (Laboratory Fellow, Project Leader).
Acknowledgements: This research was supported by the Center for Advanced Solar Photophysics (CASP), an Energy Frontier Research Centre funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences