Transparent Dyes Allow Windows to Act as Super-efficient Solar Panels

Special transparent dyes coating glass or plastic panes concentrate the Sun’s rays, guiding them to solar-voltaic cells lining the edges, allowing a window to act as a solar panel with 10 times the electricity generation capacity of solar cells, by current standards. The ‘organic solar concentrator’ (OSC) system also reduces cost, by reducing the surface area that needs to be coated by solar-voltaic cells and by eliminating the need for large concentrating mirrors and sun-tracking mechanisms.

According to the journal Science, where the findings were published:

Light is absorbed by the coating and reemitted into waveguide modes for collection by the solar cells. We report single- and tandem-waveguide organic solar concentrators with quantum efficiencies exceeding 50% and projected power conversion efficiencies as high as 6.8%. The exploitation of near-field energy transfer, solid-state solvation, and phosphorescence enables 10-fold increases in the power obtained from photovoltaiccells, without the need for solar tracking.

The Economist is using the term ‘luminescent solar concentrator’, and notes that the work reported by Michael Currie and Jonathan Mapel of the Massachusetts Institute of Technology (MIT) is being researched elsewhere as well, and is related to the standard functioning of fiber optic technologies, which concentrate light and contain it within a conductive glass or plastic fiber. The OSC system conducts light toward the edges of the glass or plastic pane, trapping photons within the pane, causing it to seek out the high-efficiency solar-voltaic cells at the panel’s edge.

There are technical complications with perfecting the OSC system for harvesting solar energy. The dyes capture and concentrate the incoming sunlight, but an excess of dye molecules may prevent a quantity of light from reaching the circumferential solar cells, either by re-absorbing the light or by allowing heat to accumulate and losing the energy through that concentration of heat on the dyed surface.

The EE Times reports that the “edge-mounted” solar cells could receive light concentrated as much as 40 times. With the extreme heightening of efficiency, and the attendant reduction of costs, related to the new panels’ lack of need for mirrors or solar tracking mechanisms, the MIT advance could revolutionize the role of solar power in the global energy economy.

The dye-based solar concentrators could be on the commercial market within three years, distributed widely and helping homeowners and businesses establish productive capacity in linking up with the spreading renewables grid. Consumers with solar and wind-generation capacity can earn money on energy fed back into the local electricity grid.

The solar concentrating dye-coating can also be applied to exiting solar cells, heightening their light-capturing capability by as much as 30%, according to the MIT team. Marc Baldo, an MIT engineer, says “We think that ultimately this approach will allow us to nearly double the performance of existing solar cells for minimal added cost.”

While obstacles to containing and harvesting the full amount of energy captured by the dyes are an issue, Baldo’s team went far beyond previous attempts at increasing the efficiency of solar cells with the dye-retransmit method, by coating only the surface of a glass pane with the dyes, mimicking techniques used to improve the efficiency of lasers, which also contain and bounce light to intensify the retransmission of light at the other end of the contained space.

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Originally published July 11, 2008, on the HotSpring Network

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