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Solar Cells Could Capture Infrared Rays for More Power

Hybrid materials could boost photovoltaic efficiencies by 30 percent or more

1 min read
Images by Zhiyuan Huang/UC Riverside
Nanocrystals and organic materials convert low-energy photons into visible light that a solar cell can capture. Cadmium selenide nanocrystals with one kind of organic coating [left] produced violet light, while cadmium selenide nanocrystals with another type of organic coating [right] produced green.
Images: Zhiyuan Huang/UC Riverside

Solar cell efficiencies could increase by 30 percent or more with new hybrid materials that make use of the infrared portion of the solar spectrum, researchers say.

Visible light accounts for under half of the solar energy that reaches Earth's surface. Nearly all of the rest comes from infrared radiation. However, solar infrared rays normally passes right through the photovoltaic materials that make up today's solar cells.

Now scientists at the University of California, Riverside, have created hybrid materials that can make use of solar infrared rays. The energy from every two infrared rays they capture is combined or “upconverted” into a higher-energy photon that is readily absorbed by photovoltaic cells, generating electricity from light that would normally be wasted.

The hybrid materials are combinations of inorganic semiconductor nanocrystals, which capture the infrared photons, and organic molecules, which help combine the energy from these photons together into an upconverted photon. In experiments, lead selenide nanocrystals captured near-infrared photons, and the organic compound rubrene emitted visible yellow-orange photons.

The researchers noted that lead selenide nanocrystals and rubrene were relatively inefficient at upconversion. However, in experiments with a hybrid material made of cadmium selenide nanocrystals and the organic compound diphenylanthracene, which absorbs green light and emits violet light, the investigators could boost upconversion up to a thousandfold by coating the nanocrystals with anthracene, a component of coal tar. This suggests that similar coatings on lead selenide nanocrystals might boost their upconversion efficiency as well.

The scientists added that the ability to upconvert two low energy photons into one, high-energy photon has potential applications in biological imaging, high-density data storage, and organic light-emitting diodes (OLEDs). They detailed their findings online July 10 in the journal Nano Letters.

The Conversation (0)
This photograph shows a car with the words “We Drive Solar” on the door, connected to a charging station. A windmill can be seen in the background.

The Dutch city of Utrecht is embracing vehicle-to-grid technology, an example of which is shown here—an EV connected to a bidirectional charger. The historic Rijn en Zon windmill provides a fitting background for this scene.

We Drive Solar

Hundreds of charging stations for electric vehicles dot Utrecht’s urban landscape in the Netherlands like little electric mushrooms. Unlike those you may have grown accustomed to seeing, many of these stations don’t just charge electric cars—they can also send power from vehicle batteries to the local utility grid for use by homes and businesses.

Debates over the feasibility and value of such vehicle-to-grid technology go back decades. Those arguments are not yet settled. But big automakers like Volkswagen, Nissan, and Hyundai have moved to produce the kinds of cars that can use such bidirectional chargers—alongside similar vehicle-to-home technology, whereby your car can power your house, say, during a blackout, as promoted by Ford with its new F-150 Lightning. Given the rapid uptake of electric vehicles, many people are thinking hard about how to make the best use of all that rolling battery power.

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