Wheel-Shaped Molecules Make Better Displays

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Light-emitting diodes are so common we never give them a second thought. They’re responsible for lighting up the displays in many smartphones and flat-screen televisions. But typically LEDs are made from molecules that are shaped like long strings that encourage light to become polarized and get trapped, drawing down efficiency. As a result, big chunk of the light that LEDs emit doesn’t reach the viewer, which means power is wasted trying to keep the display bright.

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Physicist John Lupton from the University of Utah and his colleagues, including scientists from the University of Bonn decided to solve this problem by changing the material LEDs were made of. They used molecules shaped like wagon wheels to create organic LEDs, also called OLEDs. The research appears in the journal Nature Chemistry.

The wheel shape, Lupton noted in a press release, emits light randomly, ensuring that the light does not become trapped.

“We made a molecule that is perfectly symmetrical, and that makes the light it generates perfectly random,” he said in the press release. “It can generate light more efficiently because it is scrambling the polarization. That holds promise for future OLEDs that would use less electricity and thus increase battery life for phones, and for OLED light bulbs that are more efficient and cheaper to operate.”

That means less power is needed to make the display bright enough to see. and because the light is not polarized, a screen would be easier to read in daylight.

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There’s still some work to do before we see this kind of OLED in the latest smartphone screens. Lupton said the study is still fundamental research, rather than technology development. And there are other possibilities as well — such organic molecules could find their way into some types of solar cells. They might even make good sensors, because the wheel-like shape allows them to catch other molecules like a net.

Credit: Stefan Jester, University of Bonn

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