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LighTimes: University of Utah Researcher Creates Rotelle-Shaped Organic Molecules that May Lead to More Efficient Organic LEDs

02 Oct 2013

October 1, 2013…University of Utah physicists have created a new organic molecule that does not polarize the light that it produces. Conventional organic LED molecules send out the light that the material emits in one direction because of polarization and the rest of the light is trapped in the material. This trapped light makes the OLEDs less efficient. However, Utah physicists believe they have solved the problem by creating a new organic molecule that is shaped like wagon-wheel pasta (rottelle) – rather than spaghetti.

Polarizing sunglasses allow light to enter the eye in only one direction. However, the rotelle-shaped molecule – known as a “pi-conjugated spoked-wheel macrocycle” emit light randomly in all directions. The researchers say that this is a necessary feature for a more efficient OLEDs

“This work shows it is possible to scramble the polarization of light from OLEDs and thereby build displays where light doesn’t get trapped inside the OLED,” says University of Utah physicist John Lupton, lead author of a study of the spoked-wheel-shaped molecules published online Sunday, Sept. 29 in the journal Nature Chemistry.

“We made a molecule that is perfectly symmetrical, and that makes the light it generates perfectly random,” he added. “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.”

Lupton points out that the study is basic science, and new OLEDs based on the new molecules are “quite a way down the road.”

He says OLEDs now are used in smart phones, particularly the Samsung Galaxy series; in pricey new super-thin TVs being introduced by Sony, Samsung, LG and others; and in lighting.

“OLEDs in smart phones have caught on because they are somewhat more efficient than conventional liquid-crystal displays like those used in the iPhone,” he says. “That means longer battery life. Samsung has already demonstrated flexible, full-color OLED displays for future roll-up smart phones.” Lupton says smart phones could produce light more efficiently using molecules that don’t trap as much light.

The large rotelle-shaped molecules also can “catch” other molecules and thus would make effective biological sensors; they also have potential use in solar cells and switches, he added.

The emitted light is blue-green, Lupton says, but images accompanying the paper – taken with a scanning tunneling electron microscope – show the rotelle- and spaghetti-shaped molecules with a false yellow-brown color for contrast.

Courtesy LIGHTimes News Staff