One problem in developing more efficient organic LED light bulbs and displays for TVs and phones is that much of the light is polarized in one direction and thus trapped within the light-emitting diode, or LED. University of Utah physicists² believe they have solved the problem by creating a new organic molecule³ that is shaped like rotelle -- wagon-wheel pasta -- rather than spaghetti（意大利面条）. The rotelle-shaped molecule -- known as a "pi-conjugated spoked-wheel macrocycle" -- acts the opposite of polarizing sunglasses, which screen out（筛选） glare reflected off water and other surfaces and allow only direct sunlight to enter the eyes.

 

The new study showed wagon-wheel molecules⁴ emit light randomly⁵ in all directions -- a necessary feature for a more efficient OLED, or organic LED. Existing OLEDs now in some smart phones and TVs use spaghetti-shaped polymers -- chains of repeating molecular⁶ units -- that emit only polarized light.

 

"This work shows it is possible to scramble⁷ the polarization of light from OLEDs and thereby⁸ build displays where light doesn't get trapped inside the OLED," says University of Utah physicist¹ 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 perfectly⁹ symmetrical, and that makes the light it generates perfectly random," he adds. "It can generate light more efficiently¹⁰ because it is scrambling¹¹ 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 emphasizes the study is basic science, and new OLEDs based on the rotelle-shaped molecules are "quite a way down the road."

 

He says OLEDs now are used in smart phones, particularly the Samsung Galaxy¹² series; in pricey new super-thin TVs being introduced by Sony, Samsung, LG and others; and in lighting¹³.

 

"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 sensors¹⁴; they also have potential use in solar cells and switches, he adds.

 

The study was funded by the Volkswagen Foundation, the German Chemical Industry Fund, the David and Lucille Packard Foundation and the European Research Council.

 

Lupton is a research professor of physics and astronomy at the University of Utah and also on the faculty¹⁵ of the University of Regensburg, Germany. He conducted the study with Utah physics graduate student Alexander Thiessen; Sigurd Höger, Vikas Aggarwal, Alissa Idelson, Daniel Kalle and Stefan-S. Jester of the University of Bonn; and Dominik Würsch, Thomas Stangl, Florian Steiner and Jan Vogelsang of the University of Regensburg.

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