The electrical components responsible for lighting smartphone displays and flat-screen TVs, commonly referred to as LEDs, waste energy trying to make screens bright.
In an effort to solve this problem, physicist John Lupton from the University of Utah and his colleagues decided to change the material that LED bulbs are made of and, more importantly, their shape. Their findings, published in the journal Nature Chemistry, shows how they made LED molecules shaped like wagon-wheel pasta rather than their typical spaghetti-like shape.
Whereas the usual rod-shaped LEDs can trap up to 80 percent of light generated because light flows from them in only one direction -- known as polarization -- Lupton and his team made a molecule that is "perfectly symmetrical, and that makes the light it generates perfectly random,” he said in a university news release, noting the new organic molecule is known as OLED.
“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 lightbulbs that are more efficient and cheaper to operate,” Lupton said.
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The wagon-wheel LEDs -- known as a “pi-conjugated spoked-wheel macrocycle” -- have already left the lab and are being used in electronics, particularly the Samsung Galaxy series and the new super-thin TVs being introduced by Sony, Samsung and LG, Lupton noted.
“OLEDs in smartphones have caught on because they are somewhat more efficient than conventional liquid-crystal displays like those used in the iPhone,” he said, describing the six-nanometer-wide molecule. “That means longer battery life.”
“The rotelle -- technically called oligomers -- are basically wrapped-up polymers,” Lupton said. “They all have the same shape, but they do not emit polarized light because they are round. They generate waves that vibrate in all directions. The light doesn’t have a fixed polarization; it doesn’t vibrate in a fixed direction. It always can get out.”
While more work has to be done with OLEDS to understand their true capacity, Lupton said, “In principle, we should be able to double the efficiency of getting the light out.”
“Even if we scramble the polarization, we’re always going to have a bit of light trapped in the OLED,” he said. “Those losses are now 80 percent, and we probably could get down to 50 or 60 percent.”