Wagon-wheel Molecule Shape Emit Light More Efficiently

Researchers have developed a wagon-wheel shaped molecule far more effective at emitting light than typical light-emitting diodes (LEDs).

Because LEDs are generally shaped like long strings, much of the light becomes polarized and thus trapped. When this happens, the light fails to reach the viewer.

In the new study, researchers developed a wagon-wheel shaped molecule that emits light randomly in all directions -- a feature that scientists say is necessary for more efficient OLEDs, or organic LEDs.

"We made a molecule that is perfectly symmetrical, and that makes the light it generates perfectly random," John Lupton, lead author of the study, said in a statement. "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."

Though the research is still in the beginning stages, theoretically the new type of molecule should double the efficiency of light emission over the string-shaped LEDs, according to the scientists.

"We made a molecule that is perfectly symmetrical, and that makes the light it generates perfectly random," Lupton said. "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."

OLEDs are currently used in some smart phones, including the Samsung Galaxy series. However, many of the OLEDs in use are made with "pi-conjugated polymers," plastic-like, organic semiconductors, which Lupton calls a "terrible mess."

"They now make only mediocre OLEDs, although people like to claim the opposite," he said, pointing to their trapping of up to 80 percent of the light generated as evidence.

The new molecule is a direct response to this shortcoming.

"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," he said.