Physicists at the U believe they have found a way to increase the efficiency of LED lightbulbs.
The secret lies in the shape of the molecules that emit the light. Light is produced when molecules move up and down. In most phone and TV screens, the light-emitting molecules are shaped like spaghetti noodles, known as chain polymers. Because of their shape, they polarize light in only one direction. The new molecule, which is called a “pi-conjugated spoked-wheel macrocycle,” is similar in shape to a wagon wheel and will allow the light to be emitted in every direction since the molecule is perfectly symmetrical.
“For the rings, all possible polarization’s can exist since they are round. It’s like a string vibrating in all directions,” said John Lupton, a professor of physics and astronomy and lead author of the study. “Every time you excite the ring, a photon is emitted from a different, random, segment of the ring.”
The study about the molecules was published Sept. 20 in the Journal of Natural Chemistry.
The new wagon-shaped molecule could mean more efficient organic LEDs, or OLEDS. Organic LEDs are different from regular LEDs because they use organic materials, like the hydrocarbons used to make plastic bags instead of materials consisting of crystals like gallium nitride. OLEDs have the potential to be more efficient than tradition LEDs and this added efficiency can have impacts on things such as cell phone battery life.
“The wagon wheel shape provides more order to the molecule, giving it a round shape that allows emission of light without a preferred orientation of the polarization,” said Alexander Thiessen, a graduate research assistant in the College of Science. “OLEDs have the potential to be cheaper in production [than LEDs]”.
LEDs, known as light-emitting diodes, are a type of solid state lighting that emits light that is generated by the material itself. This is different from the common incandescent light bulb because incandescents use a filament that glows inside the light source. The effect created by solid state lighting is called wave guiding, which is when the solid state material guides the light similar to how an optic fiber would.
“You can see wave guiding effects for example on the reflection of light from water surfaces, or in a mirage,” Lupton said.
Lupton said that by depolarizing the light, they may be able to make OLEDs more efficient as less light is trapped in the device.
“We’ve only demonstrated the depolarization effect, which is new,” Lupton said.