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Engineers from the University of Michigan have created a new electrode that allows OLED panels to emit up to 20% more light. Researchers believe the breakthrough could help extend the battery life of smartphones and laptops that use screen technology. The technology could also make next-generation televisions and displays more energy efficient.
The researchers provided an approach that prevents light from getting trapped in the light-emitting part of an OLED, allowing them to maintain brightness and use less energy. The electrode is also easy to insert into an existing process for building OLED displays and lamps. University of Michigan researcher L. Jay Guo says the team’s approach allows for construction in the same vacuum chamber that is currently used.
According to the researchers, about 80% of the light produced by an OLED is trapped inside the device due to an effect known as a waveguide, unless engineers take action. This means that light rays that do not exit the device from an angle close to the perpendicular are reflected and guided laterally inside the device and are lost inside the panel. A large portion of the lost light is trapped between the two electrodes on either side of the light emitter.
Researchers say one of the biggest light traps is the transparent electrode that sits between the light-emitting material and the glass, usually made of tin and indium oxide. The engineers replaced the indium-tin oxide layer with a layer of silver only five nanometers thick deposited on a copper layer. The process allows the team to maintain electrode function by completely eliminating the waveguide in the OLED layers.
The team says the industry could free up more than 40% of the light by swapping conventional indium tin oxide electrodes for a nanoscale layer of transparent silver. The engineers note that although light is no longer guided into the OLED stack, the released light can still be reflected off the glass. Some researchers were able to release about 34% of the light using unconventional materials with special emission directions or pattern structures. The new design technology has a patent pending, and the researchers intend to commercialize the technology.
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