University of Michigan researchers have created a new nanotech OLED electrode that could help extend the battery life of smartphones and laptops, or make next-gen televisions and displays much more energy efficient. The invention frees up 20% more light from organic light-emitting diodes.
Currently, about 80% of the light produced by an OLED gets lost and trapped inside the device due to an effect known as waveguiding where the light rays that don’t come out of the device at an angle close to perpendicular get reflected back and guided sideways through the device.
Guo and his team fixed this issue by replacing the transparent electrode that stands between the light-emitting material and the glass, typically made of indium tin oxide (ITO). They swapped it out for a layer of silver just five nanometers thick, deposited on a seed layer of copper, maintaining the electrode function while eliminating the waveguiding problem.
“Untreated, it is the strongest waveguiding layer in the OLED,” L. Jay Guo, U-M professor of electrical and computer engineering and corresponding author of the study, said in a statement. “We want to address the root cause of the problem.”
“Industry may be able to liberate more than 40% of the light, in part by trading the conventional indium tin oxide electrodes for our nanoscale layer of transparent silver,” added Changyeong Jeong, first author and a Ph.D. candidate in electrical and computer engineering.
Guo’s team then had to test whether they had successfully eliminated waveguiding altogether. They achieved this with an experimental set-up that allowed them to look at the contraption from the side and evaluate whether any light was still coming out sideways. They were happy to find out that the edge of the light-emitting layer was almost completely dark while the light coming through the glass was about 20% brighter. Mission accomplished! Now, it’s time to apply the new technology.