According to the researchers, about 80 percent of the light produced by an OLED is trapped within the device due to an effect called a waveguide, which means that light that does not exit the device from a near-vertical angle is reflected and guided within the device to the side and lost within the panel, with most of the lost light being trapped between the two electrodes on either side of the light emitter.
One of the largest light traps, the researchers said, is a transparent electrode, usually made of indium tin oxide, that stands between the light-emitting material and the glass. The engineers replaced the indium tin oxide layer with a silver layer just 5 nanometers thick, deposited on a copper seed layer. The process allowed the team to maintain electrode functionality while completely eliminating waveguides in the OLED layers.
The team said that by exchanging traditional indium tin oxide electrodes for nano-scale transparent silver layers, the industry can liberate more than 40% of the light. The engineers pointed out that although light is no longer guided in the OLED stack, the freed light can still be reflected off the glass. Some researchers have used unconventional materials with special emission directions or patterned structures that emit about 34 percent of the light. A patent has been filed for the new design technique, and the researchers intend to commercialize the technology in the future.