Researchers at Taiwan University in Taiwan, China, led by Professor Wu Zhongzhi, have developed a 3D pixel structure for OLED devices that can improve light extraction. The new design can increase the external quantum efficiency of the top light-emitting OLED device up to 30%.
The new design uses 3D reflective pixel structures filled with a graphically high refractive index material. The researchers created several pixels of different sizes and found that the smaller the pixel, the higher the efficiency gain.
To build the device, the researchers took advantage of the concave dike structure on traditional AMOLED pixels and modified the integration process so that the reflective bottom anode extends onto the pixel dike to form an optically reflective (but electrically isolated) pixel emitting region on the slope around the pixel. The high refractive index filler material further selectively fills the concave pixel region by vacuum evaporation through tiny openings in the aligned fine metal mask (FMM) to complete the reflective 3D pixel structure.
The researchers say greater efficiency gains can be achieved by further improving the 3D pixel structure, such as reducing optical losses by using a transparent top electrode.
