High refractive index nanoparticle material was applied as a scattering layer on the inner side of a glass substrate of a bottom emission organic light emitting diode (OLED) device to enhance light extraction and to improve angular color shift. TiO2 and YSZ (Yttria Stabilized Zirconia; Y2O3-ZrO2) were examined as the high refractive index nanoparticles. The nanoparticle material was formed as a scattering layer on a glass substrate by a coating method, which is generally used in the commercial display manufacturing process. Additionally, a planarization layer was coated on the scattering layer with the same method. The implemented nanoparticle material and planarization material endured, without deformation, the subsequent thermal annealing process, which was carried out at temperature ranged to 580 °C. We demonstrated a practical and highly efficient OLED device using the conventional display manufacturing process by implementing the YSZ nanoparticle. We obtained a 38% enhanced luminance of the OLED device and a decreased angular color change compared to a conventional OLED device.

A top emitting organic light-emitting diode (OLED) device with pure aluminum (Al) anode for high-resolution microdisplays was proposed and fabricated. The low work function of the Al anode, even with a native oxide formed on the Al anode surface, increases the energy barrier of the interface between the anode and hole injection layer, and has poor hole-injection properties, which causes the low efficiency of the device. To enhance the hole-injection characteristics of the Al anode, we applied hexaazatriphenylene hexacarbonitrile (HATCN) as the hole-injection layer material. The proposed OLED device with a pure Al anode and native oxide on the anode surface improved efficiency by up to 35 cd/A at 1000 nit, which is 78% of the level of normal OLEDs with indium tin oxide (ITO) anode.