Design of optical compensation film for improving the optical performance of organic light emitting diodes

The organic light emitting diode (OLED) display is one of the most promising devices among next-generation information displays because of the advantage of optically clear self-emitting characteristics. Nevertheless, in the conventional OLED display device, the luminous efficiency is increased by using a metal electrode having a high reflectance in the cell, but due to the reflection characteristic in the cell from the incident of external light, the dark characteristic is deteriorated and the contrast characteristic is dramatically reduced. In order to overcome this disadvantage, we propose an optical configuration consisting of a polarizer, quarter-wave plate (QWP), and C-plate for wide-band and wide-view performance, which mean high contrast in visual wavelength range and viewing angle in terms of polar and azimuthal angles while maintaining the transmittance characteristics of OLED when external light is incident. To designing an optimized optical configuration, the phase differences of light were calculated with trigonometric method and polarization characteristics were analyzed using a Poincaré sphere when passing through each optical film. To verify the optical performance of the proposed optical configuration, we applied it to OLED devices through experiments, as a result we confirmed that optical performance could be improved in terms of wide-band and wide-view without disturbing with the transmittance of OLED device.