Suppression of the color shift of microcavity organic light-emitting diodes through the introduction of a circular polarizer with a nanoporous polymer film

A circular polarizer (CP) film modified by a nanoporous polymer film (NPF) was applied to improve the viewing angle characteristics of a top-emission organic light-emitting diode (TEOLED) without any serious pixel blur phenomenon. From this approach, the angular color shift (Δu′v′) was significantly improved from 0.096 to 0.056, and the angular luminance distribution was also expanded to the Lambertian distribution direction. The black color had a slightly faded tint, however, like the turn-off condition of the plasma display panel (PDP), regardless of the introduction of NPF below or above the CP. Very interestingly, the surface reflectance of the device with NPF-coated CP was not significantly different from that of the device with non-NPF CP. The pixel blur level according to the distance between the scattering medium and the light source was also investigated. As a result, it was found that the pixel blur phenomenon can be greatly suppressed by applying a thinner encapsulation lid with an NPF film.