Top-emission organic light emitting diodes with lower viewing angle dependence

We obtained nanoporous polymer film which has 20-30% optical haze to suppress the viewing angle dependency of a top emission organic light emitting diode (TOLED) with strong microcavity effect. We controlled the sizes and density of nanopores by changing the spin coating condition such as spinning duration and spin rate in highly humid atmosphere up to 90% relative humidity condition. The resultant nanoporous polymer film has effectively reduced viewing angle dependency of microcavity TOLEDs without any serious decrease in total intensity of out-coupled light observed from the integrating sphere although the luminance observed from the front side was diminished slightly. Despite its negative effect on the efficiency toward the front direction, we could use those nanoporous polymer films as scattering media or diffuser layer on top of the encapsulation glass because it could change the strongly directed emission toward desired emission with Lambertian distribution. (C) 2014 Elsevier B.V. All rights reserved.