NMRL

  Organic light emitting diodes (OLEDs) are becoming increasingly important because of their applications for large area flat-panel displays and general lighting. The internal quantum efficiency of OLEDs have been achieved near 100% using electro-phosphorescent materials with proper management of singlet and triplet excitons, however, the external quantum efficiency of conventional devices remains near 20% because of losses due to wave-guiding effect. Recently, there has been great progress to enhance the light out-coupling efficiency of OLEDs by means of various internal and external device modification techniques. Microcavity effect, photonic crystals and nano-cavity, nano-particles, nano-structures and surface plasmonenhanced techniques are classified as internal light extraction technique. And substrate modification methods such as using high refractive index substrate, use of scattering medium, micro-lens arrays are classified as external light extraction technique. These techniques have been implemented to enhance the external extraction efficiency of OLEDs.