Improved outcoupling of light into substrate modes of an organic LED (OLED) by an ultra-low index of refraction (n=1.15), porous SiO(2) grid (UltraLIG) fabricated using glancing-angle deposition is demonstrated. Outcoupling into the substrate for electrophosphorescent tris(2-phenylpyridine) iridium [Ir(ppy)(3)]-based OLEDs grown on substrates with the UltraLIG is increased by 48% over a conventional device at a luminance of 100 cd/m(2). With efficient light outcoupling at the substrate-air interface, the UltraLIG devices attain eta(EQE)=22.5% and eta(P)=64 lm/W at their peak efficiencies, a nearly threefold increase over an analogous conventional OLED.
[Show abstract][Hide abstract] ABSTRACT: We present an analytical method for extracting the recombination zone location from emission patterns produced by organic LEDs (OLEDs). The method is based on derivation of the closed-form expressions for OLED-radiated power developed in previous work and formulation of the analytical relations between the emitter position and the pattern extrema. The results are confirmed to be in good agreement with reported optical measurements. The resultant formulae offer insight regarding the dominant physical processes in the device and can be utilized to assess or verify the location of the recombination zone, a very important parameter in the optimization process of OLED efficiency, from standard optical measurements, otherwise a very difficult task to achieve.
[Show abstract][Hide abstract] ABSTRACT: Light out-coupling efficiency of organic light-emitting devices from high-index glass substrate into air is enhanced by attaching ordered microlens arrays, which are fabricated by a roll-to-roll mold transfer process. The dependence of microlens geometries on light extraction is analyzed experimentally and theoretically. An increase of 60% in the light out-coupling with an optimized elliptical microlens array is achieved over a conventional device without affecting the electroluminescent spectrum.
[Show abstract][Hide abstract] ABSTRACT: Organic light emitting devices (OLEDs) have been used in flat-panel displays and lighting with a near-30-year development. OLEDs possess many advantages, such as full solid device, fast response, flexible display, and so on. As the application of phosphorescence material, the internal quantum efficiency of OLED has almost reached 100%, but its external quantum efficiency is still not very high due to the low light extraction efficiency. In this review the authors summarizes recent advances in light extraction techniques that have been developed to enhance the light extraction efficiency of OLEDs.
Guang pu xue yu guang pu fen xi = Guang pu 04/2011; 31(4):871-6. DOI:10.3964/j.issn.1000-0593(2011)04-0871-06 · 0.29 Impact Factor
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