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10 April 2005 Numerical study on thickness dependence of passivation layer in top-emission organic light-emitting devices
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In this paper, we demonstrate simulation results of a top-emission organic light-emitting device (TOLED) with a passivation layer and a dielectric layer. Passivation layer is usually composed of silicon dioxide (SiO2) and/or silicon nitride (Si3N4) to protect organic layers from oxygen and moisture. Dielectric layer is a high refractive index thin film for enhancing the external quantum efficiency. The TOLED device has a microcavity structure which comprised of an opaque and high reflective anode and a thin semitransparent cathode. When varying dielectric layer thickness, the output intensity changes and the spectrum peak shifts. The peaks oscillate as a function of the dielectric thickness and the period is around hundreds of nanometers depending on the refractive index of the dielectric layer. When adding the passivation layer, which is on the order of micrometers, more than single peak are observed. With a simple model, we found that the frequency difference between two peaks corresponds to the free spectral range of the fabry-perot cavity formed by passivation layer. When a passivation layers is added on the TOLED, the microcavity effect results in the presence of multi-peaks. It limits the view angle and decreases the color purity.
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Chia-Chiang Shiau, Hung-Chi Chen, Jiun-Haw Lee, Yean-Woei Kiang, Chih Chung Yang, and Chih-Hsiang Chang "Numerical study on thickness dependence of passivation layer in top-emission organic light-emitting devices", Proc. SPIE 5740, Projection Displays XI, (10 April 2005);

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