Light Efficiency Improvement of Organic Light-Emitting Devices by Optimizing Thickness of Organic Layers and Parameters of Micro-Pyramid Array Films
Date Issued
2010
Date
2010
Author(s)
Huang, Chung-Ying
Abstract
We optimize the source apodization of organic light-emitting devices (OLEDs) with micro-pyramid array films for solid state lighting. To discover the relationship between the source apodization and the base angle of micro-pyramid array films, we calculate the organic emitter apodization with different thicknesses of Alq3 layer from electromagnetic theory, and simulate micro-pyramid array films are attached on top of OLEDs by using ray-tracing method. Moreover, we use the high-refractive-index substrate and truncated micro-pyramid array in order to enhance the luminous power and normal-direction luminous intensity. In general, when the base angle equals to 60 degree, the luminous power ratio is the highest; when the base angle equals to 45 degree, the luminance ratio is the highest. When Alq3 layer is thicker, the angular FWHM is larger, and the luminous power and luminance ratio is higher. Besides, when the angular FWHM is large and the refractive index of substrate is high, we must use micro-pyramids of large base angle to enhance more normal-direction luminous intensity. The best coupling efficiency 56% is that OLEDs with the micro-pyramid array for Alq3 thickness of 90 nm when the refractive index of substrate is 1.72.
Truncated micro-pyramid array films further enhance the luminous power and luminous intensity of OLEDs. When the fill factor equals to 1.0, the half-height micro-pyramid array has the best luminous power enhancement; besides, we use the truncated micro-pyramid array with the height which is higher than three quarters of full-height in order to enhance the luminous intensity.
Subjects
OLEDs
source apodization
micro-pyramid array films
high-refractive-index substrate
truncated micro-pyramid
Type
thesis
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