This study demonstrates that attaching micro-lens array films (MAFs) on the substrate and reducing the substrate thickness of OLED can significantly increase the power efficiency, while simultaneously reduce image blurring. Using a point source model, based on Monte-Carlo ray-tracing method, the power efficiency enhancement and reduction of blur effect are respectively discussed in three different regions of the MAFs attached substrate: partially reflecting region, transmitting region, and light guiding region of micro-lenses. According to the equations, derived with regard to the substrate thickness and the displacement from the point source and based on geometric relations corresponding to different regions, reducing the substrate thickness will result in different levels of enhancement for power efficiency in different regions. By comparing OLED with MAFs and bare OLED, the overall enhancement ratio of power efficiency is 1.46, which can be further improved to 1.78 by reducing the substrate thickness from 700 μm to 50 μm, and the blurlength is reduced from 942 μm to 255 μm. The simulation results demonstrate the possibility of applying MAFs to OLED for higher power efficiency without image degradation in display and lighting applications.
To raise the speed of characterizing wafer-level LEDs, simultaneous measurement for both electrical and optical properties in parallel is a necessity. A non-imaging concentrator array is designed to concentrate as much light as possible from LEDs for optical characterization of multiple points on the wafer. For the sake of meeting the requirements between the numerical aperture of the sensing fiber and the emitting half-cone angle from a Lambertian source, a reversed angle transformer (RAT) is used in this study. The simulation is conducted using the commercial software LightTools® , based on the Monte-Carlo ray-tracing method. According to the simulation, the entrance port can collect approximately 94% of radiance from a Lambertian source, and the concentration ratio of RAT is approximately 99%. Finally a design prototype is demonstrated in this paper to validate our design.
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