Varying Optical Distances in OLED Color Conversion
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Solution Overview
Problem
The existing display apparatus using a color conversion layer for organic electroluminescent devices has low efficiency in converting blue light to red light, which reduces the overall light emission efficiency and extraction intensity for blue and green subpixels.
Innovation Solution
The display apparatus is configured with varying optical distances between the light-emitting layer and the reflective electrode layer for different subpixels, allowing for optimal light extraction whether with or without a color conversion layer, thereby increasing color conversion efficiency without reducing light emission intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a yellow light-emitting component is added to blue light-emitting devices to increase red conversion efficiency, then the conversion efficiency for the red conversion layer increases, but the light emission energy is scattered to two types of light emission (blue and yellow), thereby reducing the light emission efficiency for the organic electroluminescent device itself and reducing the light extraction intensity for subpixels of emitted blue and green lights
Solution Approach 1:
The patent applies local quality by providing color conversion layers selectively to specific subpixels rather than uniformly to all light-emitting devices. Green subpixels are equipped with green color conversion layers while red subpixels receive red color conversion layers, allowing each subpixel to be optimized for its specific color conversion needs without unnecessary energy scattering from unwanted conversion layers.
Solution Approach 2:
The patent segments the color conversion function by dividing the display into separate subpixels (green and red) that each have their own dedicated color conversion layers. This segmentation prevents the energy scattering problem by ensuring that blue light is converted only to the intended color in each subpixel region, maintaining overall light emission efficiency while achieving high conversion efficiency for each color channel.
2Illumination intensity
If a color conversion layer is provided on blue light-emitting devices to convert blue light to red or green, then the extracted color light intensity increases, but the optical distance must be precisely optimized to derive interference for emitted lights, which complicates the manufacturing process
Solution Approach 1:
The patent employs parameter changes by systematically varying the optical distance between the light-emitting layer and reflective electrode layer to achieve constructive interference for the converted color lights. By optimizing this optical parameter, the patent enhances extracted color light intensity through interference effects while establishing clear manufacturing guidelines for achieving the desired optical performance.
3Productivity
If the optical distance between the light-emitting layer and reflective electrode layer is optimized for direct blue light extraction, then blue light extraction intensity is maximized, but this optimization does not necessarily optimize the optical distance for converted color lights when color conversion layers are present
Solution Approach 1:
The patent resolves this contradiction by applying local quality optimization - different optical distances are provided for different subpixel types. Blue subpixels use one optical distance optimized for direct blue light extraction, while green and red subpixels use different optical distances optimized for their respective color conversion and extraction, allowing each subpixel type to achieve maximum performance for its specific function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the color conversion efficiency and light extraction intensity for all colors, maintaining high light emission efficiency and eliminating the need for precise metal mask coloring in manufacturing.
Implementation Method 1
The color conversion layer serves to absorb the emitted blue lights, and use fluorescence or phosphor or combination thereof to make the absorbed blue lights glow in red or green
Implementation Method 2
The color conversion layer serves to absorb the emitted blue lights, and use fluorescence or phosphor or combination thereof to make the absorbed blue lights glow in red or green
Implementation Method 3
the optical distance is optimized between the light-emitting layer and the reflective electrode layer to derive interference for emitted lights generated by the light-emitting layer of the blue light-emitting device
Data Source
AI summary
A display apparatus that includes: a plurality of light-emitting devices disposed on a substrate with an accumulation of, in this or inverse order, a light transmissive electrode layer, a functional layer including a light-emitting layer, and an opposing electrode layer; and a color conversion layer that is provided on a side of the light transmissive electrode layer for any of the light-emitting devices, and applies color conversion to an emitted light generated by the light-emitting layer for the light-emitting device. In the display apparatus, the light-emitting devices each have a reflective surface on a position where the light-emitting layer is sandwiched with the light transmissive electrode layer, and an optical distance between the reflective surface and the light-emitting layer varies by the light-emitting devices depending on provision of the color conversion layer.