OLED White Emission Layer with Tuned Capping Layers
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Solution Overview
Problem
Existing organic light emitting diode (OLED) displays require complex patterning technology to deposit separate color emission layers, which complicates manufacturing and limits resolution, especially for fine-sized subpixels.
Innovation Solution
The use of a white emission layer on all subpixels with a common electrode and a color filter layer, along with capping layers having different refractive indices and thicknesses for each subpixel area, optimizes light extraction efficiency and reduces color shift with viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate color emission layers are deposited in each subpixel area, then color emission performance is improved, but manufacturing complexity increases and resolution is limited
Solution Approach 1:
The patent merges the color emission function into a single white emission layer that covers all subpixel areas, eliminating the need for separate red, green, and blue emission layers. This white emission layer is combined with a color filter layer that provides color separation, thereby simplifying the manufacturing process while maintaining color emission performance.
Solution Approach 2:
The patent introduces a color filter layer as an intermediary component between the white emission layer and the external environment. This color filter layer mediates the white light from the emission layer to produce the desired red, green, and blue colors in respective subpixel areas, avoiding the complexity of depositing separate color emission layers.
2Ease of manufacture
If a white emission layer is used on all subpixels, then manufacturing is simplified, but light extraction efficiency and color purity may be compromised
Solution Approach 1:
The patent applies local quality by positioning capping layers with different refractive indices over different subpixel areas (red, green, blue). Each capping layer is specifically designed with refractive index and thickness optimized for its corresponding color wavelength, thereby improving light extraction efficiency for each color while maintaining the manufacturing simplicity of a single white emission layer.
3Power
If capping layers with different refractive indices are used for each subpixel, then luminous efficiency is improved, but device structure becomes more complex
Solution Approach 1:
The patent utilizes parameter changes by varying the refractive index and thickness of capping layers according to the specific wavelength requirements of different colors. The first capping layer has a refractive index of 2.7-3.6 for red light, while the second and third capping layers have refractive indices of 2-3 for green and blue light respectively. This parameter optimization improves luminous efficiency without requiring fundamentally different structural approaches.
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 luminous efficiency for red, green, and blue light, improving image quality and reducing color variation with angle, while simplifying the manufacturing process by eliminating the need for fine patterning of individual color emission layers.
Implementation Method 1
At least two capping layers among the plurality of capping layers have any one of a refractive index and a thickness different from each other
Implementation Method 2
a color filter layer including a plurality of filter layers corresponding to each of the plurality of subpixel areas
Data Source
AI summary
An organic light emitting diode display includes a substrate including a plurality of subpixel areas, a plurality of pixel electrodes positioned corresponding to each of the plurality of subpixel areas on the substrate, a white emission layer formed on the plurality of pixel electrodes; a common electrode covering the white emission layer, a plurality of capping layers positioned corresponding to each of the plurality of subpixel areas on the common electrode, and a color filter layer including a plurality of filter layers corresponding to each of the plurality of subpixel areas. At least two capping layers among the plurality of capping layers have any one of a refractive index and a thickness different from each other.