White OLED Emission Stack Layout for Better Viewing Angle
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing display apparatuses face issues with white balance and color temperature due to lower luminous efficiency of blue emission material layers, leading to deteriorated luminance and color tone when viewed from oblique directions.
Innovation Solution
A display apparatus with a light-emitting layer comprising four emission stacks and charge generation layers, where one emission stack has a stacked structure of red and blue emission material layers, and the second, third, and fourth emission stacks include blue, green, and blue emission material layers respectively, improving light extraction efficiency and color purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the second electrode has high reflectance to improve light extraction efficiency, then light extraction efficiency is improved, but phase change of light increases with distance causing rapid reduction in luminance and color tone in oblique directions
Solution Approach 1:
The light-emitting layer is divided into multiple emission stacks (first, second, third, fourth emission stacks) with different emission materials. This segmentation allows each stack to contribute differently to the overall light output, improving color balance and viewing angle characteristics while maintaining high light extraction efficiency through the reflective second electrode.
Solution Approach 2:
Different emission stacks are positioned at different locations within the light-emitting layer, with each stack having specific emission characteristics (red, green, blue emissions). This local differentiation of emission properties enables improved color uniformity and viewing angle across the display area while utilizing the high-reflectance second electrode.
2Illumination intensity
If blue emission material layer is used, then blue light is emitted, but luminous efficiency is lower than red and green emission material layers causing degraded white balance and color temperature
Solution Approach 1:
Multiple emission stacks emitting different colors (red, green, blue) are combined within the same light-emitting layer. The blue emission from the fourth stack compensates for the lower luminous efficiency of blue materials, while the combined output of all stacks achieves balanced white light emission with improved color temperature and white balance.
Solution Approach 2:
The light-emitting layer uses a composite structure with multiple emission material types (red emission material, green emission material, blue emission material) arranged in separate stacks. This composite approach allows optimization of each material's contribution to achieve overall balanced color output and improved energy efficiency.
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
The proposed solution enhances the white balance and color temperature of the emitted light, improving overall luminance and image quality, especially when viewed from different angles.
Implementation Method 1
The light-emitting layer generates light displaying a white color. The light-emitting layer includes four emission stacks and charge generation layers.
Implementation Method 2
when the second electrode of each light emitting device has a relatively high reflectance to improve light extraction efficiency
Data Source
AI summary
A light-emitting device includes a light-emitting layer between a first electrode and a second electrode, he light emitted from the light-emitting device may display a white color, the light-emitting layer may include a plurality of emission stacks, each of the emission stacks includes at least one emission material layer, one of the emission stacks may include a stacked structure of a red emission material layer and a blue emission material layer, thus improving the white balance and increasing color viewing angle.