Organic Light Emitting Device with Reflection Decreasing Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Top emission type organic light emitting devices face challenges in achieving desired white light emission due to micro-cavity effects caused by semi-transparent cathodes, leading to color accuracy issues and reduced light efficiency.
Innovation Solution
Incorporating a reflection decreasing layer on the cathode, specifically for the white subpixel region, and varying the thickness of the anode in red, green, and blue subpixel regions to control optical lengths and minimize micro-cavity effects, along with a cathode design featuring regions with different light transmittance rates to enhance light efficiency and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a semi-transparent cathode is used in a top emission type organic light emitting device, then light can be emitted to the upper side, but micro-cavity phenomenon occurs causing color accuracy problems and reduced light efficiency
Solution Approach 1:
The cathode is divided into multiple regions with different light transmittance rates: a first region (corresponding to RGB subpixels) with higher light transmittance and a second region (corresponding to white subpixel) with lower light transmittance. This segmentation allows each region to be optimized for its specific function, preventing micro-cavity effects in the white subpixel region while maintaining efficient light emission in RGB regions.
Solution Approach 2:
Different regions of the cathode are assigned different optical properties (light transmittance rates) according to their specific requirements. The first region has higher transmittance for efficient light extraction in RGB pixels, while the second region has lower transmittance to suppress micro-cavity effects in white pixels. This local differentiation resolves the contradiction between overall light emission and local color accuracy.
2Device complexity
If a semi-transparent cathode is used to emit light upward, then the device structure is simplified, but light efficiency is reduced due to repeated reflections
Solution Approach 1:
The cathode's light transmittance is optimized locally for different pixel types. The first region has higher transmittance to maximize light extraction efficiency in RGB pixels, while the second region has lower transmittance to minimize energy loss from repeated reflections in white pixels. This maintains the simplified top-emission structure while improving overall light efficiency.
3Manufacturing precision
If the anode thickness is varied in different subpixel regions, then micro-cavity effects can be controlled, but manufacturing complexity increases
Solution Approach 1:
The anode thickness is differentiated locally: a first thickness in RGB subpixel regions and a second thickness (different from the first) in the white subpixel region. This local variation allows precise control of optical path lengths to manage micro-cavity effects, while the patent acknowledges this increases manufacturing complexity. The benefit of color accuracy outweighs the fabrication challenge.
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 solution effectively reduces micro-cavity effects, improves color accuracy, and enhances light efficiency and power consumption in organic light emitting devices, particularly in the white subpixel region, thereby extending the device's lifespan.
Implementation Method 1
micro-cavity phenomenon naturally occurs in which some portion of light emitted from the organic emission layer is repeatedly reflected by the cathode and the anode
Implementation Method 2
the light of a predetermined wavelength can be amplified by the constructive interference
Data Source
Figure 1a~1b
Figure 1c~1f
Figure 2a~2b
AI summary
An organic light emitting device utilizing the micro-cavity effect in the RGB subpixel regions while suppressing the micro-cavity effect in the white subpixel region is provided. The organic light emitting device includes a lower substrate, an anode formed on the lower substrate, an organic emission layer formed on the anode, a cathode formed on the organic emission layer, and a reflection decreasing layer formed on at least a portion of the cathode for reducing reflection of the light emitted from the organic emission layer by the cathode to reduce the micro-cavity effect. Such a selective use of the micro-cavity effect in the organic light emitting device improves the color accuracy, the luminance efficiency and the lifespan of the top emission type organic light emitting device.