Organic EL Display Panel with Segmented Charge Generating Layers
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Solution Overview
Problem
The challenge in organic electroluminescence (EL) display panels is the short lifespan of blue organic EL elements and the need for precise shadow masks to form charge generating layers, which increases manufacturing costs and reduces productivity, while the second blue light-emitting units in red and green sub-pixels only function for electron transport, leading to increased drive voltage.
Innovation Solution
An organic EL display panel design with a charge generating layer present in all sub-pixel regions, eliminating the need for precise shadow masks, and optimizing optical lengths to enhance light extraction efficiency and color purity, where the first and second blue light-emitting layers have specific emission peaks and optical lengths to efficiently extract blue light in the blue sub-pixel and suppress unwanted blue light in red and green sub-pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a precision shadow mask is used to form charge generating layers in only blue sub-pixel regions, then blue organic EL element longevity is improved, but manufacturing cost increases and productivity decreases
Solution Approach 1:
The display panel is divided into red, green, and blue sub-pixel regions with different charge generating layer configurations. Blue sub-pixels receive a charge generating layer to extend lifespan, while red and green sub-pixels omit this layer to avoid color contamination and maintain drive voltage efficiency
Solution Approach 2:
Different structural configurations are applied to different sub-pixel regions: blue sub-pixels have a charge generating layer for enhanced longevity, while red and green sub-pixels have a simplified structure without this layer to maintain their specific optical and electrical characteristics
2Duration of action of stationary object
If a precision shadow mask is used to form charge generating layers, then blue organic EL element longevity is improved, but manufacturing cost increases
Solution Approach 1:
The charge generating layer formation process is segmented by sub-pixel type, applying the layer only where needed (blue sub-pixels) rather than uniformly across all sub-pixels, thereby eliminating the need for complex precision shadow masks
Solution Approach 2:
The problem is solved by transitioning from a planar shadow mask approach to a multi-layer stacked structure where the charge generating layer is positioned between first and second light-emitting units, enabling selective formation through vertical stacking rather than lateral masking
3Illumination intensity
If the second blue light-emitting unit is formed only in blue sub-pixel regions, then blue light extraction efficiency is improved, but red and green sub-pixel drive voltage increases
Solution Approach 1:
The display panel is segmented into different sub-pixel types with optimized structures: blue sub-pixels contain second blue light-emitting units for enhanced light extraction, while red and green sub-pixels omit these units to maintain appropriate drive voltage levels
Solution Approach 2:
Different optical structures are applied locally to different sub-pixel regions based on their specific requirements: blue sub-pixels receive additional light-emitting units for maximum light extraction efficiency, while red and green sub-pixels maintain a simpler structure to avoid excessive drive voltage
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 design improves the longevity of blue organic EL elements, reduces manufacturing costs, and increases productivity by efficiently extracting light and maintaining color purity, while allowing for the formation of charge generating layers without precise shadow masks.
Implementation Method 1
An organic EL display panel includes a first blue light-emitting unit including a first blue light-emitting layer, a second blue light-emitting unit including a second blue light-emitting layer
Implementation Method 2
In the red sub-pixel region, an optical length between the light-emitting surface of the red light-emitting layer and the light-reflective surface of the first one of the light-reflective electrodes is from 20 nm to 50 nm
Data Source
AI summary
An organic EL display panel that includes light-reflective electrodes, a red light-emitting layer, a green light-emitting layer, a first blue light-emitting layer, a charge generating layer, a second blue light-emitting layer, and a light-transmissive electrode. In a red sub-pixel region, a first optical length is from 20 nm to 50 nm, and a second optical length is from 210 nm to 230 nm. In a green sub-pixel region, the first optical length is from 20 nm to 50 nm, and the second optical length is from 240 nm to 295 nm. In a blue sub-pixel region, the first optical length is from 20 nm to 60 nm, and the second optical length is from 195 nm to 205 nm.