Organic EL Display Function Layer Thickness Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic light emitting elements with different emission colors face varying light extraction efficiency challenges due to differences in their organic light emitting layers, making it difficult to uniformly enhance light extraction across all elements in a coating type organic EL display.
Innovation Solution
Adjusting the thickness of the function layer formed by coating between the organic light emitting layer and the reflective electrode for each element, by varying the concentration of the functional material solution and the taper angle of the bank, to optimize the optical distance and light extraction efficiency for each color.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same bank height and taper angle are used for all color elements, then the manufacturing process is simple, but the film thickness uniformity varies per color
Solution Approach 1:
The patent applies different bank heights and taper angles for different color elements (R, G, B) according to their specific coating solution characteristics. This local differentiation ensures that each color element achieves optimal film thickness uniformity tailored to its material properties, resolving the contradiction between manufacturing simplicity and precision.
2Loss of energy
If the function layer thickness is increased to improve light extraction efficiency, then more light is extracted, but the optical distance becomes excessive causing attenuation
Solution Approach 1:
The patent optimizes the function layer thickness to specific ranges (50-200 nm for hole transport layer, 10-50 nm for electron transport layer) to achieve optimal light extraction efficiency. This parameter optimization ensures sufficient light extraction while preventing excessive optical distance that would cause light attenuation, resolving the contradiction between energy extraction and distance control.
3Manufacturing precision
If different bank configurations are used for each color element, then film thickness uniformity is improved, but the device complexity increases
Solution Approach 1:
The patent implements different bank configurations (heights and taper angles) specifically for different color elements based on their coating solution properties. This localized differentiation improves film thickness uniformity for each color while maintaining a relatively simple overall structure, as the complexity is confined to the bank configuration rather than the entire device architecture.
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 approach increases light extraction efficiency for all organic light emitting elements, resulting in a high-brightness and high-contrast organic EL display, while also allowing for larger display sizes and improved productivity through the coating method.
Implementation Method 1
Holes and electrons form electron-hole pairs in the organic light emitting layer, and function as luminescent exciters such that the organic light emitting layer emits light.
Implementation Method 2
the other one is used as a reflective electrode... the other part of lights go toward the reflective electrode and are reflected on the reflective electrode toward the transparent electrode.
Data Source
AI summary
Disclosed is a coated type organic EL display wherein the light extraction efficiencies of all organic light-emitting elements are improved even when the organic light-emitting elements have different organic light-emitting layers for respective emission colors. Specifically disclosed is an organic EL display which comprises a substrate, a red organic light-emitting element (R), a green organic light-emitting element (G), and a blue organic light-emitting element (B), said organic light-emitting elements being arranged on the substrate. Each of the organic light-emitting elements has a pixel electrode that is a reflective electrode, a functional layer that is formed on the pixel electrode by coating, an organic light-emitting layer that is arranged on the functional layer, a counter electrode that is a transparent electrode arranged on the organic light-emitting layer, and a tapered bank that defines the functional layer formed by coating. The amounts of the functional layers formed by coating are different among the element (R), the element (G) and the element (B), and the tapered angles of the banks defining the functional layers are different among the element (R), the element (G) and the element (B).