Top Emitting OLED Coupling-Out Layer Frequency Conversion
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Solution Overview
Problem
Top emitting electroluminescent components face low light coupling-out efficiency due to total reflections at interfaces, with only about 20% of generated luminescence being perceived as external optical modes, limiting their energy efficiency and performance.
Innovation Solution
Incorporating a coupling-out layer with frequency conversion centers on the side of the second electrode remote from the organic layer, which absorbs and re-emits light with an altered frequency, reducing total reflection and enhancing light coupling-out efficiency by over 100%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a top emitting electroluminescent component uses conventional transparent electrodes and organic layers with different refractive indices, then the component structure is simple and easy to manufacture, but total reflections at interfaces cause low light coupling-out efficiency with only about 20% of generated luminescence being perceived as external optical modes
Solution Approach 1:
The patent introduces a coupling-out layer as an intermediary component between the organic light-emitting layer and the external environment. This layer contains frequency conversion centers that mediate the interaction between trapped optical modes and external space, enabling efficient light extraction without complicating the basic OLED structure. The coupling-out layer acts as a bridge that converts internally trapped light into extractable external modes.
Solution Approach 2:
The patent changes the optical parameters of the system by introducing frequency conversion centers in the coupling-out layer. These centers absorb light at one frequency and re-emit it at a different frequency, thereby changing the optical characteristics of the light as it passes through the component. This parameter change enables the light to escape from total reflection constraints and be efficiently coupled out.
2Illumination intensity
If the component structure includes multiple layers with different refractive indices (substrate, electrodes, organic layers), then the component can achieve desired optical properties, but optical modes are trapped within layers and interfaces causing energy loss
Solution Approach 1:
The patent converts the harmful effect of total reflection and trapped optical modes into a beneficial process. By introducing frequency conversion centers in the coupling-out layer, the trapped light that would normally be lost is instead absorbed and re-emitted at a different frequency, enabling it to escape as external optical modes. This transforms the energy loss from total reflection into useful light extraction.
3Device complexity
If no coupling-out layer is used, then the component structure remains simple, but the proportion of light that can leave the component is limited to approximately 20% of total luminescence
Solution Approach 1:
The patent segments the optical extraction function from the basic electroluminescent structure by adding a separate coupling-out layer. This segmentation allows the light extraction function to be optimized independently through frequency conversion centers, while the core OLED structure remains simple and unchanged. The coupling-out layer handles the complex light management task without complicating the manufacturing of the main component.
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 coupling-out layer increases light extraction efficiency significantly, allowing a greater proportion of light to be emitted, improving the overall performance of top emitting electroluminescent components, including displays and illumination elements.
Implementation Method 1
said coupling-out layer comprising frequency conversion centres which partly absorb the light emitted in the at least one organic layer and emit it again with an altered frequency
Implementation Method 2
frequency conversion centres which partly absorb the light emitted in the at least one organic layer
Data Source
AI summary
In order, in the case of an OLED, to improve the coupling-out efficiency, a top emitting electroluminescent component (100) is proposed, comprising a substrate (110), a first electrode (120) closest to the substrate, a transparent electrode (140) located at a distance from the substrate, and at least one light-emitting organic layer (130) arranged between the two electrodes. The component according to the invention is distinguished by the fact that a coupling-out layer (150) is arranged on that side of the second electrode which is remote from the at least one organic layer, said coupling-out layer comprising conversion centres (151) which partly absorb the light emitted by the at least one organic layer and emit it again with an altered frequency. In this way, directional light penetrating into the coupling-out layer is emitted again in non-directional fashion, so that a part of the light which would be captured by means of total reflection without the influence of the frequency conversion centres within the coupling-out layer can indeed leave the coupling-out layer.