Electroluminescent Display Micro Lens Overcoat Light Extraction
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Solution Overview
Problem
The light extraction efficiency of electroluminescent display devices is degraded due to optical waveguide modes generated by surface plasmon components at the boundary between metal and the light-emitting layer, resulting in a significant portion of emitted light being trapped within the device rather than being outputted.
Innovation Solution
An electroluminescent display device is designed with an overcoat layer featuring micro lenses and a first electrode with varying thickness regions, where the light-emitting diode conforms to the micro lens morphology, enhancing light extraction by altering the optical path and reducing total reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional electroluminescent display device structure is used, then the device is simple to manufacture, but light extraction efficiency is degraded due to optical waveguide modes trapping 60-70% of emitted light
Solution Approach 1:
The overcoat layer is formed with a curved surface morphology featuring micro-lenses that have convex portions and concave portions. This curvature modifies the optical path of emitted light, reducing total internal reflection and enabling more light to escape the device. The micro-lens structure with varying surface curvature directly addresses the light trapping problem while maintaining manufacturing feasibility through standard deposition processes.
Solution Approach 2:
The first electrode is designed with non-uniform thickness, having a first thickness in a first region and a second thickness greater than the first thickness in a second region. This local variation in electrode thickness creates different optical properties in different regions, allowing optimized light extraction while controlling electrical resistance. The local quality principle enables simultaneous improvement of light extraction efficiency and electrical performance.
2Device complexity
If the first electrode has uniform thickness, then the manufacturing process is simpler, but light extraction efficiency remains degraded
Solution Approach 1:
The first electrode is designed with non-uniform thickness, having a first thickness in a first region and a second thickness greater than the first thickness in a second region. This local variation in electrode thickness creates different optical properties in different regions, allowing optimized light extraction while controlling electrical resistance. The local quality principle enables simultaneous improvement of light extraction efficiency and electrical performance.
Solution Approach 2:
The thickness parameter of the first electrode is varied across different regions to optimize both optical and electrical performance. By changing the thickness parameter locally rather than maintaining a uniform value, the design achieves improved light extraction efficiency while managing electrical resistance through the dual-region thickness configuration.
3Device complexity
If the overcoat layer has a flat surface, then the manufacturing process is simpler, but light extraction efficiency is degraded due to total internal reflection
Solution Approach 1:
The overcoat layer is formed with a curved surface morphology featuring micro-lenses that have convex portions and concave portions. This curvature modifies the optical path of emitted light, reducing total internal reflection and enabling more light to escape the device. The micro-lens structure with varying surface curvature directly addresses the light trapping problem while maintaining manufacturing feasibility through standard deposition processes.
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 configuration improves external quantum efficiency and current-luminance efficiency while maintaining reliability by preventing an increase in resistance, effectively extracting more light and enhancing display performance.
Implementation Method 1
an optical waveguide mode which is configured by a surface plasmon component generated at a boundary between a metal and the light-emitting layer 42 and the light-emitting layer 42 inserted between reflective layers at both sides accounts for about 60 to 70% of emitted light
Implementation Method 2
the overcoat layer includes a micro lens at a position corresponding to the emissive area, and the light-emitting diode conforms to a morphology of the micro lens
Implementation Method 3
an optical waveguide mode which is configured by a surface plasmon component generated at a boundary between a metal and the light-emitting layer 42
Data Source
AI summary
An electroluminescent display device comprises a substrate; a thin film transistor disposed on the substrate; an overcoat layer disposed on the thin film transistor; and a light-emitting diode electrically connected to the thin film transistor through the overcoat layer, wherein the light-emitting diode includes a first electrode, a light-emitting layer on the first electrode and a second electrode on the light-emitting layer, and an emissive area is an area in which the light-emitting layer emits light by the first electrode or the second electrode, wherein the overcoat layer includes a micro lens at a position corresponding to the emissive area, and the light-emitting diode conforms to a morphology of the micro lens, and wherein the first electrode includes a first region and a second region, the first region comprises an electrode layer, and the second region includes the electrode layer and an electrode pattern disposed under the electrode layer.