Low-Refractive Members for Electroluminescent Display Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electroluminescent display devices suffer from low light extraction efficiency due to optical waveguide modes generated at the boundary between metal and the emitting layer, resulting in a significant portion of emitted light being trapped within the device.
Innovation Solution
Incorporating low-refractive members with specific geometrical features, such as inclined surfaces, below a first electrode and forming a light extraction member on its inclined surface, to enhance light extraction efficiency by altering the optical path of trapped light.
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 patent introduces low-refractive members with specific refractive index values (lower than surrounding layers) to change the optical parameters of the device. This refractive index contrast modifies the optical path and reduces waveguide mode formation, enabling trapped light to escape while maintaining a relatively simple manufacturing process using existing semiconductor fabrication techniques
Solution Approach 2:
The low-refractive members act as intermediary structures between the emitting layer and the substrate/encapsulation layers. These intermediate elements with lower refractive index serve as optical mediators that redirect trapped light paths, allowing light to escape from regions where it would otherwise be confined by total internal reflection at high-refractive-index interfaces
2Loss of energy
If low-refractive members with inclined surfaces are introduced, then light extraction efficiency is improved by redirecting trapped light, but device complexity increases
Solution Approach 1:
Rather than modifying the entire device structure, the patent segments the solution into discrete low-refractive members positioned at specific locations (below the first electrode and at interfaces where waveguide modes form). This segmentation allows light extraction enhancement without requiring complex modifications to the entire device architecture
Solution Approach 2:
The patent addresses the two-dimensional plane of light propagation by introducing vertical dimensionality through low-refractive members with inclined surfaces. The inclined surfaces create three-dimensional optical paths that redirect trapped light in multiple directions, breaking the planar waveguide mode confinement without requiring complex lateral structures
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 described configuration effectively increases the amount of emitted light by redirecting trapped light to exit the device, thereby improving light extraction efficiency.
Implementation Method 1
a refractive index of each of the plurality of low-refractive members is lower than those of the overcoat layer and the first electrode
Data Source
AI summary
An electroluminescent display device includes an overcoat layer on a substrate; a plurality of low-refractive members formed of an inorganic matter and disposed on the overcoat layer; a first electrode on the overcoat layer and the plurality of low-refractive members; a bank layer disposed on the overcoat layer and the first electrode and including an opening configured to expose the first electrode; an emitting layer disposed on the first electrode; and a second electrode disposed on the emitting layer, wherein each of the plurality of low-refractive members includes a first flat surface contacting the first electrode, a second flat surface having an area greater than that of the first flat surface and contacting the overcoat layer and first and second inclined surfaces connecting the first flat surface and the second flat surface, and, wherein a refractive index of each of the plurality of low-refractive members is lower than those of the overcoat layer and the first electrode.