Organic Electroluminescence Element Light-Outcoupling Structure
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Solution Overview
Problem
Existing organic electroluminescence elements face challenges in achieving high light-outcoupling efficiency due to total reflection losses at the interface between the organic layer and the substrate, leading to low color stability and increased view angle dependency, particularly in white emission applications.
Innovation Solution
An organic electroluminescence element with a light-outcoupling structure featuring an uneven surface on the substrate, comprising a matrix of protruded and recessed sections with a refractive index similar to or lower than the substrate, and a transparent cover layer, which reduces total reflection and enhances light emission while minimizing color difference across viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat interface between the organic layer and substrate is used, then the device structure is simple, but total reflection loss occurs and light-outcoupling efficiency is low
Solution Approach 1:
The patent applies curvature by forming an uneven surface structure with protrusions and recesses on the substrate interface instead of a flat surface. This curved/uneven geometry modifies light propagation paths at the interface, reducing total reflection loss and improving light-outcoupling efficiency while maintaining manufacturing feasibility through established patterning techniques.
2Ease of manufacture
If a conventional interface structure is used, then manufacturing is easy, but color stability is poor and view angle dependency increases
Solution Approach 1:
The uneven surface structure with controlled protrusions and recesses creates multiple light extraction paths that reduce interference effects and improve color stability. The curved geometry distributes light emission more uniformly across different viewing angles, reducing view angle dependency while maintaining manufacturing simplicity through standard fabrication 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
The solution significantly improves light-outcoupling efficiency and reduces color variation with viewing angle, resulting in enhanced light emission performance and stability for organic electroluminescence elements.
Implementation Method 1
total reflection losses at the interface between the organic layer and the substrate
Implementation Method 2
made of material having a refractive index almost equal to a refractive index of the moisture-proof substrate or lower than the refractive index of the moisture-proof substrate
Data Source
AI summary
The organic electroluminescence element includes: a moisture-proof substrate; a light emitting stack including a first electrode, a light emitting layer, and a second electrode; and an enclosing member bonded to the substrate to enclose the stack. The element further includes a light-outcoupling structure provided on a side of the substrate facing the first electrode and having an uneven structure made of material having a refractive index almost equal to or lower than a refractive index of the substrate. The uneven structure includes a plane divided into a matrix of sections, and multiple protruded parts having almost same heights individually allocated to desired sections of the matrix. With regard to an arbitrary region of the plane, a ratio of a total area of one or some of the multiple protruded parts in the arbitrary region to an area of the arbitrary region is almost constant.