Organic LED Light Scattering Layer with Tilted Side Surfaces
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Solution Overview
Problem
Conventional organic LED elements with resin-based light scattering layers face challenges in achieving even thickness and adhesiveness, leading to potential electrical deterioration and improper light-emitting action due to thermal contraction and difficulty in covering side surfaces with a thin film electrode.
Innovation Solution
An organic LED element with a glass-based light scattering layer having tilted side surfaces, allowing continuous coverage by a thin first electrode, and incorporating barrier layers to prevent alkali metal ion migration, enhancing light extraction efficiency and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resin-based light scattering layer is used, then light extraction efficiency is enhanced, but it becomes extremely difficult to place another layer continuously with even thickness on the upper surface or side surfaces
Solution Approach 1:
The patent applies preliminary action by forming a planarization layer before depositing the transparent electrode. This planarization layer fills in the irregularities and perpendicular side surfaces of the resin-based light scattering layer, creating a flat surface that enables subsequent layers to be deposited with uniform thickness and continuous coverage.
Solution Approach 2:
The patent introduces a planarization layer as an intermediary between the resin-based light scattering layer and the transparent electrode. This intermediate layer mediates the incompatibility between the perpendicular side surfaces of the scattering layer and the requirement for continuous even-thickness electrode deposition.
2Reliability
If a light scattering layer with perpendicular side surfaces is used, then light scattering function is achieved, but the stepped part height difference increases making it extremely difficult to form continuous layers
Solution Approach 1:
The planarization layer is formed in advance to compensate for the height difference created by the light scattering layer's perpendicular side surfaces. This preliminary action reduces the stepped part height difference, enabling subsequent layers to be formed continuously without interruption.
3Reliability
If a resin-based light scattering layer is used, then light extraction is improved, but thermal contraction occurs causing exfoliation and cracks in the electrode
Solution Approach 1:
The planarization layer serves as a buffer between the resin-based light scattering layer and the transparent electrode. During thermal contraction, this intermediate layer absorbs dimensional changes and stress, preventing direct transmission of contraction forces to the electrode, thereby avoiding exfoliation and crack formation.
Solution Approach 2:
The planarization layer provides beforehand cushioning by being positioned between the thermally contracting resin layer and the electrode. It anticipates and absorbs the thermal contraction effects before they can damage the electrode structure.
4Reliability
If the light scattering layer thickness is increased to improve light extraction, then more scattering materials are available, but the stepped part height difference becomes even larger
Solution Approach 1:
The planarization layer is formed as a preliminary step to fill the increased height difference that results from using a thicker light scattering layer. This allows the system to benefit from enhanced light extraction through increased scattering material while maintaining manufacturable layer thickness uniformity.
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 increases light emission area, prevents electrode deterioration, and maintains stable light-emitting characteristics over time by using a glass-based light scattering layer with tilted side surfaces and barrier layers to address the issues of evenness and thermal contraction.
Implementation Method 1
since a part of emitted light generated in the organic layer is scattered by the scattering materials in the light scattering layer
Data Source
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AI summary
The present invention provides an organic LED element having the significantly larger light emission area than conventional ones. The invention relates to an organic LED element, comprising: a transparent substrate; a light scattering layer formed on the transparent substrate; a transparent first electrode formed on the light scattering layer; an organic light-emitting layer formed on the first electrode; and a second electrode formed on the organic light-emitting layer, wherein the light scattering layer has a base material comprising a glass, and a plurality of scattering materials dispersed in the base material; the light scattering layer has a bottom surface on the transparent substrate side, an upper surface on the first electrode side and side surfaces, and each of the side surfaces of the light scattering layer has a surface tilted at an angle larger than right angle from the upper surface toward the bottom surface; and the first electrode is placed so as to continuously cover the side surfaces of the light scattering layer.