Top-Emitting Organic Device Light Scattering Layer
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Solution Overview
Problem
Existing organic light-emitting devices face challenges with photon trapping due to refractive index mismatch between materials, leading to low emission efficiency and durability issues from environmental factors like moisture and oxygen.
Innovation Solution
A top-emitting organic electronic device structure is developed with a light scattering layer between the base layer and electrode layer, which scatters and refracts light, enhancing emission efficiency and incorporating an encapsulation structure to prevent foreign substance ingress, using materials like titanium oxide and sol-gel coatings for the light scattering and planarization layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional transparent electrode layer with high refractive index (e.g., ITO with n≈2.0) is used, then the device structure is simple and easy to manufacture, but photons are trapped by total internal reflection at interfaces, resulting in low light extraction efficiency
Solution Approach 1:
A light scattering layer is introduced as an intermediary between the transparent electrode layer and the organic light-emitting layer. This scattering layer mediates the optical interaction by scattering photons that would otherwise be trapped by total internal reflection, thereby improving light extraction efficiency without requiring changes to the electrode materials themselves
Solution Approach 2:
The refractive index of the light scattering layer is specifically controlled to be between 1.3 and 1.6, which is lower than that of the transparent electrode layer (n≥2.0). This parameter change in refractive index creates favorable optical conditions for photon scattering and extraction, resolving the contradiction between manufacturing simplicity and light extraction efficiency
2Device complexity
If the organic layer and electrode layer are exposed to the environment, then the device structure is simple, but the organic materials are easily oxidized by moisture and oxygen, resulting in poor durability
Solution Approach 1:
An encapsulation structure consisting of multiple thin film layers is applied to cover and protect the organic layer and electrode layer. These thin film encapsulation layers act as barriers against moisture and oxygen penetration, significantly improving device durability without substantially increasing structural complexity
Solution Approach 2:
The encapsulation structure creates an inert protective environment around the sensitive organic materials, isolating them from harmful environmental factors such as moisture and oxygen. This inert barrier prevents oxidation and degradation reactions, thereby enhancing device reliability
3Device complexity
If no light scattering layer is used, then the device structure is simple, but photons are trapped by total internal reflection, resulting in low emission efficiency
Solution Approach 1:
The light scattering layer serves as an intermediary optical element that facilitates photon extraction. By introducing this dedicated scattering component, the device achieves high emission efficiency through enhanced light outcoupling without requiring complex multi-layer optical stacks or specialized electrode structures
Solution Approach 2:
The light scattering layer is formed as a composite structure containing scattering particles dispersed in a matrix material. This composite approach enables effective light scattering with relatively simple fabrication processes, improving emission efficiency without proportionally increasing device complexity
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 structure significantly improves light extraction efficiency and durability by preventing moisture and oxygen ingress, maintaining surface hardness and stability, as demonstrated by the organic light-emitting device's performance in Examples 1 and 2.
Implementation Method 1
a light scattering layer formed on the base layer
Implementation Method 2
scatters and refracts light, enhancing emission efficiency
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present application relates to a substrate for an organic electronic device, an organic electronic device, a method of preparing the substrate or the device, and a lighting apparatus. The substrate for an organic electronic device of the present application may, for example, be used to fabricate an organic electronic device, to which foreign substances such as moisture and oxygen are not permeated, and which has enhanced durability and superior light extraction efficiency. If the organic electronic device includes an encapsulation structure, the substrate may be stably attached to the encapsulation structure, and a surface hardness of outside connector part of the organic electronic device may be maintained to an appropriate level.