Organic Electroluminescence Device Refractive Index Optimization
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Solution Overview
Problem
Organic electroluminescence devices face challenges in achieving high light extraction efficiency due to significant loss components when using metal electrodes, which lead to increased driving voltage and decreased electrical power efficiency, and the use of thicker electron transport layers to mitigate these issues complicates manufacturing and increases costs.
Innovation Solution
The implementation of a second organic layer with a refractive index lower than the first organic layer in the thickness direction reduces non-propagating light loss without increasing the thickness of the electron transport layer, thereby enhancing light extraction efficiency and maintaining productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a metal electrode is used, then electrical conductivity is improved, but light extraction efficiency deteriorates due to significant loss components
Solution Approach 1:
An organic layer is introduced as an intermediary between the metal electrode and the light-emitting layer. This intermediate layer mediates the interaction between light and the metal electrode, reducing the loss component and improving light extraction efficiency while maintaining the electrical conductivity benefits of the metal electrode.
2Loss of energy
If the electron transport layer thickness is increased, then light extraction efficiency is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of increasing the thickness of the electron transport layer, the invention changes the refractive index parameter of the organic layer. By selecting an organic layer with a refractive index lower than that of the light-emitting layer, the patent achieves improved light extraction efficiency without increasing layer thickness or manufacturing complexity.
3Loss of energy
If the electron transport layer thickness is increased, then light extraction efficiency is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the refractive index parameter of the organic layer rather than increasing thickness. This approach maintains simple manufacturing processes and low costs while achieving improved light extraction efficiency through optical parameter optimization.
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 increases the external and substrate mode light extraction components while minimizing the loss component, resulting in improved light extraction efficiency without the drawbacks of increased voltage drop and material usage, thus achieving a balance between performance and manufacturing feasibility.
Implementation Method 1
A refractive index of the second organic layer in a thickness direction for the light is lower than a refractive index of the first organic layer for the light
Data Source
AI summary
According to one embodiment, an organic electroluminescence device includes a first electrode, a second electrode, a first organic layer and a second organic layer. The second electrode includes a metal. The first organic layer is provided between the first electrode and the second electrode. The first organic layer is configured to emit light. The second organic layer is provided between the first organic layer and the second electrode. A refractive index of the second organic layer in a thickness direction for the light is lower than a refractive index of the first organic layer for the light.