Organic Capping Layer Compound for Light Extraction Efficiency
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Solution Overview
Problem
Current organic electroluminescent elements with top emission structures face limitations in light extraction efficiency due to the use of inorganic capping layers, which are prone to deformation at high temperatures and result in poor color purity and efficiency, especially when using materials like ZnSe or Alq3.
Innovation Solution
A compound with a high refractive index and low extinction coefficient, suitable for a capping layer, is designed to improve light extraction efficiency by modifying the molecular structure with a benzene skeleton, providing stability and durability as a thin film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If inorganic capping layers (e.g., ZnSe) are used in top emission organic EL elements, then light extraction efficiency is improved, but the elements suffer from poor color purity and reduced lifespan due to material instability and deformation at high temperatures
Solution Approach 1:
The patent changes the material parameter from inorganic (ZnSe) to organic compound (formula 1), which fundamentally alters the thermal stability, color purity, and lifespan characteristics while maintaining the high refractive index property needed for light extraction efficiency
Solution Approach 2:
The patent uses an organic compound with a specific molecular structure (formula 1) that combines high refractive index properties with thermal stability, creating a composite material that resolves the contradiction between light extraction efficiency and reliability
2Loss of energy
If inorganic capping layers are used, then light extraction efficiency is improved, but manufacturing precision deteriorates due to mask deformation at high temperatures
Solution Approach 1:
The patent changes the material from inorganic to organic compound, which has lower processing temperature requirements and better mask stability, thereby improving manufacturing precision while maintaining light extraction efficiency through the high refractive index property
3Ease of manufacture
If Alq3 is used as capping layer material, then ease of manufacture is improved, but light extraction efficiency and color purity deteriorate due to absorption at 450 nm
Solution Approach 1:
The patent modifies the molecular structure by changing the core aromatic group and substituent patterns in the organic compound formula (1), which shifts the absorption spectrum away from 450 nm while maintaining vapor-depositability and ease of manufacture
Solution Approach 2:
The patent specifically designs the molecular structure with particular aromatic groups and substituent patterns that provide low absorption at blue wavelengths (450 nm) while maintaining other desirable properties like ease of deposition and high refractive index
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 compound significantly enhances light extraction efficiency, maintains color purity, and extends the lifespan of organic electroluminescent elements by offering a stable and efficient capping layer solution.
Implementation Method 1
A compound with a high refractive index and low extinction coefficient, suitable for a capping layer, is designed to improve light extraction efficiency
Implementation Method 2
low extinction coefficient
Data Source
AI summary
It is an object of the present invention to provide a compound for a capping layer that has a high refractive index and a low extinction coefficient in a range of 450 nm to 750 nm to improve the light extraction efficiency of an organic EL element. The present invention has focused on the fact that compounds having a benzene skeleton at the center thereof are excellent in stability and also durability in the form of a thin film, and that the refractive index thereof can be improved by modifying the molecular structure, and thus, molecules have been designed. Provided is a compound represented by a general formula (1), and an organic EL element with excellent luminance efficiency is obtained by using that compound as a constituent material of a capping layer.