Arylamine Capping Layer for OLED Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing organic electroluminescent devices face challenges in light extraction efficiency, particularly for blue light emission, due to materials with low refractive indices and poor thin film stability, which also affect color purity and durability.
Innovation Solution
An organic electroluminescent device is developed using a capping layer composed of an arylamine compound with a high refractive index, specifically an arylamine compound where two triphenylamine structures are joined within a molecule via a single bond or a divalent group without heteroatoms, enhancing light extraction efficiency and film stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a capping layer with low refractive index material is used, then the device structure is simple, but light extraction efficiency is poor
Solution Approach 1:
The patent changes the refractive index parameter of the capping layer material from conventional low values to high values (greater than 1.7), which fundamentally alters the optical properties at the interface between the capping layer and the light-emitting layer, thereby improving light extraction efficiency without complicating the device structure
Solution Approach 2:
The patent employs composite material design by combining the high refractive index capping layer material with the light-emitting layer and other device components, creating an optimized optical interface that enhances light extraction while maintaining structural integrity and simplicity
2Device complexity
If conventional capping layer materials are used, then the device structure is simple, but color purity deteriorates due to absorption
Solution Approach 1:
The patent selects capping layer materials with specific optical parameters (high refractive index and low absorption coefficient in the visible range), which simultaneously improve light extraction efficiency and maintain color purity by minimizing wavelength-dependent absorption
Solution Approach 2:
The patent uses organic compound materials for the capping layer that can be deposited as thin films, replacing more complex inorganic materials, thereby simplifying the device structure while achieving the desired optical performance for color purity
3Temperature
If inorganic substances with high vapor deposition temperatures are used for capping layer, then refractive index is high, but the light emitting device is damaged
Solution Approach 1:
The patent replaces inorganic materials requiring high-temperature vapor deposition with organic compound materials that can be deposited at lower temperatures, thereby avoiding thermal damage to the light-emitting device while achieving the required high refractive index for improved light extraction
Solution Approach 2:
The patent changes the material class from inorganic to organic compounds, which fundamentally alters the deposition temperature parameter from high (above 1000°C for inorganic materials like ZnSe) to lower temperatures suitable for the light-emitting device, while maintaining the high refractive index property
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 use of this arylamine compound in the capping layer significantly improves light extraction efficiency, maintains color purity, and extends the device's lifespan, making it suitable for full-color displays with clear, high-purity images.
Implementation Method 1
when light emitted in a light emitting layer is incident on the other film, if the light is incident at a certain angle or more, the light is totally reflected on an interface between the light emitting layer and the other film
Implementation Method 2
a light emitting device provided with a 'capping layer' with a high refractive index, on the outside of a semitransparent electrode with a low refractive index has been proposed to improve light extraction efficiency
Implementation Method 3
an organic EL device using a specific arylamine derivative... an organic EL device greatly improved in light extraction efficiency
Data Source
AI summary
An organic electroluminescent device having a capping layer composed of material having a high refractive index, excelling in thin film stability and durability and having no absorption in the respective wavelength ranges of blue, green, and red is provided to improve device characteristics of the organic electroluminescent device, particularly to greatly improve light extraction efficiency. The organic electroluminescent device has at least an anode electrode, a hole transport layer, a light emitting layer, an electron transport layer, a cathode electrode, and the capping layer in this order, wherein the capping layer contains an arylamine compound (X) having a structure in which two triphenylamine structures are joined within a molecule via a single bond or a divalent group that does not contain a heteroatom.