Benzazole Amine Capping Layer for Organic EL Light Extraction
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Solution Overview
Problem
Conventional organic electroluminescence (EL) devices face challenges in light extraction efficiency due to light absorption by materials, particularly in the 400 nm to 410 nm wavelength range, leading to reduced color purity and efficiency, especially when using capping layers with inorganic substances which are not suitable for high-temperature deposition and are affected by sunlight.
Innovation Solution
An organic EL device with a capping layer containing an amine compound having a benzazole ring structure, which has a high light absorption coefficient, refractive index, and excellent stability, allowing for deposition at temperatures below 400°C and maintaining color purity by absorbing light in the 400 nm to 410 nm range without affecting internal materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a capping layer with inorganic substances is used to improve light extraction efficiency, then light extraction efficiency is improved, but the device is affected by sunlight and cannot be deposited at high temperatures
Solution Approach 1:
The patent changes the material parameters of the capping layer from inorganic substances to organic compounds with specific molecular structures (formula 1). These organic compounds have deposition temperatures below 400°C and maintain stability under sunlight, resolving the contradiction between light extraction efficiency and environmental stability
Solution Approach 2:
The patent uses composite organic compounds containing specific functional groups (formula 1) that combine high light absorption coefficients in the blue region with appropriate refractive indices. This composite material approach achieves both improved light extraction efficiency and stability under operating conditions
2Area of stationary object
If light is extracted from the upper portion to widen the light emitting portion, then the light emitting area is widened, but light is totally reflected at interfaces reducing extraction efficiency
Solution Approach 1:
The patent optimizes the refractive index parameter of the capping layer organic compounds to match and enhance light extraction. By carefully selecting organic compounds with appropriate refractive indices (formula 1), the patent achieves high light extraction efficiency from the upper portion without total internal reflection losses
Solution Approach 2:
The capping layer acts as an optical intermediary between the light emitting layer and the external environment. The organic compounds in formula 1 serve as a mediator that facilitates light extraction by providing an optimal refractive index transition, enabling efficient light extraction across the widened emitting area
3Productivity
If materials with high light absorption coefficient are used in the capping layer, then light extraction efficiency is improved, but color purity is reduced due to absorption in visible ranges
Solution Approach 1:
The patent applies local quality by designing organic compounds (formula 1) with specific molecular structures that have high absorption coefficients only in the blue region (400-410 nm) while maintaining transparency in other visible ranges. This localized absorption property resolves the contradiction between light extraction efficiency and color purity
Solution Approach 2:
The patent changes the optical parameters of the capping layer materials by selecting organic compounds with tailored absorption spectra. The compounds in formula 1 have been designed to exhibit high absorption coefficients specifically in the blue region while maintaining appropriate refractive indices, achieving selective light extraction without compromising overall color purity
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 the benzazole ring structure in the capping layer significantly improves light extraction efficiency, maintains color purity, and extends the device's lifespan by effectively absorbing sunlight wavelengths that could otherwise impact the device's performance.
Implementation Method 1
the benzazole ring structure in the capping layer significantly improves light extraction efficiency, maintains color purity, and extends the device's lifespan by effectively absorbing sunlight wavelengths
Implementation Method 2
a light emitting device in which a 'capping layer' having a high refractive index is provided outside the translucent electrode having a low refractive index has been proposed
Data Source
AI summary
The present invention relates to an organic EL device having at least an anodic electrode, a hole transport layer, a light emitting layer, an electron transport layer, a cathodic electrode, and a capping layer in this order, in which the capping layer contains an amine compound having a benzazole ring structure represented by the following general formula (A-1).