High-Refractive-Index Capping Layer for OLED Light Extraction
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Solution Overview
Problem
Current organic electroluminescent devices (OLEDs) suffer from low external quantum efficiency due to light being confined within the device, with existing capping layer materials having low refractive indices and inadequate light extraction efficiency across all colors, leading to color shift issues at multi-angle displays.
Innovation Solution
A compound with a specific molecular structure is introduced, featuring a high refractive index and minimal color shift across different wavelengths, which is used as a capping layer to enhance light extraction and luminous efficiency, particularly improving external quantum efficiency and reducing color shift in OLEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If existing capping layer materials are used, then the device structure is simple, but the light extraction efficiency is low and external quantum efficiency is poor
Solution Approach 1:
The patent changes the refractive index parameter of the capping layer material from conventional low values to a high refractive index value of 2.0 or higher. This parameter change enables more effective light extraction by better impedance matching with the surrounding media, resolving the contradiction between material simplicity and light extraction efficiency.
Solution Approach 2:
The patent employs composite material strategies by combining the high refractive index compound with specific organic luminescent layers and electrode structures. This composite approach optimizes both the optical extraction performance and the structural simplicity, achieving high external quantum efficiency while maintaining ease of manufacture.
2Device complexity
If conventional capping layer materials are used, then the manufacturing process is simple, but color shift occurs at multi-angle displays
Solution Approach 1:
The patent changes the optical parameters of the capping layer by using a compound with high refractive index and specific optical properties that minimize angle-dependent color shift. This parameter optimization allows the simple capping layer structure to maintain excellent color consistency across wide viewing angles.
3Loss of energy
If the refractive index of capping layer is increased, then light extraction efficiency is improved, but material selection becomes more limited
Solution Approach 1:
The patent develops composite material systems where the high refractive index compound is integrated with various organic luminescent layers (blue, green, red emitting layers). The compound's chemical structure is designed to be compatible with multiple organic materials, ensuring excellent interfacial properties and charge transport while maintaining high refractive index for superior light extraction.
Solution Approach 2:
The high refractive index compound serves multiple functions simultaneously: it acts as the capping layer for light extraction, provides charge transport pathways, ensures chemical compatibility with different luminescent materials, and maintains structural stability. This multi-functionality resolves the contradiction between improved light extraction and material versatility.
4Device complexity
If existing materials are used, then the device structure is straightforward, but external quantum efficiency remains low at 20%
Solution Approach 1:
The patent changes the key optical parameter of the capping layer by introducing a compound with refractive index of 2.0 or higher. This single parameter change in the capping layer structure enables external quantum efficiency to exceed 30%, more than doubling the light extraction performance while maintaining the straightforward device structure without complex modifications.
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 improves light extraction and luminous efficiency, reduces color shift at multi-angle displays, and provides high thermal stability and durability, extending the device's lifespan by blocking harmful UV light.
Implementation Method 1
the compound provided in the present application has a high refractive index in the visible light region, thereby helping to improve the light extraction efficiency and luminous efficiency
Implementation Method 2
The compound provided in the present application almost does not have absorbance in the respective wavelength regions of blue, green and red light, so that the color purity does not decrease
Data Source
AI summary
The present application discloses a compound, a display panel and a display device. The compound has the structure shown in Formula 1. The compound of the present application can improve the light extraction efficiency and luminous efficiency, especially the external quantum efficiency of a device, and can also effectively reduce the color shift of the device at multi-angle display.