White Light Organic Electroluminescence Element with Multi-Layer Segmentation
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Solution Overview
Problem
White light-emitting organic electroluminescence elements using phosphorescent dopants in a single layer for illumination and display applications face challenges with stability of chromaticity, lifetime, and voltage requirements, as well as the generation of dark spots due to local light emission and energy transfer inefficiencies.
Innovation Solution
An organic electroluminescence element with a light-emitting layer having a contribution ratio of 0.3 to 1.0, incorporating a phosphorescent compound with specific ionization potential and UV degradation resistance, and including a hole-transporting and hole-injecting layer with matching ionization potentials, to enhance stability and reduce dark spots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent dopants are used in a single layer for white light emission, then light emission efficiency is improved, but chromaticity stability deteriorates
Solution Approach 1:
The patent divides the single light-emitting layer into multiple light-emitting layers, each containing a specific phosphorescent dopant with defined emission characteristics. This segmentation allows each layer to maintain stable chromaticity while collectively achieving high light emission efficiency through energy transfer between layers.
Solution Approach 2:
The patent transitions from a two-dimensional single-layer structure to a three-dimensional multi-layer structure with controlled energy transfer. By stacking multiple light-emitting layers with specific ionization potentials and emission wavelengths, the system achieves both high efficiency and chromaticity stability that cannot be obtained in a single layer.
2Ease of manufacture
If multiple light-emitting dopants with different emission wavelengths are used in a single element, then white light emission is achieved, but device complexity increases
Solution Approach 1:
The patent combines multiple light-emitting layers with different phosphorescent dopants into a unified organic electroluminescence element structure. The layers are integrated through controlled energy transfer mechanisms, allowing white light emission to be achieved while maintaining a relatively simple overall device structure compared to conventional approaches.
3Use of energy by moving object
If energy transfer from high emission energy dopant to low emission energy dopant is used, then light emission efficiency is improved, but dark spots are generated
Solution Approach 1:
The patent optimizes the local properties of each light-emitting layer by selecting specific phosphorescent dopants with appropriate emission wavelengths and ionization potentials. Each layer is designed with tailored energy levels to ensure uniform energy transfer throughout the structure, preventing localized energy accumulation that causes dark spots while maintaining high overall efficiency.
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 solution achieves a long lifetime, low voltage operation, and improved stability with reduced dark spots, ensuring excellent chromaticity and efficiency in white light emission for illumination and display devices.
Implementation Method 1
An organic electroluminescent element emits light through light emission (luminescence or phosphorescence) upon inactivation of excitons generated by recombining electrons and holes injected into the light-emitting layer
Implementation Method 2
a method for obtaining white light by mixing colors through using light-emitting pixels with different colors such as blue, green and red and making the light-emitting pixels simultaneously emit light
Data Source
AI summary
The purpose of the present invention is to provide: an organic electroluminescence element having a plurality of light-emitting dopants of different light-emitting wavelengths and emitting white light, the white-light-emitting organic electroluminescence element having excellent longevity, low-voltage driving, and chromatic stability, and also having a few dark spots; as well as an illumination device and a display device that use the element. This organic electroluminescence element contains at least one light-emitting layer sandwiched between a positive electrode and a negative electrode, the organic electroluminescence element characterized in that the light-emitting layer contribution ratio, defined as the ratio ΔPL/ΔEL of the photoluminescence intensity decay rate to the electroluminescence intensity decay rate, is 0.3 to 1.0.