Organic EL Element Host Compound Resistance Stability
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Solution Overview
Problem
Organic electroluminescent elements face challenges with significant resistance changes in the light emitting layer over time, affecting chromaticity and light emission properties, which impacts the durability and performance of organic electroluminescent devices.
Innovation Solution
Incorporating a compound with a specific structure featuring two or more aromatic heterocycles having 14 or more π electrons and a sterically bulky, electrically neutral portion to stabilize radical states and minimize charge transport property changes, thereby reducing film resistance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional host compounds are used in the light emitting layer, then the organic EL element can operate, but the film resistance changes significantly over time during current application
Solution Approach 1:
The patent changes the chemical structure parameters of the host compound by introducing a sterically bulky electrically neutral portion (such as adamantyl group) into the host molecule. This structural modification alters the physical and electrical properties of the light emitting layer, resulting in reduced resistance changes over time during operation.
Solution Approach 2:
The patent creates a composite host compound system by combining the original host compound (e.g., mCP) with a sterically bulky electrically neutral portion. This composite structure leverages the charge transport properties of the host compound while the bulky neutral portion provides structural stability and reduces molecular degradation, achieving both operational stability and resistance stability.
2Illumination intensity
If current is applied continuously to achieve luminescence, then light emission is maintained, but resistance change and voltage increase occur over time
Solution Approach 1:
The patent modifies the host compound structure to change the electrical and optical parameters of the light emitting layer. The introduction of the sterically bulky neutral portion stabilizes the molecular arrangement and charge transport pathways, maintaining consistent chromaticity and light emission properties even during continuous current application.
3Volume of moving object
If the light emitting layer is made thinner to reduce device size, then integration is improved, but resistance measurement and performance stability become more difficult
Solution Approach 1:
The patent changes the molecular parameters of the host compound to improve the electrical stability of thin films. The sterically bulky neutral portion prevents excessive molecular packing and degradation in thin layers, maintaining stable resistance and performance characteristics even when the light emitting layer thickness is reduced for device miniaturization.
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 results in an organic electroluminescent element with reduced resistance changes, improved chromatic purity, and stable light emission properties over time, enhancing the durability and performance of the device.
Implementation Method 1
Inclining a compound having a structure represented by Formula (1)... capable of stabilizing a radical state... two or more aromatic heterocycles having 14 or more π electrons and a sterically bulky, electrically neutral portion to stabilize radical states
Implementation Method 2
An organic electroluminescent element (hereafter, it is also called as an organic EL element) is a light emitting element having a constitution in which a light emitting layer containing a luminescent organic compound is interposed between a cathode and an anode. A hole injected from an anode and an electron injected from a cathode are recombined in the light emitting layer by applying an electric field, thus, an exciton is formed. It uses emitted light (fluorescence and phosphorescence) when the above exciton is deactivated.
Data Source
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AI summary
One objective of the present invention is to provide an organic EL element which is suppressed in change in the resistance of a light emitting layer after passing a current therethrough for a long period of time, thereby having good emission spectrum chromaticity, and which is suppressed in change in the emission characteristics over time. Another objective of the present invention is to provide a lighting device and a display device, each of which uses the organic EL element. An organic electroluminescent element of the present invention is provided with a pair of electrodes and one or more organic layers that are arranged between the pair of electrodes, and is characterized in that one or more layers among the organic layers contain a compound that has a structure represented by general formula (1).