Ionic Polymer Charge Generation Layer for Atmospheric Organic EL Stability
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Solution Overview
Problem
Conventional organic electroluminescent elements (EL) with charge generation layers using alkali metals or alkali metal fluorides degrade quickly due to moisture and oxygen exposure, leading to reduced brightness and shortened lifespan, especially when formed in non-vacuum atmospheric conditions.
Innovation Solution
Employing an ionic polymer with specific structural units in the charge generation layer that maintains charge generation characteristics even at normal atmospheric pressure, allowing for the formation of multi-photon-type organic EL elements with improved stability and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alkali metals or alkali metal fluorides are used in the charge generation layer, then charge generation characteristics are improved, but the element degrades quickly due to moisture and oxygen exposure
Solution Approach 1:
The patent changes the chemical composition parameters of the charge generation layer from conventional alkali metals/fluorides to ionic polymers with specific chemical structures (containing quaternary ammonium salts, phosphonium salts, or sulfonium salts). This parameter change maintains charge generation capability while dramatically improving resistance to moisture and oxygen, thereby extending element lifespan.
2Reliability
If the charge generation layer is formed in vacuum atmosphere, then oxidation is prevented, but manufacturing complexity and cost increase
Solution Approach 1:
The patent employs ionic polymers that are inherently stable in atmospheric conditions, eliminating the need for expensive vacuum atmosphere control during manufacturing. The material itself acts as its own protective mechanism, allowing formation in normal atmospheric conditions and simplifying the manufacturing process.
3Ease of manufacture
If the light-emitting layer is formed by coating method in normal atmospheric pressure, then manufacturing is simplified, but the charge generation layer degrades due to moisture and oxygen
Solution Approach 1:
The patent uses ionic polymers as composite materials for the charge generation layer that combine charge generation functionality with inherent atmospheric stability. These composite materials can be processed by coating methods in normal atmospheric pressure without degradation, enabling both manufacturing simplicity and layer stability.
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 ionic polymers in the charge generation layer enhances the stability and performance of organic EL elements, enabling their manufacture in normal atmospheric conditions without compromising brightness or lifespan, thus simplifying the manufacturing process and reducing costs.
Implementation Method 1
the charge generation layer is a layer generating a hole and an electron by applying an electric field
Implementation Method 2
the injected hole and the injected electron are coupled with each other in the light-emitting layer to generate light emission
Data Source
Figure 1
AI summary
The present invention provides a multi-photon-type organic electroluminescent element including a charge generation layer using a material that is difficult to be degraded even at around normal atmospheric pressure. In an organic electroluminescent element (10) including a pair of electrodes consisting of an anode (32) and a cathode (34), a plurality of light-emitting layers (50) provided between the electrodes, and a charge generation layer (70) provided between the light-emitting layers adjacent to each other, the charge generation layer contains an ionic polymer generating at least any one of an electron and a hole.