OLED Electron Injection Layer Using Metal-Free Organic Phosphines
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Solution Overview
Problem
Existing electron injection layers in OLEDs use toxic and mutagenic compounds like LiF and LiQ, posing health risks and requiring complex deposition processes, and they also result in high operating voltages and inefficient electron injection.
Innovation Solution
Employing an electron injection layer composed of organic phosphine compounds, free of metals, metal salts, and metal complexes, which are thermally stable and facilitate direct contact with a cathode electrode containing zero-valent metals, allowing for low operating voltages and high external quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium halides and lithium organic complexes are used to enhance electron injection, then electron injection efficiency is improved, but health and safety risks increase due to toxicity and mutagenicity
Solution Approach 1:
The patent extracts and eliminates lithium compounds from the electron injection layer, replacing them with organic phosphine compounds. This removes the harmful lithium-containing substances while maintaining the electron injection function through alternative organic materials that form dipole moments at the cathode interface.
Solution Approach 2:
The patent employs organic phosphine compounds that can be deposited as thin films and serve their function without requiring the persistence or accumulation of harmful lithium compounds. These organic compounds provide the necessary electron injection enhancement temporarily during device operation without long-term health risks.
2Reliability
If metal salts and metal complexes are used in electron injection layers, then electron injection is enhanced, but deposition process complexity and time increase
Solution Approach 1:
The patent removes metal salts and metal complexes from the electron injection layer composition, using only organic phosphine compounds. This simplifies the deposition process by eliminating the need for complex co-deposition techniques and multiple material handling procedures associated with metal-containing compounds.
Solution Approach 2:
The patent changes the chemical composition parameters of the electron injection layer from metal-containing compounds to purely organic phosphine compounds. This parameter change simplifies the deposition process while maintaining the functional performance of electron injection enhancement through dipole moment formation.
3Reliability
If conventional electron injection layers are used, then electron injection function is provided, but operating voltage remains high
Solution Approach 1:
The patent changes the chemical composition of the electron injection layer to organic phosphine compounds with specific molecular structures that generate favorable dipole moments. This parameter change in material composition directly reduces the energy barrier for electron injection, thereby lowering the operating voltage of the OLED device.
Solution Approach 2:
The patent uses organic phosphine compounds that combine specific functional groups and molecular structures to create a composite material system at the cathode interface. This composite structure provides both the electron injection enhancement and the voltage reduction through optimized dipole moment formation and interface properties.
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 organic phosphine compounds enable rapid deposition, reduce health risks, lower operating voltages, and enhance efficiency, resulting in improved OLED performance and manufacturing yield.
Implementation Method 1
the organic phosphine compound or a combination of two or more thereof forms a dipole moment at an interface with the cathode electrode
Implementation Method 2
electrons injected from the cathode electrode move to the EML, via the ETL
Data Source
AI summary
The invention relates to Organic light emitting diode comprising at least one emission layer, an electron injection layer and at least one cathode electrode, wherein:the electron injection layer comprises an organic phosphine compound, wherein the electron injection layer is free of a metal, metal salt, metal complex and metal organic compound;the cathode electrode comprises at least a first cathode electrode layer, whereinthe first cathode electrode layer comprises a first zero-valent metal selected from the group comprising alkali metal, alkaline earth metal, rare earth metal and/or a group 3 transition metal; andthe electron injection layer is arranged in direct contact to the first cathode electrode layer.