Azomethine-Lithium Complex Electron Injection Layer for OLEDs
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Solution Overview
Problem
Current OLED technologies face challenges in achieving improved performance, particularly in electron injection, with existing materials like LiF requiring severe deposition conditions and having limitations in handling and deposition processes.
Innovation Solution
Development of novel compounds with specific structural formulas that can be used as electron injection layers, offering comparable or better performance to LiF without the need for severe deposition conditions, and can be deposited using various methods such as vacuum sublimation, organic vapor phase deposition, or solution processing, allowing for easier handling and lower temperature processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiF is used as electron injection layer, then electron injection performance is improved, but deposition conditions become severe and handling difficulty increases
Solution Approach 1:
The patent changes the chemical composition parameters from inorganic LiF to organic compounds (such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline and its derivatives), which fundamentally alters the deposition temperature range from high (severe) to low (mild conditions), while preserving the electron injection function
Solution Approach 2:
The patent employs organic compounds that can be deposited as thin films and serve as single-use electron injection layers, replacing the need for severe deposition conditions associated with inorganic materials like LiF, thereby simplifying the manufacturing process
2Reliability
If LiF is used as electron injection layer, then electron injection performance is improved, but handling difficulty increases
Solution Approach 1:
The patent transitions from inorganic LiF to organic compounds, changing the physical and chemical parameters such as volatility, solubility, and thermal stability, which enable easier handling through solution processing and vacuum deposition at low temperatures
Solution Approach 2:
The patent replaces the mechanical deposition process required for LiF with chemical vapor deposition or solution-based methods using organic compounds, eliminating the need for severe mechanical or thermal processing conditions
3Ease of manufacture
If conventional electron injection materials are used, then device fabrication is simpler, but voltage drift increases and device lifetime decreases
Solution Approach 1:
The patent employs composite structures where organic compounds are used in combination with dopants (such as alkali metals or alkaline earth metals) to create electron injection layers that maintain fabrication simplicity while achieving reduced voltage drift and enhanced device lifetime through optimized electronic properties
4Reliability
If LiF is used as electron injection layer, then electron injection performance is improved, but processing temperature must be high
Solution Approach 1:
The patent fundamentally changes the material composition from inorganic LiF to organic compounds, which shifts the deposition temperature parameter from high (above 600°C for LiF) to low (below 150°C for organic compounds), enabling electron injection performance without severe thermal conditions
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 novel compounds provide improved electron injection performance with reduced voltage drift and increased device lifetime compared to inorganic injectors, enabling more efficient and stable OLED device manufacturing.
Implementation Method 1
Embodiments of the compounds can be deposited by vacuum sublimation at temperatures significantly below that required for LiF (FIG. 13) e.g. below about 250° C.
Implementation Method 2
In addition to vacuum sublimation, embodiments of the compounds can be deposited by the organic vapour phase deposition (OVPD) process described inter alia by Universal Display Corporation in which organic films are deposited using an inert carrier gas to transfer films of organic material onto a cooled substrate
Data Source
AI summary
In OLEDs, improved efficiency is obtained by compounds which can form inter alia electron injection layers of the formula (I)whereinR1 is a 1-5 ring aryl (including polycyclic), aralkyl or heteroaryl group which is optionally substituted with one or more C1-C4 alkyl, alkoxy or cyano;R2 and R3 together form a 1-5 ring aryl (including polycyclic), aralkyl or heteroaryl group which is optionally substituted with C1-C4 alkyl, alkoxy or cyano;R4 is hydrogen, C1-C4 alkyl or aryl; andAr is monocyclic, bicyclic or tricyclic aryl or heteroaryl which is optionally substituted with one or more C1-C4-alkyl or alkoxy groups, or an oligomer thereof.