Organic Light Emitting Display Device with Interlayer Charge Transport
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Solution Overview
Problem
Existing organic light emitting display devices face issues with interfacial properties and luminous efficiency due to the use of inorganic charge transport layers, which can lead to unstable manufacturing processes and decreased device lifespan, especially when using water-soluble hole transport layers and hydrophobic emission layers.
Innovation Solution
An organic light emitting display device with multiple emission layers and an organic charge transport layer having a stacked structure of tris-(8-hydroxyquinoline)-aluminum (Alq3), copper phthalocyanine (CuPC), and N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB), enhancing interfacial properties and luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inorganic charge transport layer is used, then electron and hole transport capability is improved, but interfacial properties with organic emission layers deteriorate and manufacturing stability decreases
Solution Approach 1:
The patent applies homogeneity by using organic materials for both the emission layers and charge transport layers, ensuring compatible chemical properties and interfacial characteristics throughout the device structure, which resolves the interfacial incompatibility between inorganic and organic materials
Solution Approach 2:
The patent changes the material composition parameter from inorganic to organic for the charge transport layers, fundamentally altering the chemical nature of the interface to achieve better compatibility with organic emission layers while maintaining charge transport functionality
2Ease of manufacture
If water-soluble hole transport materials are used, then ease of manufacture is improved, but interfacial properties with hydrophobic emission layers deteriorate
Solution Approach 1:
The patent uses polymer-based hole transport materials that are chemically compatible with the polymer emission layers, ensuring homogeneous interfacial properties throughout the device while maintaining ease of manufacturing through solution processing
Solution Approach 2:
The patent employs composite polymer structures where the hole transport layer and emission layer are both polymer-based, creating a chemically compatible composite system that maintains good interfacial properties while allowing solution-based manufacturing
3Loss of energy
If multiple emission layers are stacked, then luminous efficiency is improved, but device complexity increases
Solution Approach 1:
The patent uses a universal polymer-based charge transport layer design that can be applied between multiple different emission layers, allowing the same material system to serve multiple functions and reducing the complexity that would arise from using different materials for each interface
Solution Approach 2:
The patent changes the structural parameter by using repeated units of emission layer-charge transport layer throughout the device, creating a modular structure that achieves high luminous efficiency through multiple interfaces while maintaining manufacturing simplicity through parameter repetition
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 an organic charge transport layer with specific mobility ratios and materials improves luminous efficiency and interfacial properties, increasing the lifespan and performance of the device while allowing for easier manufacturing processes.
Implementation Method 1
an electron mobility and a hole mobility which are different by a factor of 100 or less
Implementation Method 2
the hole and the electron are recombined in the emission layer, thereby creating an exciton. Thus, light is emitted while the exciton is transitioned from an excited state to a ground state
Data Source
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AI summary
An organic light emitting display device having multiple emission layers (230,232) is provided, in which an organic charge transport layer (240) is interposed between the emission layers (230,232) to enhance interfacial properties between layers, and thus a stable process is ensured. Further, a hole transport layer and an electron transport layer are formed of an organic material like the charge transport layer, thereby simplifying the process.