Organic Electroluminescence Device with Carbazolyl Hole Transport Layer
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Solution Overview
Problem
Conventional organic electroluminescence devices have insufficient luminous efficiency and are sensitive to the thickness of the electron transporting layer, leading to instability and reduced durability due to the use of materials that produce unstable oxidized species with carbazolyl groups.
Innovation Solution
An organic electroluminescence device is designed with a light emitting layer containing a phosphorescent metal complex having a monoanionic bidentate ligand and a compound with a carbazolyl group, which reduces the dependence on electron transporting layer thickness and enhances luminous efficiency by controlling carrier balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional electron transporting materials with carbazolyl groups are used, then device fabrication is simplified, but device lifespan is shortened due to unstable oxidized species
Solution Approach 1:
The patent extracts the carbazolyl group from the electron transporting material and relocates it to the hole transporting layer. This separation removes the harmful oxidized species generation from the electron transporting layer, thereby extending device lifespan while maintaining ease of manufacture through the use of familiar carbazole-based materials in the hole transporting layer.
Solution Approach 2:
The patent introduces a hole transporting layer as an intermediary between the anode and the electron transporting layer. This intermediary layer absorbs the oxidative stress and stabilizes the system, preventing the formation of unstable oxidized species in the electron transporting layer while maintaining overall device functionality.
2Device complexity
If conventional materials are used in the electron transporting layer, then device structure is simplified, but luminous efficiency is insufficient and depends on layer thickness
Solution Approach 1:
The patent segments the device into distinct functional layers with specialized materials: a hole transporting layer containing carbazolyl groups for stability, and an electron transporting layer optimized for electron injection and transport. This segmentation allows each layer to be optimized for its specific function, improving overall luminous efficiency while maintaining clear structural organization.
Solution Approach 2:
The patent employs composite material strategies by combining different material classes in separate layers: carbazole-based compounds in the hole transporting layer and electron transporting materials in the electron transporting layer. This composite approach leverages the advantages of each material type to achieve high luminous efficiency and reduced thickness dependence.
3Adaptability or versatility
If electron transporting layer thickness is varied, then device manufacturing flexibility is improved, but luminous efficiency becomes unstable
Solution Approach 1:
The patent performs preliminary optimization of the electron transporting layer by placing it in direct contact with the light-emitting layer and optimizing its thickness and material composition beforehand. This preliminary action ensures that the electron transporting layer maintains stable electron injection and transport performance across a range of thicknesses, making the device less sensitive to manufacturing variations.
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 device achieves improved luminous efficiency and stability by preventing excitation energy diffusion and maintaining spectral consistency across varying electron transporting layer thicknesses, resulting in a more durable and efficient light emission.
Implementation Method 1
an organic electroluminescence device using iridium complexes or platinum complexes or the like as a phosphorescent material
Implementation Method 2
electrons injected from the cathode are recombined with holes injected from the anode in the light-emitting layer, to produce excitons, whose energy is utilized to luminescence
Data Source
AI summary
The organic electroluminescence device has, on a substrate thereof, a pair of electrodes and at least one organic layer including a light emitting layer between the electrodes, wherein the light emitting layer contains a phosphorescent complex material containing a specific monoanionic bidentate ligand and the device contains, in a layer sandwiched between the light emitting layer and a cathode, a compound represented by the following formula (1):(Cz)p-L-(A)q (1)wherein, Cz represents a substituted or unsubstituted arylcarbazolyl or carbazolylaryl, L represents a single bond or a substituted or unsubstituted arylene, cycloalkylene, or aromatic heterocycle, A represents a substituted or unsubstituted nitrogen-containing 6-membered aromatic heterocycle, and each of p and q independently represents an integer from 1 to 6.