Organic Electroluminescence Device Charge Generation Layer
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Solution Overview
Problem
Existing organic electroluminescence devices face challenges in achieving high luminance with reduced luminance unevenness, particularly in large-area formats, due to losses in quantum efficiency and voltage drops associated with charge generation layers.
Innovation Solution
An organic electroluminescence device with multiple light emission layers and a charge generation layer comprising p-doped and n-doped layers, along with an alkali metal layer and a hole transport material layer, is designed to enhance luminance and reduce luminance unevenness, using specific materials like Li and 4,4′,4″-tri-(2-naphthylphenylamino)-triphenylamine (2-TNATA) and arylamine compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an electric insulating layer is provided as the charge generation layer, then the device structure is simplified, but electroluminescent quantum yield is lost and emission luminance is lowered
Solution Approach 1:
The charge generation layer is constructed as a composite structure combining p-doped layer, n-doped layer, and electric insulating layer. This composite approach allows the device to achieve both simplified structure and high electroluminescent quantum yield by distributing functions across different material layers, resolving the contradiction between structural simplicity and energy efficiency
Solution Approach 2:
The charge generation layer is segmented into multiple functional sub-layers (p-doped, n-doped, and electric insulating layers) rather than using a single uniform layer. This segmentation allows each sub-layer to perform its specific function optimally, maintaining high quantum yield while keeping the overall structure manageable and systematic
2Device complexity
If an electric insulating layer is provided as the charge generation layer, then the device structure is simplified, but luminance unevenness increases particularly in large-area formats
Solution Approach 1:
The multi-layer composite charge generation structure distributes electrical properties across different layers, creating more uniform charge generation throughout the device area. This composite approach prevents the luminance unevenness that occurs with single-layer insulating structures, especially in large-area devices where uniformity is critical
Solution Approach 2:
Different sub-layers within the charge generation layer are designed with locally optimized properties - the p-doped and n-doped layers provide charge injection at specific locations, while the electric insulating layer provides field control. This local optimization of properties across the layer structure ensures uniform luminance output across the entire device area
3Illumination intensity
If multiple light emission layers are used to increase luminance, then emission luminance is improved, but device complexity increases
Solution Approach 1:
Multiple light emission layers are merged with a unified charge generation layer structure that serves all emission layers simultaneously. This combining approach allows high luminance to be achieved through multiple emitting layers while avoiding the proportional increase in complexity that would result from providing separate charge generation layers for each emission layer
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 high luminance with minimal luminance unevenness, even in large-area formats, by optimizing the charge generation and light emission layers, resulting in improved quantum efficiency and durability.
Implementation Method 1
the charge generation layer includes at least one p-doped layer and at least one n-doped layer
Implementation Method 2
further includes an alkali metal layer and a layer containing a hole transport material between the p-doped layer and the n-doped layer
Implementation Method 3
organic electroluminescence devices containing a thin film material that emits light by excitation due to application of electric current
Data Source
AI summary
An organic electroluminescence device of multi-photon emission mode which includes plural light emission layers and at least one charge generation layer between a pair of electrodes, arranged in a film thickness direction thereof, wherein the charge generation layer includes at least one p-doped layer and at least one n-doped layer, and further includes an alkali metal layer and a layer containing a hole transport material between the p-doped layer and the n-doped layer. An organic electroluminescence device of multi-photon emission mode exhibiting little unevenness in luminance even in a large-area format electroluminescence device is provided.