White Organic EL Device Polymer Layers
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Solution Overview
Problem
Existing white organic electroluminescent (EL) devices face challenges in controlling the diffusion of excitons and thickness of layers, particularly in two-wavelength type devices using low molecular weight materials, which affects the efficiency and white balance of the emitted light.
Innovation Solution
A white organic EL device is developed using polymer light-emitting layers formed by a wet process, with specific energy levels and band gaps for each layer, allowing for easy control of thickness and adjustment of white balance, comprising a first polymer light-emitting layer with a HOMO energy level between 5.0 eV and 5.4 eV, a second layer with a higher energy level, and optionally a third layer, to achieve stable and efficient white light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If low molecular weight materials are used to manufacture white organic EL devices, then the device structure can be simplified, but it becomes difficult to control the diffusion of excitons and the thickness of each layer
Solution Approach 1:
The patent changes the molecular weight parameter of the light-emitting materials from low molecular weight to high molecular weight polymer materials. This parameter change enables better control over layer thickness and exciton diffusion while maintaining device functionality. The polymer materials allow for precise thickness control through solution processing and provide sufficient exciton confinement for efficient light emission.
Solution Approach 2:
The patent employs composite material structures by combining multiple polymer light-emitting layers with different energy levels. The device includes a first polymer light-emitting layer with HOMO energy level of 5.0-5.4 eV and a second polymer light-emitting layer with higher HOMO energy level, creating a composite structure that achieves both manufacturing control and high efficiency through the synergistic arrangement of different materials.
2Illumination intensity
If multiple light-emitting layers are stacked to achieve white light emission, then color performance improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent uses solution processing methods for manufacturing the polymer light-emitting layers, which simplifies the fabrication process compared to traditional vacuum deposition techniques. The solution-based approach allows for easier control of layer thickness and composition, making the multi-layer structure more manufacturable while maintaining excellent color performance.
Solution Approach 2:
The patent employs composite material structures by combining multiple polymer light-emitting layers with different energy levels. The device includes a first polymer light-emitting layer with HOMO energy level of 5.0-5.4 eV and a second polymer light-emitting layer with higher HOMO energy level, creating a composite structure that achieves both manufacturing control and high efficiency through the synergistic arrangement of different materials.
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 solution enables precise control of white balance and color performance, achieving excellent color stability and efficiency by adjusting the thickness of the polymer light-emitting layers, resulting in desirable white color emission with high purity and low turn-on voltage.
Implementation Method 1
white organic electroluminescent (EL) device including a first polymer light-emitting layer and a second polymer light-emitting layer
Data Source
AI summary
Provided is a white organic electroluminescent (EL) device including multiple polymer light emitting layers. a white organic electroluminescent device includes a first polymer light-emitting layer and a second polymer light-emitting layer, both of which are formed between a first electrode and a second electrode. A highest occupied molecular orbital (HOMO) energy level of the first polymer light-emitting layer is in the range 5.0 eV through 5.4 eV, and a HOMO energy level of the second polymer light-emitting layer is higher than the HOMO energy level of the first polymer light-emitting layer. Colors emitted from both of the first and second polymer light-emitting layers are combined to produce a white color.