White OLED Charge Generation Layer Architecture
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Solution Overview
Problem
White organic light emitting devices (OLEDs) face challenges with low light emission efficiency due to difficulties in energy transfer and excessive current application, particularly in methods involving single or multiple light emitting layers.
Innovation Solution
A white OLED structure is implemented with a charge generation layer between green, blue, and red light emitting layers, each comprising first and second layers, allowing for reduced driving current and increased light emission efficiency by optimizing current distribution across the layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light emitting layer with red, green, and blue dopants is used, then the device structure is simple, but light emission efficiency is reduced due to difficult energy transfer to dopants
Solution Approach 1:
The light emitting layer is divided into multiple separate layers, each emitting a specific color (red, green, blue). This segmentation allows each layer to be optimized for its specific wavelength, improving energy transfer efficiency to dopants while maintaining manageable device complexity through systematic layering.
Solution Approach 2:
The solution transitions from a single-layer structure to a multi-layer stacked structure, adding the dimension of vertical layering. This dimensional change enables independent optimization of each color layer's thickness and composition, resolving the energy transfer efficiency problem while organizing complexity in a structured manner.
2Manufacturing precision
If the light emitting layer is divided into multiple layers (red, green, blue), then color uniformity can be improved, but light emission efficiency is reduced due to large current applied to the light emitting layer
Solution Approach 1:
Charge generation layers are introduced as intermediary layers between the multiple light emitting layers. These intermediary layers facilitate efficient charge injection and distribution to each color layer, reducing the overall current required while maintaining uniform color emission across all layers.
Solution Approach 2:
Each light emitting layer is given specific local optimization with appropriate thickness and dopant concentration tailored to its color requirements. The charge generation layers provide localized charge injection zones, allowing each layer to operate at optimal conditions for its specific wavelength, improving both color uniformity and efficiency.
3Manufacturing precision
If multiple light emitting layers are stacked, then color accuracy can be improved, but excessive energy transfer within the light emitting layer occurs
Solution Approach 1:
The charge generation function is extracted from the light emitting layers themselves and placed in separate dedicated charge generation layers. This extraction prevents excessive energy transfer and interference within the light emitting layers, allowing each to maintain precise color characteristics without energy loss to adjacent layers.
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 achieves higher light emission efficiency and closer color coordinates to pure white, reducing driving voltage and improving overall light emitting characteristics compared to comparative examples.
Implementation Method 1
Organic light emitting devices (OLEDs) are self emissive display devices that use light generated by combining electrons and holes supplied to a fluorescence or phosphorescence organic compound thin film
Implementation Method 2
a charge generation layer arranged between the anode and the cathode and an organic layer arrangement arranged between the anode and the cathode
Data Source
AI summary
A white organic light emitting device includes an anode, a cathode, a charge generation layer arranged between the anode and the cathode and an organic layer arrangement arranged between the anode and the cathode, the organic layer arrangement including a green light emitting layer, a blue light emitting layer, and a red light emitting layer, one of the green light emitting layer, the blue light emitting layer, and the red light emitting layer includes a first light emitting layer and second light emitting layer, the charge generation layer being arranged between the first light emitting layer and the second light emitting layer.