Organic Electroluminescent Device with Segmented Charge Transport Layers
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Solution Overview
Problem
Conventional organic electroluminescent devices face challenges in achieving low driving voltage and high brightness while maintaining excellent light emitting efficiency, often requiring specific cathode materials and complex layer structures to reduce electron injection barriers.
Innovation Solution
The device incorporates a p-type organic material layer between the cathode and the light emitting layer and an n-type organic material layer between the p-type layer and the light emitting layer, allowing for various cathode materials and minimizing the need for electron injection layers, with the thickness of the p-type organic material layer controlling the cavity length to optimize light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional cathode materials and structures are used, then device simplicity is maintained, but driving voltage is high and brightness is limited
Solution Approach 1:
The device divides the charge transport function into separate p-type and n-type organic material layers, with the p-type layer handling hole transport and the n-type layer handling electron transport. This segmentation allows each layer to be optimized for its specific charge carrier type, reducing overall transport barriers and achieving lower driving voltage without excessive structural complexity
Solution Approach 2:
The p-type and n-type organic material layers act as intermediary layers between the electrodes and the light emitting layer. These intermediary layers facilitate charge injection and transport by providing energy level matching and reducing injection barriers, thereby lowering driving voltage while maintaining a manageable layer structure
2Reliability
If electron injection layers are added to reduce injection barriers, then light emitting efficiency improves, but device complexity increases
Solution Approach 1:
The patent combines the charge transport and charge injection functions into the p-type and n-type organic material layers. These layers simultaneously serve as charge transport pathways and injection facilitators by providing appropriate energy level alignment with the electrodes, eliminating the need for separate dedicated injection layers while maintaining high light emitting efficiency
Solution Approach 2:
The p-type and n-type organic material layers perform multiple functions: they transport their respective charge carriers (holes and electrons), provide energy level matching for charge injection from electrodes, and prevent recombination losses. This multi-functionality achieves high light emitting efficiency without adding excessive structural complexity
3Power
If specific cathode materials are required to achieve low voltage, then material selection is limited, but device performance is optimized
Solution Approach 1:
The p-type and n-type organic material layers provide localized energy level matching at the cathode interface. The p-type layer with its specific HOMO level and the n-type layer with its specific LUMO level create a tailored energy landscape that facilitates electron injection from a wide range of cathode materials, thereby achieving low driving voltage while expanding material selection flexibility
Solution Approach 2:
By adjusting the energy level parameters (HOMO and LUMO levels) of the p-type and n-type organic material layers, the device can be optimized to work with different cathode materials having various work functions. This parameter tuning capability enables low driving voltage operation across multiple cathode material choices, enhancing both performance and versatility
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
This configuration results in an organic electroluminescent device with low driving voltage, high brightness, and improved stability, enabling the use of diverse cathode materials and maintaining charge balance without increasing voltage or light absorption, thus enhancing power efficiency and device stability.
Implementation Method 1
a first electric charge transporting passage provided between the light emitting layer and the cathode, the first electric charge transporting passage including: a first p-type organic material layer which is provided between the light emitting layer and the cathode and non-doped; and a first n-type organic material layer provided between the first p-type organic material layer and the light emitting layer
Implementation Method 2
An organic electroluminescent device converts a current into visible light by injecting electrons and holes from two electrodes into an organic material layer
Data Source
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AI summary
The present specification discloses an organic electroluminescent device including: a substrate; a cathode provided on the substrate; a light emitting layer provided on the cathode; an anode provided on the light emitting layer; a first p-type organic material layer provided between the cathode and the light emitting layer; and a first n-type organic material layer provided between the first p-type organic material layer and the light emitting layer.