OLED Cathode NP Junction for Low Voltage Efficiency
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Solution Overview
Problem
Conventional organic electroluminescent devices face challenges in achieving low driving voltage and high brightness due to limitations in cathode material selection and electron injection barriers, which affect light emitting efficiency and stability.
Innovation Solution
Incorporating 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 reducing the need for electron injection layers, thereby enhancing light emitting efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional cathode materials and electron injection layers are used, then device structure is simple, but driving voltage is high and light emitting efficiency is low
Solution Approach 1:
The electron transporting layer is segmented into two distinct layers: a first electron transporting layer adjacent to the cathode and a second electron transporting layer adjacent to the light emitting layer. This segmentation allows each layer to be optimized for specific functions - the first layer focuses on electron injection from the cathode while the second layer focuses on electron transport to the light emitting layer, thereby improving overall electron injection efficiency and light emitting efficiency without requiring additional complex structures.
Solution Approach 2:
The first electron transporting layer acts as an intermediary between the cathode and the second electron transporting layer. It facilitates electron injection from the cathode into the organic material structure and transfers these electrons to the second layer, which then delivers them to the light emitting layer. This intermediary structure resolves the contradiction by improving electron injection efficiency without requiring complex additional components beyond the layered organic material structure.
2Reliability
If electron injection layers are added to improve electron injection, then light emitting efficiency improves, but device complexity increases
Solution Approach 1:
Both the first and second electron transporting layers serve multiple functions: the first layer provides electron injection from the cathode and interfaces with the second layer, while the second layer transports electrons to the light emitting layer and maintains proper energy level alignment. This multi-functionality within the two-layer structure achieves high electron injection efficiency without requiring separate dedicated electron injection layers, thus avoiding increased device complexity.
Solution Approach 2:
The invention optimizes the energy level parameters of the electron transporting layers, specifically ensuring that the LUMO level of the first electron transporting layer is lower than that of the second layer. This parameter change creates a favorable energy gradient for electron injection and transport, improving electron injection efficiency through proper energy level alignment rather than through additional structural complexity.
3Object-generated harmful factors
If cathode material selection is restricted to achieve low work function, then electron injection is improved, but material versatility is limited
Solution Approach 1:
The invention changes the energy level parameters of the electron transporting layers, specifically setting the LUMO level of the first layer lower than that of the second layer. This parameter optimization creates a favorable energy gradient that reduces the electron injection barrier at the cathode interface, allowing for improved electron injection without restricting cathode material selection to only low work function materials.
Solution Approach 2:
The first electron transporting layer serves as an intermediary between the cathode and the rest of the organic material structure. It mediates the electron injection process by providing proper energy level alignment and facilitating electron transfer from various cathode materials into the organic layers, thereby reducing the electron injection barrier while maintaining versatility in cathode material selection.
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 light emitting efficiency, enabling the use of diverse cathode materials without increasing voltage or compromising stability.
Implementation Method 1
the first n-type organic material layer and the first p-type organic material layer form an NP junction
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 an anode, a cathode, a light emitting layer provided between the cathode and the anode, 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.