Stacked OLED Cathode Interface for Low Driving Voltage
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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
A stacked organic electroluminescent device structure is introduced, featuring a cathode, anode, and light emitting units with a first n-type organic material layer on the cathode side of the light emitting layer and a first p-type organic material layer between the light emitting units and the cathode, allowing for the use of various cathode materials and eliminating the need for electron injection layers, thereby reducing the electron injection barrier.
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 complete, but driving voltage is high and light emitting efficiency is low
Solution Approach 1:
The patent removes the electron injection layer from the device structure, extracting this component that was causing high driving voltage. The electron injection function is instead achieved through the optimized energy level alignment between the cathode and the adjacent organic material layer, eliminating the need for a separate injection layer and reducing overall device complexity.
Solution Approach 2:
The patent changes the energy level parameters of the cathode material, selecting a cathode with a work function that matches the LUMO level of the adjacent organic material layer. This parameter optimization enables efficient electron injection without requiring additional layers, thereby reducing driving voltage while maintaining structural simplicity.
2Illumination intensity
If conventional electron injection layers are used, then electron injection is facilitated, but device brightness and light emitting efficiency are reduced
Solution Approach 1:
The patent extracts the electron injection layer from the device architecture, eliminating the component that was limiting brightness and efficiency. Electron injection is achieved directly through the cathode-organic material interface by optimizing their energy level alignment, particularly matching the cathode work function with the organic material LUMO level.
Solution Approach 2:
The patent employs a composite interface structure where the cathode material is specifically selected to have energy level compatibility with the adjacent organic material layer. This composite approach at the interface enables efficient electron injection and high brightness without requiring a separate electron injection layer.
3Adaptability or versatility
If cathode material selection is restricted, then electron injection barrier is reduced, but material versatility is limited
Solution Approach 1:
The patent establishes a parameter-based selection criterion for cathode materials, where the work function of the cathode should match the LUMO level of the adjacent organic material layer. This parameter optimization reduces the electron injection barrier while providing versatility in cathode material selection, as multiple materials can satisfy this energy level matching condition.
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 a device with low driving voltage, high brightness, and improved light emitting efficiency, as well as increased stability and flexibility in selecting cathode materials, without the need for additional electron injection layers or doping.
Implementation Method 1
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; and two or more light emitting units provided between the anode and the cathode and including a light emitting layer, in which a light emitting unit among the light emitting units, which is the most associated with the cathode, includes a first n-type organic material layer provided on the cathode side of the light emitting layer, and a first p-type organic material layer is provided between the light emitting unit among the light emitting units, which is the most associated with the cathode, and the cathode.