Stacked OLED Charge Generation Layers for Voltage Stability
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Solution Overview
Problem
Organic electroluminescent devices face challenges in achieving improved operating voltage stability and current efficiency over time.
Innovation Solution
The use of an organic electroluminescent device structure comprising an anode layer, cathode layer, organic semiconductor layer, and multiple light-emitting units with independently positioned charge generation layers, where the organic semiconductor layer is closer to the anode and includes a compound of formula (I), and the charge generation layers, particularly a p-type charge generation layer, comprise an organic hole transport material and a compound of formula (II).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional OLED structure with HTL, EML, and ETL layers is used, then the device can achieve basic light emission functionality, but the operating voltage stability and current efficiency deteriorate over time
Solution Approach 1:
The device is divided into multiple light-emitting units (first, second, third light-emitting units) with independent charge generation layers positioned between them. This segmentation allows each unit to be independently optimized and controlled, improving overall device reliability and stability over time while addressing the lifetime issue through modular architecture.
Solution Approach 2:
Charge generation layers are introduced as intermediary components between the light-emitting units. These layers facilitate balanced charge injection and transport, improving both operating voltage stability and current efficiency while extending device operational lifetime through enhanced charge management.
2Productivity
If the organic semiconductor layer is positioned closer to the anode, then hole injection and transport are improved, but electron transport and balance become more difficult to achieve
Solution Approach 1:
The device is divided into multiple light-emitting units with independent charge generation layers. This segmentation allows optimization of hole injection in the organic semiconductor layer closer to the anode while maintaining charge balance through separate electron transport pathways in each unit.
Solution Approach 2:
Charge generation layers serve as intermediaries that facilitate balanced charge transport between the organic semiconductor layer and the light-emitting units, ensuring both high current efficiency and proper charge balance are achieved simultaneously.
3Reliability
If multiple light-emitting units are stacked with charge generation layers between them, then operating voltage stability and current efficiency are improved, but device structure complexity increases
Solution Approach 1:
The device is segmented into multiple light-emitting units with charge generation layers between them. This segmentation improves operating voltage stability and current efficiency while the modular nature of the units helps manage structural complexity through repeatable design elements.
Solution Approach 2:
The charge generation layers serve multiple functions: they facilitate charge injection, improve voltage stability, enhance current efficiency, and act as interfaces between light-emitting units. This multi-functionality reduces the need for additional separate components, managing overall device complexity.
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 enhances operating voltage stability and current efficiency, leading to superior performance compared to traditional organic electroluminescent devices.
Implementation Method 1
holes injected from the anode move to the EML, via the HTL, and electrons injected from the cathode move to the EML, via the ETL
Implementation Method 2
The holes and electrons recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted
Data Source
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AI summary
The present invention relates to an electroluminescent device comprising a compound of formula (I) and a compound of formula (II), and a display device comprising the organic electroluminescent device.