Multi-Emission OLED Electron Transport Stack for Lower Driving Voltage
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Solution Overview
Problem
Multi-emission-layer organic light-emitting diodes (OLEDs) face challenges in improving driving voltage performance, particularly for top emission OLEDs, where balanced injection and flow of holes and electrons are crucial for efficiency but not adequately addressed by existing technologies.
Innovation Solution
An OLED structure incorporating a first emission layer, a second emission layer, a first charge generation layer, and a first electron transport layer stack, where the first charge generation layer is between the emission layers, and the first electron transport layer stack includes a compound of Formula (I) and a second electron transport layer comprising a compound of Formula (II), both free of electrical dopants, to enhance electron injection and reduce driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional electron transport materials are used in multi-emission-layer OLEDs, then the device structure can be maintained, but the driving voltage performance remains insufficient
Solution Approach 1:
The patent changes the chemical structure parameters of electron transport materials by introducing specific substituents (fluorine atoms, cyano groups, trifluoromethyl groups) at defined positions in the molecular structure. This modifies electronic properties such as LUMO energy levels and electron mobility, enabling improved electron injection and reduced driving voltage while maintaining device structure reliability
Solution Approach 2:
The patent employs composite electron transport layer structures where different electron transport materials are combined in specific configurations (e.g., first electron transport layer with second electron transport layer). Each layer uses materials with complementary properties to achieve synergistic effects in electron injection and transport, resolving the contradiction between voltage reduction and injection efficiency
2Illumination intensity
If multi-emission-layer structure is implemented, then color performance and brightness can be improved, but driving voltage increases and efficiency decreases
Solution Approach 1:
The patent applies local quality by assigning different electron transport materials to different regions/layers of the electron transport system. Each layer is optimized with specific materials (e.g., first electron transport layer near the first emission layer, second electron transport layer near the second emission layer) to locally enhance electron injection efficiency at each emission interface, thereby reducing overall driving voltage while maintaining multi-emission brightness performance
Solution Approach 2:
The electron transport system is segmented into multiple distinct layers (first electron transport layer, second electron transport layer) with different material compositions and functions. This segmentation allows independent optimization of electron transport properties at different depths, enabling efficient electron supply to multiple emission layers without excessive voltage increase
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 proposed OLED structure improves electron injection and reduces driving voltage, leading to increased current efficiency and performance in multi-emission-layer OLEDs.
Implementation Method 1
the first electron transport layer comprises a compound of Formula (I)... to enhance electron injection and reduce driving voltage
Implementation Method 2
the second electron transport layer comprises a compound of Formula (II)... The injection and flow of holes and electrons should be balanced, so that an OLED having the above-described structure has excellent efficiency
Implementation Method 3
the first charge generation layer is arranged between the first emission layer and the second emission layer... The injection and flow of holes and electrons should be balanced
Implementation Method 4
When a voltage is applied to the anode and the cathode, holes injected from the anode electrode move to the EML, via the HTL, and electrons injected from the cathode electrode move to the EML, via the ETL. 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
Figure 1
Figure 2A~2C
AI summary
The present invention relates to an organic light emitting diode comprising an anode, a cathode, a first emission layer, a second emission layer, a first charge generation layer and a first electron transport layer stack; and to a display device or lighting device comprising the same.