OLED Charge Generation Layer Using Nitrogen Compounds
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Solution Overview
Problem
Organic light emitting display devices with multilayer emitting structures face issues of higher operating voltage and decreased efficiency due to the use of N-type charge generation layers doped with alkali metals, which can lead to reduced lifetime and increased voltage when electrons move between layers with differing LUMO energy levels.
Innovation Solution
Incorporating a compound with multiple nitrogen atoms and a substituent of high electron mobility, represented by Chemical Formula 1, in the electron transport and charge generation layers to facilitate efficient electron transfer and reduce operating voltage, while maintaining or improving light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an N-type charge generation layer doped with alkali metal or alkali earth metal is used, then charge distribution is facilitated, but device lifetime is decreased
Solution Approach 1:
The patent changes the chemical composition parameters of the charge generation layer by using undoped organic compounds with specific molecular structures (containing electron-donating groups like amino or hydroxyl groups). This parameter change eliminates the need for alkali metal doping while maintaining charge generation capability, thus improving device lifetime without sacrificing charge distribution functionality
Solution Approach 2:
The patent replaces the unstable doped charge generation layer (short-lived due to metal degradation) with stable undoped organic compounds. Although undoped layers may seem less effective initially, the patent shows they provide long-term stable operation, effectively replacing a short-lived component with a durable one
2Ease of operation
If the LUMO energy level difference between P-type and N-type charge generation layers is reduced, then electron injection is improved, but operating voltage increases
Solution Approach 1:
The patent extracts the N-type charge generation layer from the device structure entirely, eliminating the LUMO energy level mismatch problem between P-type and N-type layers. By removing the problematic component (N-type doped layer), the patent avoids electron injection issues while preventing operating voltage increase through alternative charge generation mechanisms using undoped materials
Solution Approach 2:
The patent introduces undoped organic compounds with specific molecular structures as intermediary materials between the P-type charge generation layer and the light-emitting layer. These intermediary materials facilitate charge generation and transport through their inherent molecular properties (electron-donating groups) without requiring doping, thus mediating the charge transfer process without creating LUMO energy level barriers
3Reliability
If a multilayer emitting structure with blue fluorescent and yellow phosphorescent layers is used, then device lifetime is improved, but operating voltage increases and efficiency decreases
Solution Approach 1:
The patent changes the material parameters of the charge generation layers by using undoped organic compounds with specific molecular structures containing electron-donating groups. This parameter change reduces charge transfer resistance and improves charge injection efficiency, thereby reducing operating voltage while maintaining the multilayer emitting structure's long lifetime advantage
Solution Approach 2:
The patent uses composite material design in the charge generation layers, combining P-type and undoped organic materials with complementary properties. The P-type layer provides hole generation while the undoped layer with electron-donating groups provides electron generation and transport, creating a synergistic composite system that improves overall device efficiency and reduces operating voltage
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 use of these compounds in the organic light emitting display devices results in a relative reduction in operating voltage and an increase in light emission efficiency, addressing the issues of lifetime and voltage stability by enhancing electron injection and transport properties.
Implementation Method 1
the compound is represented by Chemical Formula 1... a compound having one or more nitrogen atoms and a substituent with relatively high electron mobility... facilitates electron transfer from the organic layer to the light emitting layer
Implementation Method 2
OLED devices are a type of devices that emit light as electrons and holes are paired and then extinguished, when a charge is injected into an organic light emitting layer between an anode and a cathode
Implementation Method 3
a second light emitting part using a yellow phosphorescent diode as a light emitting layer... yellow light emitted from the yellow phosphorescent diode
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
An organic light emitting display device (100) is disclosed. The organic light emitting display device comprising at least one light emitting part (ST1, ST2, ST3) between an anode (110) and a cathode (220), comprising at least one organic layer and a light emitting layer (150, 190, 250), wherein the at least one organic layer includes a compound having one or more nitrogen atoms and a substituent with relatively high electron mobility.