OLED Charge Generation Layer Energy Level Matching
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Solution Overview
Problem
The operating voltage of multilayer organic light emitting display devices is higher than the sum of individual light emitting parts, and the lifetime is decreased due to the difference in LUMO energy levels between charge generation layers, leading to inefficiencies and performance degradation.
Innovation Solution
Incorporating an electron transport layer with a functional group for high electron mobility and a charge generation layer with a compound that matches the energy level of the electron transport layer, facilitating electron transfer and improving the interface characteristics between the layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multilayer emitting structure with N-type and P-type charge generation layers is used, then the current efficiency is doubled and charge distribution is facilitated, but the operating voltage becomes higher than the sum of individual light emitting parts
Solution Approach 1:
The patent changes the energy level parameters of the charge generation layers by selecting materials with specific LUMO and HOMO levels. The N-type charge generation layer uses a material with LUMO level of -2.5 eV to -3.5 eV, and the P-type charge generation layer uses a material with HOMO level of 5.0 eV to 6.0 eV, creating optimized energy level alignment that reduces operating voltage while maintaining high current efficiency.
Solution Approach 2:
The patent employs composite material structures where the N-type charge generation layer is combined with the P-type charge generation layer in a multilayer configuration. This composite structure integrates the advantages of both layer types, achieving enhanced charge distribution and doubled current efficiency while the specific material selection keeps the operating voltage manageable.
2Reliability
If the N-type charge generation layer is doped with alkali metal or alkali earth metal, then charge generation is enhanced, but the lifetime of the device is decreased
Solution Approach 1:
The patent changes the doping approach by selecting N-type dopants with specific properties that enhance charge generation without the harmful effects of traditional alkali metal dopants. The N-type charge generation layer uses materials doped with compounds that provide necessary charge carriers while maintaining device stability and longevity.
Solution Approach 2:
The patent replaces the traditionally used but harmful alkali metal dopants with alternative doping materials that achieve the same charge generation function without compromising device lifetime. This substitution uses materials that are equally effective for charge generation but do not cause the degradation issues associated with alkali metal doping.
3Productivity
If there is a difference in LUMO energy level between the P-type charge generation layer and the N-type charge generation layer, then charge distribution is facilitated, but electron injection from the P-type charge generation layer to the hole transport layer cannot be facilitated
Solution Approach 1:
The patent optimizes the energy level parameters by carefully selecting materials for both charge generation layers. The N-type charge generation layer uses a material with LUMO level of -2.5 eV to -3.5 eV, and the P-type charge generation layer uses a material with HOMO level of 5.0 eV to 6.0 eV, creating an energy level gradient that facilitates both charge distribution and electron injection processes.
Solution Approach 2:
The patent applies different material properties to different locations in the device structure. The N-type charge generation layer has specific LUMO level characteristics optimized for electron transport, while the P-type charge generation layer has HOMO level characteristics optimized for hole transport. This local optimization of material properties enables both charge distribution and efficient electron injection.
4Productivity
If there is a difference in LUMO energy level between the electron transport layer and the N-type charge generation layer, then electron transport is maintained, but electron injection from the N-type charge generation layer to the electron transport layer cannot be facilitated
Solution Approach 1:
The patent changes the LUMO energy level parameter of the N-type charge generation layer to be higher than that of the electron transport layer. The N-type charge generation layer uses a material with LUMO level of -2.5 eV to -3.5 eV, creating a downward energy gradient that facilitates spontaneous electron injection from the charge generation layer to the electron transport layer while maintaining efficient electron transport.
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 reduces the operating voltage and increases the lifetime of the device by enhancing electron injection and transport, leading to improved efficiency and stability.
Implementation Method 1
the electron transport layer includes an electron transport compound including a functional group with high electron mobility
Implementation Method 2
the N-type charge generation layer includes a charge generation compound including a functional group for matching the energy level of the electron transport compound
Implementation Method 3
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 4
A charge generation layer is between the first light emitting part and the second light emitting part to double the current efficiency generated in the light emitting layers and facilitate charge distribution
Data Source
Figure 1~2
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AI summary
An organic light emitting display device is disclosed. The organic light emitting display device comprising at least two or more light emitting parts each comprising a light emitting layer and an electron transport layer; and a charge generation layer between the at least two or more light emitting parts and including an N-type charge generation layer, wherein the electron transport layer includes an electron transport compound including a functional group with high electron mobility, and the N-type charge generation layer includes a charge generation compound including a functional group for matching the energy level of the electron transport compound.