Phthalocyanine Electron-Relay Layer for Low-Voltage OLEDs
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Solution Overview
Problem
Light-emitting elements with charge-generation layers containing metal oxides require high voltage for electron injection due to high injection barriers, leading to increased power consumption and reduced luminance.
Innovation Solution
A light-emitting element structure with multiple EL layers, including a charge-generation region with an acceptor substance, a phthalocyanine-based electron-relay layer, and an alkali metal-containing electron-transport layer, which lowers the electron injection barrier, allowing for low-voltage operation and high luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge-generation layer containing metal oxide is used, then charge generation is achieved, but high injection barrier requires high voltage leading to increased power consumption
Solution Approach 1:
An electron-relay layer containing a phthalocyanine-based material is introduced between the charge-generation layer and the EL layer. This intermediary layer facilitates electron transfer from the charge-generation layer to the EL layer, reducing the injection barrier and enabling low-voltage operation while maintaining charge generation capability
Solution Approach 2:
The charge-generation layer is formed as a composite containing both an acceptor substance and a hole-transport substance, optimizing both charge generation and hole transport functions. Additionally, the electron-relay layer uses phthalocyanine-based materials with specific LUMO levels to create an efficient electron transfer pathway
2Reliability
If a charge-generation layer containing metal oxide is used, then charge generation is achieved, but high injection barrier reduces luminance efficiency
Solution Approach 1:
The electron-relay layer acts as a mediator that enables efficient electron injection into the EL layer, ensuring sufficient electron supply for high-luminance operation while the charge-generation layer maintains its charge generation function
Solution Approach 2:
The LUMO level of the electron-relay layer is specifically controlled to be between -5.0 eV and -3.0 eV, optimizing the energy level alignment for efficient electron transfer. This parameter optimization ensures both high luminance and low driving voltage
3Reliability
If high voltage is applied to overcome injection barrier, then electron injection is improved, but power consumption increases
Solution Approach 1:
The electron-relay layer with optimized LUMO level serves as an intermediary that reduces the energy barrier for electron injection, enabling efficient electron transfer at low voltages and thereby reducing power consumption while maintaining injection efficiency
Solution Approach 2:
By controlling the LUMO level of the electron-relay layer to be between -5.0 eV and -3.0 eV, the energy barrier for electron injection is reduced, allowing efficient electron transfer at low driving voltages and reducing overall power consumption
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 structure enables efficient electron injection and transport, reducing the driving voltage while maintaining high luminance, thus lowering power consumption and improving the light-emitting element's performance.
Implementation Method 1
The second layer is provided between the first layer and the third layer, is in contact with the first layer and the third layer, and is formed of a phthalocyanine-based material
Implementation Method 2
The first layer is provided between the (m+1)th EL layer and the second layer, is in contact with the (m+1)th EL layer and the second layer, functions as a charge-generation region, has hole-transport properties, and contains an acceptor substance
Implementation Method 3
The third layer is provided between the second layer and the m-th EL layer, is in contact with the second layer and the m-th EL layer, has electron-transport properties, and contains an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal compound, an alkaline earth metal compound, or a rare earth metal compound
Data Source
AI summary
A light-emitting element that emits light with high luminance and can be driven at low voltage. The light-emitting element includes n (n is a natural number greater than or equal to 2) EL layers between an anode and a cathode, and includes a first layer, a second layer, and a third layer between an m-th (m is a natural number, 1≦m≦n−1) EL layer from the anode and an (m+1)th EL layer. The first layer functions as a charge-generation region, has hole-transport properties, and contains an acceptor substance. The third layer has electron-transport properties and contains an alkali metal or the like. The second layer is formed of a phthalocyanine-based material and is provided between the first layer and the third layer, whereby an injection barrier at the time of injecting electrons generated in the first layer into the m-th EL layer through the third layer can be lowered.