Tungsten Oxide Hole Injection Layer for Organic EL Stability
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Solution Overview
Problem
The manufacturing of large-sized organic EL panels using vapor deposition-type organic EL elements is challenging due to precision issues with mask position adjustment, and application-type elements face problems with hole injection layer stability and efficiency during processing.
Innovation Solution
An organic EL element with a hole injection layer composed of tungsten oxide, having an occupied energy level 1.8 eV to 3.6 eV lower than the lowest energy level of the valence band, which enhances hole injection efficiency and stability, allowing for low-voltage operation and resistance to degradation during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vapor deposition-type organic EL elements are used for large-sized panels, then light-emitting efficiency and operating lifetime are improved, but mask position adjustment precision deteriorates due to thermal expansion differences
Solution Approach 1:
The patent changes the material parameter of the hole injection layer from conventional organic materials to tungsten oxide, which has different thermal expansion properties. This parameter change makes the hole injection layer less sensitive to thermal expansion differences during mask alignment, thereby maintaining manufacturing precision for large-sized panels while preserving the reliability benefits of vapor deposition-type elements.
2Productivity
If application-type organic EL elements are used for large-sized panels, then manufacturing scalability is improved, but hole injection layer stability deteriorates during processing
Solution Approach 1:
The patent changes the material composition parameter of the hole injection layer to tungsten oxide, which exhibits superior chemical stability and resistance to degradation during wet processing steps. This parameter change enables the hole injection layer to maintain its stability throughout the manufacturing process, making application-type elements suitable for large-scale production without compromising layer integrity.
3Ease of manufacture
If conventional hole injection layers are used, then ease of manufacture is maintained, but hole injection efficiency deteriorates requiring higher driving voltage
Solution Approach 1:
The patent changes the energy level parameter of the hole injection layer material to tungsten oxide, which has appropriate HOMO level alignment with the functional layer. This parameter change reduces the hole injection barrier height, improving hole injection efficiency and enabling low-voltage operation, thereby reducing electrical consumption while maintaining ease of manufacture through standard deposition processes.
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 tungsten oxide in the hole injection layer reduces the hole injection barrier, enabling efficient hole injection and maintaining performance throughout the manufacturing process, facilitating the production of large-sized organic EL panels with improved light-emitting efficiency and low electrical consumption.
Implementation Method 1
The emission of light from the organic EL element is caused by an electric-field light-emitting phenomenon taking place as a result of the recombination of holes which are injected from the anode to the functional layer, and the electrons which are injected from the cathode to the functional layer.
Data Source
AI summary
An organic light-emitting element includes an anode, a functional layer, and a hole injection layer between the anode and the functional layer. The functional layer contains an organic material. The hole injection layer injects holes to the functional layer. The hole injection layer comprises tungsten oxide and includes an occupied energy level that is approximately 1.8 electron volts to approximately 3.6 electron volts lower than a lowest energy level of a valence band of the hole injection layer in terms of binding energy.