Metal Oxide Hole Injection Layer for Low-Voltage Organic EL Panels
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Solution Overview
Problem
The formation of metal oxide films for organic EL display panels at low substrate temperatures results in amorphous structures with reduced diffusion and non-uniform composition, leading to high driving voltage requirements due to low hole conduction efficiency, and the use of hole injection layers on auxiliary wiring increases resistance and manufacturing costs.
Innovation Solution
A metal oxide film with both metal atoms at maximum and less than maximum valence, forming a crystal structure with nanometer-sized particles, is used as a continuous hole injection layer above both the electrode and auxiliary wiring, facilitating efficient hole conduction and reducing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If metal oxide film is formed at low substrate temperature, then formation process is simpler and manufacturing cost is reduced, but the film structure becomes amorphous with reduced diffusion and non-uniform composition, leading to high driving voltage
Solution Approach 1:
The patent applies parameter changes by controlling the substrate temperature within a specific range (100°C to 300°C) and adjusting the metal oxide composition ratio to achieve a crystalline structure with uniform composition. This resolves the contradiction by finding optimal parameter values that enable crystal formation at relatively low temperatures while maintaining uniform composition and achieving low driving voltage.
Solution Approach 2:
The patent uses composite materials by creating a metal oxide film with specific crystalline structures and controlled composition ratios. The film is designed as a composite of metal atoms at different valence states, which enables both easy formation and low driving voltage operation through enhanced hole conduction efficiency.
2Reliability
If hole injection layer is provided on auxiliary wiring, then electrical connection is improved, but resistance increases and manufacturing cost increases
Solution Approach 1:
The patent applies universality by making the metal oxide film serve multiple functions: it acts as both the hole injection layer for the organic EL element and as the connection layer for the auxiliary wiring. This eliminates the need for a separate hole injection layer on the auxiliary wiring, reducing manufacturing steps and costs while maintaining reliable electrical connection and low resistance.
3Ease of manufacture
If metal oxide film has amorphous structure with reduced diffusion, then formation at low temperature is easier, but hole conduction efficiency is reduced
Solution Approach 1:
The patent changes the structural parameter of the metal oxide film from amorphous to crystalline by controlling the substrate temperature and composition ratio. This crystalline structure with uniform composition enables efficient hole conduction through the material while still being formable at relatively low temperatures, resolving the contradiction between ease of manufacture and hole conduction efficiency.
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 solution reduces the driving voltage and enhances light-emitting efficiency while maintaining low resistance in the wiring portion and stability of the hole injection layer, enabling cost-effective and efficient manufacturing.
Implementation Method 1
metal atoms constituting the metal oxide include both metal atoms at a maximum valence thereof and metal atoms at a valence less than the maximum valence
Implementation Method 2
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 injected from the anode to the functional layer and electrons injected from the cathode to the functional layer
Data Source
AI summary
Provided is organic EL display panel and an organic EL display apparatus that can be driven at a low voltage and that exhibit excellent light-emitting efficiency. Included are a substrate, a first electrode, an auxiliary wiring, a hole injection layer, a functional layer, and a second electrode. The hole injection layer and the second electrode are formed to be continuous above the first electrode and above the auxiliary wiring. The second electrode and the auxiliary wiring are electrically connected by the hole injection layer in an organic EL display panel. The hole injection layer is a metal oxide film, and metal atoms constituting the metal oxide include both metal atoms at a maximum valence thereof and metal atoms at a valence less than the maximum valence. The metal oxide film includes a metal oxide crystal with a particle diameter on the order of nanometers.