Nickel Hydroxide Hole Injection Layer for Low-Temperature OLEDs
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Solution Overview
Problem
Light-emitting elements with hole injection layers made of p-type transition metal oxides, such as nickel oxide, suffer from inadequate hole injection and transport capabilities, and require high-temperature heat treatments, making it difficult to form these layers on substrates with thin film transistor layers without thermal damage.
Innovation Solution
A light-emitting element structure that includes a nickel hydroxide layer between the anode and the light-emitting layer, which can be formed at lower temperatures, providing improved hole transport capabilities without the need for high-temperature heat treatments, and can be used in a display device with multiple light-emitting elements of different peak wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nickel oxide film is used as hole injection layer to improve reliability, then reliability is improved, but hole injection capability and hole transport capability deteriorate
Solution Approach 1:
The patent introduces an organic hole transport layer as an intermediary between the nickel oxide hole injection layer and the light-emitting layer. This mediator layer compensates for the poor hole transport capability of nickel oxide by providing efficient hole transport pathways, thereby maintaining both reliability (through nickel oxide) and hole transport performance (through the organic layer).
Solution Approach 2:
The patent creates a composite structure combining inorganic nickel oxide with organic hole transport materials. This composite approach leverages the high reliability of inorganic materials while compensating for their poor hole transport capabilities using organic materials with excellent charge transport properties.
2Reliability
If nickel oxide film is used as hole injection layer to improve reliability, then reliability is improved, but light-emitting element characteristics deteriorate
Solution Approach 1:
The organic hole transport layer acts as a mediator that interfaces between the nickel oxide layer and the light-emitting layer, ensuring efficient charge transfer and maintaining excellent light-emitting element characteristics while preserving the reliability benefits of nickel oxide.
Solution Approach 2:
The composite structure of nickel oxide and organic hole transport materials enables both high reliability and excellent light-emitting characteristics by combining the strengths of inorganic and organic materials.
3Ease of manufacture
If high temperature heat treatment is applied to form nickel oxide film, then nickel oxide film can be formed, but thermal damage to thin film transistor layer occurs
Solution Approach 1:
The patent changes the formation parameters of the nickel oxide layer by using low-temperature sputtering followed by low-temperature heat treatment (below 200°C), replacing the conventional high-temperature formation method. This parameter change enables nickel oxide film formation without causing thermal damage to the thin film transistor layer.
Solution Approach 2:
The patent replaces the thermal conversion method (heating) with sputtering deposition followed by low-temperature treatment, substituting a mechanical/physical deposition process for the thermal chemical conversion process, thereby avoiding high-temperature damage.
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 nickel hydroxide layers in light-emitting elements enhances reliability and performance while allowing for the formation of display devices without high-temperature processing, ensuring satisfactory light-emitting characteristics and reducing thermal stress on the thin film transistor layers.
Implementation Method 1
a layer made of nickel hydroxide, the layer being provided between the anode and the light-emitting layer
Data Source
AI summary
A light-emitting element includes an anode, a cathode, a light-emitting layer provided between the anode and the cathode, and a hole injection layer made of nickel hydroxide, the hole injection layer being provided between the anode and the light-emitting layer.