Inorganic Hole Injection Layer for OLED Adhesion
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Solution Overview
Problem
Organic EL display devices face issues with low peeling strength and durability due to poor adhesion of the organic EL layer, particularly between the substrate and sealing film, leading to film peeling and non-light emitting areas.
Innovation Solution
Incorporating an inorganic hole injection layer with a work function of 4.4 eV or less, using materials like Na, Mg, K, Rb, Sr, Cs, Ba, Fr, Ca, Yb, Li, Al, Sm, Er, or their fluorides or oxides, and optimizing the surface roughness of the pixel electrode to enhance adhesion between the organic layer and the electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the organic EL layer is formed without a fine metal mask, then manufacturing complexity is reduced and productivity is improved, but adhesion between layers deteriorates causing peeling
Solution Approach 1:
An inorganic material layer is introduced between the pixel electrode and the organic EL layer to serve as an intermediary that enhances adhesion. This layer acts as a bridge that improves the bonding between the electrode and organic materials without requiring a fine metal mask, thus maintaining manufacturing simplicity while improving reliability.
Solution Approach 2:
The invention uses composite structures combining inorganic materials (such as metal fluorides or oxides with specific work functions) with organic EL materials. This composite approach creates a multi-layer structure that leverages the advantages of both material types to achieve both good adhesion and efficient light emission without compromising manufacturing productivity.
2Strength
If the adhesion between bank and sealing film is improved by contact, then structural integrity is enhanced, but the adhesion strength remains insufficient due to material incompatibility
Solution Approach 1:
The inorganic material layer serves as a mediator between different material systems (resin bank and silicon-based sealing film), providing a compatible interface that enhances adhesion. This intermediary layer bridges the material incompatibility between the resin bank and inorganic sealing film, enabling sufficient bonding strength.
Solution Approach 2:
The invention changes the work function parameter of the interface materials by selecting specific inorganic materials with work functions of 4.4 eV or less. This parameter change optimizes the electronic and physical properties at the interface, improving adhesion between dissimilar materials without requiring changes to the fundamental material selection.
3Ease of manufacture
If the organic EL layer is formed uniformly over the entire light emitting region, then manufacturing simplicity is achieved, but peeling resistance deteriorates due to low adhesion
Solution Approach 1:
The inorganic material layer is deposited uniformly across the entire light emitting region without requiring a fine metal mask, maintaining manufacturing simplicity. Simultaneously, this intermediary layer provides the necessary adhesion enhancement to prevent peeling, resolving the contradiction between ease of manufacture and peeling resistance.
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 solution significantly improves the peeling strength and durability of the organic EL display device, preventing film peeling and maintaining structural integrity under repeated bending, as demonstrated by increased bending resistance.
Implementation Method 1
the inorganic material has a work function of 4.4 eV or less and includes one element or a plurality of elements selected from Na, Mg, K, Rb, Sr, Cs, Ba, Fr, Ca, Yb, Li, Al, Sm, Er and Ho
Data Source
AI summary
A display device including a pixel electrode, a counter electrode, and an organic layer arranged between the pixel electrode and the counter electrode, wherein the organic layer includes a hole injection layer in contact with the pixel electrode, a hole transport layer above the hole injection layer, a light emitting layer and an electron transport layer, the hole injection layer includes an inorganic material, and the inorganic material has a work function of 4.4 eV or less and includes one element or a plurality of elements selected from Na, Mg, K, Rb, Sr, Cs, Ba, Fr, Ca, Yb, Li, Al, Sm, Er and Ho, or a fluoride or an oxide of the elements.