Charge Generation Layer Resistance for Organic EL Short Circuit Prevention
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Solution Overview
Problem
Existing organic electroluminescence (EL) display devices face issues with short circuits between electrodes and charge generation layers, leading to image quality deterioration, and the use of resistor layers increases manufacturing complexity and cost.
Innovation Solution
A display device configuration with a laminated structure that includes a charge generation layer or an electrode connection layer, which is in a high electrical resistance or insulated state in defect regions and low resistance in normal regions, preventing short circuits without the need for resistor layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a first resistive layer and a second resistive layer are disposed between the organic layer and the second electrode to prevent short circuits, then the short circuit prevention capability is improved, but the number of manufacturing steps increases and productivity decreases
Solution Approach 1:
The patent extracts the resistive layer from the structure by replacing it with a charge generation layer that inherently provides high resistance properties. The charge generation layer, formed by vacuum deposition of alkali metal or alkaline earth metal, serves both as a charge generation component and as a high-resistance barrier, eliminating the need for separate resistive layers and reducing manufacturing steps.
Solution Approach 2:
The charge generation layer performs multiple functions simultaneously: it generates charges for the organic EL element operation and provides high electrical resistance to prevent short circuits between electrodes. This multi-functional design replaces the need for separate resistive layers, simplifying the structure and improving productivity while maintaining reliability.
2Reliability
If a first resistive layer and a second resistive layer are disposed between the organic layer and the second electrode to prevent short circuits, then the short circuit prevention capability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent removes the separate resistive layer components and integrates the resistance function into the charge generation layer. This extraction of the resistance function from a separate component reduces material costs and manufacturing complexity, thereby lowering overall manufacturing cost while maintaining short circuit prevention capability.
Solution Approach 2:
The patent merges the charge generation function and the electrical resistance function into a single charge generation layer. This consolidation eliminates the need for multiple separate layers (charge generation layer plus resistive layers), reducing material usage, simplifying the manufacturing process, and decreasing production cost.
3Power
If the charge generation layer is made conductive to ensure proper charge generation, then the light emitting efficiency is improved, but short circuits between the charge generation layer and the first electrode may occur
Solution Approach 1:
The patent applies local quality by creating spatial variation in the electrical resistance of the charge generation layer. The layer maintains low resistance in normal operational regions to ensure efficient charge generation and light emission, while exhibiting high resistance in defect regions (where particles or protrusions are present) to prevent short circuits. This localized property differentiation resolves the contradiction between conductivity and short circuit prevention.
Solution Approach 2:
The charge generation layer's electrical resistance is made dynamic rather than static. The resistance automatically adjusts based on the local condition: low resistance in healthy regions for efficient operation, and high resistance in defect regions for short circuit prevention. This dynamic adaptation allows the layer to simultaneously achieve light emitting efficiency and reliability under different local conditions.
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 configuration enhances the reliability, lifespan, luminance, and display quality of organic EL devices by preventing short circuits and reducing manufacturing complexity and costs.
Implementation Method 1
the charge generation layer or an electrode connection layer which is in a high electrical resistance state or an insulated state in a defect region, while being in a low electrical resistance state in a region other than the defect region
Data Source
AI summary
A display device having light emitting elements that respectively include a first electrode formed on a substrate, a laminated structure formed on the first electrode, and a second electrode formed on the laminated structure. The laminated structure is formed by laminating, in the following order from the first electrode side, at least a first organic layer including a first light emitting layer, a charge generation layer in which a first layer into which a first carrier is injected and a second layer into which a second carrier is injected are laminated, and a second organic layer including a second light emitting layer. In a light emitting element including a defect region, the charge generation layer is in a high electrical resistance state or an insulated state in the defect region, while being in a low electrical resistance state in a region other than the defect region.