Silver Reflective OLED with Graded Inorganic Layers
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in reducing driving voltage while maintaining or improving light emission efficiency, which affects the lifespan of the devices.
Innovation Solution
The implementation of a reflective layer made of silver or silver alloy, an inorganic layer with a lower work function, an emission layer, and an organic layer, along with a second electrode, where the inorganic layer includes a first and second inorganic layer with specific materials and work functions to enhance electron transport and injection, and a transparent electrode layer to improve light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a reflective layer made of silver or silver alloy is used, then light emission efficiency is improved, but device complexity increases due to additional layers
Solution Approach 1:
The inorganic layer is divided into multiple sub-layers (first inorganic layer with work function 3.0-4.0 eV, second inorganic layer with work function 2.0-3.0 eV) to progressively reduce the work function and facilitate electron injection, while the reflective layer is segmented into silver-based layers with specific thicknesses (50-200 nm) to optimize light reflection. This segmentation allows each layer to perform its specific function efficiently, resolving the contradiction between improved light emission and device complexity.
Solution Approach 2:
The patent employs composite material structures including silver or silver alloy reflective layers combined with specific inorganic materials (such as zinc oxide, indium oxide, or their doped variants) to create a multi-functional emission layer stack. The composite structure leverages the high reflectivity of silver while the inorganic composite layers provide tailored work function characteristics, achieving enhanced light emission efficiency without excessive complexity increase.
2Power
If the work function of the inorganic layer is reduced to enhance electron injection, then driving voltage is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent systematically changes the work function parameter of the inorganic layer by selecting materials with specific work function ranges (first inorganic layer: 3.0-4.0 eV, second inorganic layer: 2.0-3.0 eV) and controlling their thicknesses (first layer: 50-200 nm, second layer: 10-50 nm). These parameter changes enable progressive electron injection facilitation, reducing driving voltage while maintaining manufacturability through well-defined material specifications.
Solution Approach 2:
The inorganic layer structure implements local quality by having different regions (sub-layers) with distinct work function characteristics. The first inorganic layer has a higher work function (3.0-4.0 eV) positioned closer to the reflective layer, while the second inorganic layer has a lower work function (2.0-3.0 eV) closer to the emission layer. This local differentiation optimizes electron injection at each interface, reducing overall driving voltage without requiring extreme manufacturing precision across the entire structure.
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 reduces driving voltage and enhances light emission efficiency, thereby extending the lifespan of the display device.
Implementation Method 1
an inorganic layer on the reflective layer, the inorganic layer having a work function that is lower than that of the reflective layer
Implementation Method 2
the inorganic layer may include a first inorganic layer and a second inorganic layer, the first inorganic layer may include a material having a work function that is lower than that of the reflective layer, and the second inorganic layer may have a work function that is lower than that of the first inorganic layer
Implementation Method 3
a reflective layer on a first electrode, the reflective layer including silver or a silver alloy
Implementation Method 4
An electron injected from one electrode and a hole injected from the other electrode may be coupled with each other in the emission portion to generate an exciton, and the exciton may emit energy in the form of light
Data Source
AI summary
A display device includes a reflective layer on a first electrode, the reflective layer including silver or a silver alloy, an inorganic layer on the reflective layer, the inorganic layer having a work function that is lower than that of the reflective layer, an emission layer on the inorganic layer, an organic layer on the emission layer, and a second electrode on the organic layer.