Transparent Cathode Structure for OLED Light Transmittance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Top emission type organic light emitting devices face limitations in achieving high light transmittance due to the low light transmittance of conventional metal cathodes, which complicates the manufacturing process and requires complex micro-cavity structures for color variation, making it difficult to scale for large area displays.
Innovation Solution
A cathode structure comprising a buffer layer, a metal oxide layer, and a metal layer with a lower work function than the anode, along with an electron injection layer and an intermediate layer, is used to enhance light transmittance without the need for a micro-cavity structure, allowing for improved light emission efficiency and simplified manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional metal cathode is used to achieve low work function, then electron injection is improved, but light transmittance deteriorates
Solution Approach 1:
The cathode is divided into multiple functional layers: a first cathode layer (metal with low work function) for electron injection and a second cathode layer (transparent conductive oxide) for light transmittance. This segmentation allows each layer to specialize in one function, resolving the contradiction between electron injection and light transmission.
Solution Approach 2:
The cathode uses a composite structure combining metal materials (for low work function) with transparent conductive oxide materials (for high light transmittance). This composite approach allows the system to simultaneously achieve both low work function and high transparency that cannot be obtained with single materials.
2Power
If a micro-cavity structure is added to amplify light emission, then light emission efficiency is improved, but device complexity increases
Solution Approach 1:
The invention extracts and removes the micro-cavity resonance structure from the device, achieving light emission amplification through the cathode's optical cavity effect alone. This eliminates the need for complex additional structures while maintaining light emission efficiency.
Solution Approach 2:
The cathode structure serves multiple functions simultaneously: it provides electron injection (through low work function metal), ensures light transmittance (through transparent conductive oxide), and achieves light amplification (through optical cavity effect). This multi-functionality eliminates the need for separate micro-cavity structures.
3Illumination intensity
If independent masks are used for each color to vary organic layer thickness, then color-specific optical efficiency is improved, but manufacturing process complexity increases
Solution Approach 1:
The invention changes the approach from varying physical thickness parameters (requiring independent masks) to varying optical properties through material selection and cathode structure design. This allows color-specific optimization without increasing manufacturing complexity.
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 proposed cathode structure achieves over 85% light transmittance and suitable electrical characteristics, increasing light emitting efficiency and simplifying the manufacturing process, while eliminating the need for micro-cavity structures, thus addressing the limitations of conventional top emission devices.
Implementation Method 1
a metal layer (41) including a metal having an absolute work function value lower than an absolute work function value of the anode material
Implementation Method 2
light is emitted by exitons formed by recombination of holes injected from the anode and electrons injected from the cathode in the organic light emitting layer
Implementation Method 3
a cathode on the organic layer and through which light emitted from the light emitting layer passes, wherein the cathode includes: a buffer layer, a metal oxide layer including a metal oxide, and a metal layer including a metal
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An organic light emitting device is provided that includes: an anode including an anode material and for injecting holes; an organic layer including a light emitting layer on the anode; and a cathode on the organic layer and through which light emitted from the light emitting layer passes, wherein the cathode includes: a buffer layer, a metal oxide layer including a metal oxide, and a metal layer including a metal having an absolute work function value lower than an absolute work function value of the anode material and coupled to the buffer layer and the metal oxide layer.