Transparent OLED Cathode Resistance Reduction via Segmented Electrodes
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Solution Overview
Problem
Current transparent display devices face challenges in maintaining high transparency and display quality due to cathode resistance issues, which affect luminance uniformity and longevity, especially in self-light-emitting OLED displays.
Innovation Solution
The implementation of a transparent display device configuration that includes a substrate with pixels having a transparent upper electrode, a reflective lower electrode, a light-emitting film, and a thin film transistor with a channel made of transparent oxide, along with a transparent low-resistive film that interconnects the power-source potential supply line and the upper electrode, and auxiliary lines with lower sheet resistance to reduce cathode resistance and enhance transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent upper electrode is used in OLED pixels, then transparency is improved, but cathode resistance increases causing luminance non-uniformity
Solution Approach 1:
The cathode is segmented into two distinct functional regions: a transparent upper electrode for light emission and transparency, and a separate transparent low-resistive film for electrical conduction. This segmentation allows each component to optimize its specific function without compromising the other.
Solution Approach 2:
The transparent low-resistive film acts as an intermediary component between the power-source potential supply line and the transparent upper electrode. It mediates the electrical connection while maintaining transparency, solving the contradiction between conductivity and optical properties.
2Illumination intensity
If transparent oxide is used for the thin film transistor channel, then transparency is improved, but electrical conductivity decreases
Solution Approach 1:
The transparent low-resistive film is formed by changing the oxygen partial pressure during sputtering to create oxygen deficiency, which fundamentally alters the electrical conductivity parameter of the transparent oxide material while maintaining its optical transparency.
Solution Approach 2:
The device uses composite material structures where transparent oxide serves dual purposes: as a high-resistive channel layer for transistor functionality and as a low-resistive conductive film for electrical connection, achieving both transparency and conductivity requirements through different material configurations.
3Reliability
If the transparent low-resistive film is formed by sputtering with low oxygen partial pressure, then electrical conductivity is improved, but oxygen deficiency in the film increases
Solution Approach 1:
The invention deliberately changes the oxygen partial pressure parameter during sputtering to create oxygen-deficient transparent oxide films with enhanced electrical conductivity. This parameter change transforms the material properties to achieve the desired low-resistive characteristics.
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 improves luminance uniformity and extends the display's lifespan by reducing cathode resistance, maintaining high transparency, and ensuring precise image rendering while allowing the background to be visible.
Implementation Method 1
a light-emitting film disposed between the transparent upper electrode and the reflective lower electrode, the light-emitting film being configured to emit light in response to supplied electric current
Implementation Method 2
a transparent low-resistive film that is made of the transparent oxide and interconnects the power-source potential supply line and the transparent upper electrode, having a resistance lower than a resistance of the channel
Implementation Method 3
a reflective lower electrode disposed in the second region
Data Source
AI summary
Each of pixels includes: a transparent upper electrode covering at least a part of the first region and at least a part of the second region; a reflective lower electrode disposed in the second region; a light-emitting film disposed between the transparent upper electrode and the reflective lower electrode, the light-emitting film being configured to emit light in response to supplied electric current; a thin film transistor disposed lower than the reflective lower electrode in the second region, the thin film transistor having a channel made of a transparent oxide; and a transparent low-resistive film that is made of the transparent oxide and interconnects the power-source potential supply line and the transparent upper electrode, the transparent low-resistive film being separate from an oxide film that is made of the transparent oxide and includes the channel and having a resistance lower than a resistance of the channel.