Opaque Pixel Electrode Light Blocking for TFT Reliability
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Solution Overview
Problem
In organic light emitting display devices, light emitted from the organic light emitting diode can reach the channel regions of thin film transistors, causing photo leakage current and deteriorating their driving characteristics.
Innovation Solution
The use of a substantially opaque first pixel electrode, made of materials like silver or silver alloys, is positioned to block light from reaching the thin film transistors, with a structure that overlaps the data and common power source lines, effectively preventing light from reaching the channel regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent pixel electrode is used to allow light emission, then light transmission is improved, but photo leakage current increases due to light reaching the TFT channel regions
Solution Approach 1:
An opaque shielding layer is introduced as an intermediary element between the transparent pixel electrode and the TFT channel region. This shielding layer blocks light from reaching the channel region while maintaining the transparency of the pixel electrode for light emission, thereby preventing photo leakage current without compromising illumination intensity.
Solution Approach 2:
The pixel electrode structure is segmented into multiple functional layers: a transparent conductive layer for light emission and an opaque shielding layer for light blocking. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between light transmission and photo leakage prevention.
2Reliability
If an opaque shielding layer is added to block light from reaching TFTs, then photo leakage current is reduced, but device complexity increases
Solution Approach 1:
The opaque shielding layer serves multiple functions simultaneously: it blocks light from reaching the TFT channel region to prevent photo leakage current, and it can also serve as an additional conductive layer for electrical connections. This multi-functionality reduces the need for separate dedicated shielding structures, thereby limiting the increase in device complexity.
3Object-affected harmful factors
If the opaque electrode is positioned to cover the TFT channel region, then light blocking is improved, but manufacturing precision requirements increase
Solution Approach 1:
The shielding function is achieved not only through horizontal positioning but also through vertical layering. The opaque shielding layer is placed in a different vertical dimension (z-axis) above the channel region, allowing effective light blocking even with moderate horizontal alignment tolerance, thereby reducing manufacturing precision requirements.
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 substantially prevents photo leakage current, thereby maintaining the driving characteristics of the thin film transistors and enhancing the performance of the organic light emitting display device.
Implementation Method 1
the first pixel electrode is configured to substantially block light emitting from the organic light emitting layer from reaching the thin film transistor
Data Source
AI summary
An organic light emitting display device is disclosed. One embodiment of the organic light emitting display device includes a substrate member in which a plurality of pixel regions are arranged, and a plurality of thin film transistors which are formed on the pixels regions, respectively. The device also includes a data line which is arranged along one side edge of each of the pixel region and a common power source line which is arranged along the other side edge of each of the plurality of pixel regions and is substantially parallel to the data line. The device further includes a first pixel electrode which is electrically connected to one of the plurality of thin film transistors and is formed in each region of the pixel regions. The device also includes an organic film which is formed on the first pixel electrode, and a second pixel electrode which is formed on the organic film. One side edge of the first pixel electrode which is close to the data line is overlapped with the data line.