Driving Thin Film Transistor with Curved Channel for OLED Gray Scale Control
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Solution Overview
Problem
Organic light-emitting display devices face challenges in achieving optimal gray scale control and display quality due to the higher off-current of polycrystalline silicon transistors, which requires compensatory measures like lightly doped regions, but these measures can affect storage capacitance and resolution.
Innovation Solution
The design includes a driving thin film transistor with a semiconductor layer having a channel region with curved portions and doped regions of varying impurity concentrations, along with a storage capacitor and electrode layer with convex portions to enhance the driving range and storage capacitance, improving gray scale control and display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If polycrystalline silicon transistors are used to achieve higher electron mobility and driving range, then the driving range and gray scale control are improved, but the off-current increases and storage capacitance decreases
Solution Approach 1:
The patent applies local quality by creating lightly doped regions at specific locations between the source/drain regions and channel region, rather than uniformly doping the entire structure. This localized modification reduces off-current in critical areas while preserving the high electron mobility of polycrystalline silicon in the channel region, thus resolving the contradiction between speed and reliability.
2Reliability
If lightly doped regions are added to compensate for off-current, then the off-current is reduced, but the device complexity and manufacturing steps increase
Solution Approach 1:
The patent merges the lightly doped region formation with the existing source/drain region fabrication process. The lightly doped regions are formed simultaneously with the source and drain regions using the same doping process, eliminating the need for separate doping steps and reducing manufacturing complexity while still achieving off-current reduction.
3Measurement precision
If the channel length is increased to improve gray scale control, then the driving range is improved, but the area of the transistor increases
Solution Approach 1:
The patent employs curved portions in the channel region that extend in the width direction, effectively increasing the channel length without proportionally increasing the transistor area. This dimensional approach allows the channel to utilize the width direction for length extension, achieving improved gray scale control while minimizing area increase compared to a straight channel configuration.
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 allows for more precise control of gray scale values and improved display quality by optimizing the driving range and storage capacitance, addressing the off-current issues of polycrystalline silicon transistors while maintaining resolution.
Implementation Method 1
In operation, electron and holes injected from the electrodes recombine in the organic emission layer to form excitons. Light is emitted when the excitons change state and release energy.
Data Source
AI summary
A display device includes a switching transistor, a driving transistor, a storage capacitor connected to the switching and driving transistors, and an organic light-emitting diode connected to the driving transistor. The driving transistor is connected to the switching transistor. The driving transistor includes a semiconductor layer having a channel region, first doped regions at sides of the channel region, and second doped regions doped with impurities of a concentration greater than the first doped regions. A first electrode layer is over an insulating layer, which covers the semiconductor layer. The electrode layer includes convex portions extending toward the first doped regions and covering an end of the channel region. At least one of the convex portions has a width greater than or equal to a width of the end of the channel region.