Oxide TFT Array Light Shielding for Leakage Current Blocking
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in blocking leakage current in the off state and achieving free grayscale expression at low gray levels, particularly due to power consumption issues and current fluctuation with oxide semiconductor materials.
Innovation Solution
The use of an array substrate with a thin film transistor configuration that includes an oxide semiconductor pattern, a light shielding pattern with a semiconductor material layer, and a metal pattern, which increases the threshold voltage and s-factor, thereby blocking leakage current and enabling grayscale expression across a wide range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thin film transistor is used in an organic light emitting display device, then the device can operate with basic functionality, but leakage current cannot be effectively blocked in the off state and grayscale expression at low gray levels is limited
Solution Approach 1:
The patent changes the material parameter of the semiconductor layer from conventional materials to oxide semiconductor material, which fundamentally alters the electrical characteristics to achieve low leakage current in the off state while maintaining good on-state performance. This material parameter change enables effective leakage current blocking without requiring complex structural modifications
Solution Approach 2:
The patent employs a composite light shielding pattern structure combining semiconductor material layer and metal pattern, where the semiconductor material layer provides electrical characteristics for leakage current blocking and the metal pattern provides optical shielding. This composite approach solves both electrical and optical requirements simultaneously without increasing manufacturing complexity
2Reliability
If the threshold voltage is increased to block leakage current, then leakage current blocking improves, but the s-factor decreases limiting grayscale expression capability
Solution Approach 1:
The oxide semiconductor material enables independent optimization of threshold voltage and s-factor parameters. The material's inherent properties allow achieving high threshold voltage for leakage current blocking while simultaneously maintaining high s-factor for wide grayscale expression, breaking the conventional trade-off between these two parameters
Solution Approach 2:
The semiconductor material layer in the light shielding pattern acts as an intermediary that provides both electrical field control for threshold voltage stabilization and optical field shielding. This intermediary structure enables simultaneous achievement of high threshold voltage and high s-factor by mediating between electrical and optical requirements
3Object-affected harmful factors
If a light shielding pattern with only metal material is used, then optical shielding is achieved, but leakage current blocking and threshold voltage control are insufficient
Solution Approach 1:
The light shielding pattern is designed as a composite structure with semiconductor material layer and metal pattern. The semiconductor material layer provides electrical functionality for leakage current blocking and threshold voltage control, while the metal pattern provides optical shielding. This composite design simultaneously addresses both electrical and optical requirements without compromise
Solution Approach 2:
The semiconductor material layer in the light shielding pattern performs multiple functions: it provides optical shielding together with the metal pattern, controls threshold voltage through electrical field effects, and blocks leakage current through its semiconductor properties. This multi-functional design eliminates the need for separate structures for each function, reducing overall device complexity
Data Source
AI summary
The disclosure provides a driving thin film transistor and a switching thin film transistor each using an oxide semiconductor pattern as an active layer thereof. The driving thin film transistor and the switching thin film transistor include light shielding patterns, respectively. Each light shielding pattern includes a semiconductor material layer doped with P-type impurity ions. By virtue of the light shielding patterns including the semiconductor material layer, the driving thin film transistor and the switching thin film transistor achieve an increase in threshold voltage, thereby securing freedom of design.