Display Substrate Demultiplexer TFTs for Stable On-State Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional display substrates face a decrease in on-state current due to a rise in threshold voltage of thin-film transistors in demultiplexer circuits, caused by high positive bias and electron trapping, which affects the efficiency of image signal distribution to pixel electrodes.
Innovation Solution
The display substrate incorporates a demultiplexer circuit with switch TFTs having a double-gate structure and reduced gate length, along with a common electrode shared with the pixel electrode, to stabilize channel regions and enhance on-state current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If time-division control is used to distribute image signals to multiple source wires through a demultiplexer circuit, then the total number of wires connecting the signal supply unit and demultiplexer circuit can be reduced, but the charging and discharging period of each pixel electrode becomes shorter, requiring higher positive bias and causing threshold voltage rise
Solution Approach 1:
The patent applies local quality by differentiating the gate length parameters between pixel TFTs and demultiplexer TFTs. Specifically, the gate length of demultiplexer TFTs (L2) is set to be shorter than that of pixel TFTs (L1), creating localized structural optimization in the demultiplexer circuit region to compensate for threshold voltage rise and maintain on-state current.
Solution Approach 2:
The patent changes physical parameters of the demultiplexer TFTs, specifically reducing the gate length (L2 < L1) and adjusting bias conditions, to counteract the adverse effects of time-division control. This parameter modification enables the demultiplexer TFTs to maintain sufficient on-state current despite the shorter charging/discharging periods imposed by time-division signaling.
2Speed
If higher positive bias is applied to thin-film transistors in the demultiplexer circuit to complete charging and discharging in shorter time, then the switching speed improves, but the threshold voltage rises (positive shift), resulting in decreased on-state current
Solution Approach 1:
The patent implements local quality by creating structurally distinct TFT regions: pixel TFTs with gate length L1 and demultiplexer TFTs with shorter gate length L2. This localized structural differentiation allows demultiplexer TFTs to operate under high-speed switching conditions while maintaining adequate on-state current, without requiring all TFTs in the display to be redesigned.
Solution Approach 2:
The patent applies parameter changes by modifying the gate length parameter specifically for demultiplexer TFTs (L2 < L1). This parameter adjustment, combined with controlled bias conditions, enables the demultiplexer circuit to achieve fast switching speeds while compensating for threshold voltage rise, thereby maintaining reliable on-state current levels.
Data Source
AI summary
A display substrate includes a plurality of first wires; a plurality of second wires; a plurality of first thin-film transistors each connected to any of the plurality of first wires and any of the plurality of second wires; a plurality of pixel electrodes each connected to a corresponding one of the plurality of first thin-film transistors; a signal supply unit that supplies image signals to the plurality of second wires; and a plurality of second thin-film transistors constituting a demultiplexer circuit that distributes, to the plurality of second wires, the image signals supplied from the signal supply unit.