Dual-Channel Display Transistor Layout for Hysteresis Control
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Solution Overview
Problem
Display devices suffer from hysteresis in the voltage-current characteristic of driving transistors, leading to afterimages on the screen due to varying operating states of the transistors in previous frames.
Innovation Solution
A display device with a dual transistor structure, featuring a first and second driving channel portion, a first and second gate pattern, and a bottom metal layer, which reduces channel length and exposes portions of the active layer to minimize hydrogen ion diffusion and light introduction, thereby improving hysteresis characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the channel length of the driving transistor is reduced, then the hysteresis characteristic is improved, but the driving range and swing width of data voltage are reduced
Solution Approach 1:
The driving transistor is divided into two separate transistors: a first transistor for driving the light-emitting element and a second transistor for generating compensation current. This segmentation allows each transistor to be optimized independently - the first transistor can have shorter channel length for better hysteresis performance while the second transistor maintains the overall driving range and voltage swing capability through its compensation function.
Solution Approach 2:
A compensation transistor is introduced as an intermediary element between the data voltage input and the light-emitting element drive. This compensation transistor generates compensation current that offsets the hysteresis effects in the driving transistor, allowing the driving transistor to operate with optimized short channel length without sacrificing overall driving range and voltage swing width.
2Reliability
If the first gate pattern exposes a portion of the first active layer, then hydrogen ion diffusion is minimized, but the structure becomes more complex
Solution Approach 1:
The first gate pattern is segmented into multiple portions with different exposure characteristics to the first active layer. Some portions expose the active layer to minimize hydrogen ion diffusion, while other portions maintain proper electrical connection. This segmentation allows the structure to achieve hydrogen ion control without requiring complete structural redesign.
Solution Approach 2:
Different portions of the first gate pattern are designed with different local qualities - some areas expose the active layer for hydrogen ion diffusion control, while other areas maintain continuous coverage for electrical functionality. This local differentiation allows the single gate pattern structure to simultaneously achieve both hydrogen ion control and electrical performance without excessive complexity.
Data Source
AI summary
A display device includes: a first active layer disposed on a substrate and including a first driving channel portion and a second driving channel portion which is spaced apart from the first driving channel portion; a first gate pattern disposed on the first active layer, overlapping each of the first driving channel portion and the second driving channel portion in a plan view, and exposing a portion of the first active layer which is disposed between the first driving channel portion and the second driving channel portion; a second gate pattern disposed on the first gate pattern, overlapping the first gate pattern in a plan view, and exposing a portion of the first gate pattern; and a light-emitting element disposed on the second gate pattern.