OLED Driving Transistor Bottom-Gate Layout for Afterimage Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic light emitting diode displays face challenges with protrusions in polycrystalline semiconductor layers, leading to increased thickness and potential for instantaneous afterimages due to the impact on gate insulating layers and transistor characteristics.
Innovation Solution
The use of a bottom gate structure for the driving transistor, where the gate electrode is disposed under the polycrystalline semiconductor layer, reduces the thickness of the gate insulating layer and minimizes the influence of protrusions, while top gate structures are used for other transistors to maintain display quality without significant current provision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a top gate structure is used for the driving transistor, then the manufacturing process is simpler, but the protrusions in the polycrystalline semiconductor layer increase the thickness and cause instantaneous afterimages
Solution Approach 1:
The patent inverts the conventional top gate structure to a bottom gate structure for the driving transistor. The gate electrode is positioned beneath the polycrystalline semiconductor layer instead of above it, which eliminates the problem of protrusions increasing thickness and causing afterimages while maintaining manufacturing feasibility
Solution Approach 2:
The patent applies different gate structures to different transistors in the pixel circuit. The driving transistor uses a bottom gate structure to eliminate afterimages, while other transistors (switching, compensation) use conventional top gate structures, optimizing each transistor's function for its specific role
2Length of stationary object
If the gate insulating layer thickness is increased to accommodate protrusions, then the display device thickness increases, but if it is decreased, the transistor characteristics are affected
Solution Approach 1:
By inverting the gate structure to bottom gate, the patent eliminates the need to increase gate insulating layer thickness to accommodate protrusions. The gate electrode is positioned where it does not interfere with the protrusions, allowing the use of thinner gate insulating layers while maintaining transistor reliability
3Length of stationary object
If protrusions are present in the polycrystalline semiconductor layer, then the display device thickness increases, but removing them affects manufacturing process
Solution Approach 1:
Instead of trying to remove or prevent protrusions in the polycrystalline semiconductor layer, the patent accepts them as an inevitable byproduct of the manufacturing process and designs the bottom gate structure to work around them. This converts the harmful effect of protrusions into a manageable design consideration
Solution Approach 2:
The bottom gate structure positions the gate electrode beneath the semiconductor layer, where it is not affected by surface protrusions. This inversion allows the manufacturing process to proceed without special measures to eliminate protrusions while still achieving thin display device construction
Data Source
AI summary
An organic light emitting diode display includes a driving transistor and a compensation transistor. The driving transistor includes a first gate electrode disposed on a substrate, a polycrystalline semiconductor layer disposed on the first gate electrode of the driving transistor and including a first electrode, a second electrode, and a channel, and a second gate electrode disposed on the polycrystalline semiconductor layer of the driving transistor. The compensation transistor includes a polycrystalline semiconductor layer including a first electrode, a second electrode, and a channel, and a gate electrode disposed on the polycrystalline semiconductor layer of the compensation transistor.