Luminescent Display Pixel Layout With Overlapping TFT Capacitor
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Solution Overview
Problem
Conventional luminescent display devices face design flexibility issues due to the dedicated region required for capacitors, leading to reduced space for other elements and increased current density, which shortens the lifetime of luminescent elements.
Innovation Solution
A luminescent display device is designed where the gate electrode of the thin-film transistor is used as one of the capacitor electrodes, allowing the capacitor to be formed above the transistor and overlapping with it, thereby efficiently using pixel space and enabling the formation of multiple transistors and capacitors in a limited area without a dedicated capacitor region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a dedicated region is allocated for the capacitor in the driving circuit, then the capacitor can be formed with sufficient area, but the region for forming other elements (transistors and luminescent elements) becomes smaller
Solution Approach 1:
The invention merges the capacitor region with the driving circuit region by forming the capacitor above the gate electrode of the thin-film transistor. This integration allows the capacitor to share space with the transistor structure, eliminating the need for a separate dedicated capacitor region and thereby maintaining design flexibility while providing sufficient capacitor area.
Solution Approach 2:
The capacitor is formed in the vertical dimension above the gate electrode rather than in the planar driving circuit region. By utilizing the space above the transistor structure, the invention effectively adds a third dimension to the layout, allowing the capacitor to coexist with the transistor without competing for the same planar space.
2Quantity of substance
If the capacitor area is increased to provide sufficient capacitance, then the capacitance value is adequate, but the region for forming the luminescent element becomes smaller, increasing current density
Solution Approach 1:
The capacitor is integrated above the gate electrode of the driving transistor, merging the capacitor formation space with the transistor structure. This integration ensures that the capacitor achieves adequate capacitance value without encroaching on the luminescent element region, thereby maintaining appropriate current density and extending luminescent element lifetime.
3Ease of manufacture
If a dedicated region is allocated for the capacitor, then the capacitor can be formed independently, but the overall pixel area required increases
Solution Approach 1:
The capacitor is formed above the gate electrode of the thin-film transistor, merging the capacitor region with the driving circuit region. This integration allows the capacitor to be formed independently with adequate area while simultaneously reducing the overall pixel area by eliminating redundant dedicated regions.
Data Source
AI summary
A luminescent display device includes a substrate and a thin-film transistor above the substrate. The thin-film transistor includes a semiconductor layer, a gate insulating film on the semiconductor layer, a gate electrode on the gate insulating film, a source electrode, and a drain electrode. The luminescent display device further includes an interlayer insulating film on the gate electrode, a first capacitor electrode on the interlayer insulating film in a region above the gate electrode, and a luminescent element configured to be driven by a driver to produce luminescence. The driver includes the thin-film transistor, and the first capacitor electrode and the gate electrode constitute a capacitor.