Polycrystalline Silicon TFT Driving Elements for Organic EL Displays
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Solution Overview
Problem
Existing organic electroluminescent (EL) devices face limitations in production yield, resolution, aperture ratio, and brightness due to the use of amorphous silicon thin film transistors, which are prone to deterioration from high current density and have low yield, and top emission types suffer from reduced transmittance and optical efficiency.
Innovation Solution
The use of negative-type polycrystalline silicon thin film transistors as driving elements in a dual plate type organic electroluminescent device, connected in parallel to distribute stress and improve stability, combined with a dual substrate structure to enhance production yield and aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous silicon thin film transistors are used as driving elements, then the device structure is simpler and fabrication is easier, but the production yield is low and the transistors deteriorate from high current density
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to polycrystalline silicon for the driving element transistors. This material parameter change improves production yield and current density handling while maintaining the thin film transistor structure for ease of fabrication.
Solution Approach 2:
The patent segments the transistor array into multiple independent pixel regions with separate driving elements. This segmentation allows parallel processing during fabrication, improving production yield while each individual transistor maintains manageable current density.
2Device complexity
If amorphous silicon thin film transistors are used as driving elements, then the device structure is simpler, but the resolution and aperture ratio are limited
Solution Approach 1:
The patent changes the active layer material from amorphous silicon to polycrystalline silicon, enabling higher resolution displays with improved aperture ratios while maintaining the overall TFT device structure.
3Area of moving object
If top emission type structure is used, then the aperture ratio can be increased, but the transmittance and optical efficiency are reduced
Solution Approach 1:
The patent changes the emission direction parameter from bottom emission to top emission, achieving higher aperture ratios. The use of polycrystalline silicon TFTs with improved characteristics compensates for the optical efficiency trade-off.
4Device complexity
If a single substrate structure is used, then the device is simpler, but the production yield is limited
Solution Approach 1:
The patent segments the device into multiple independent pixel regions on a single substrate, each with its own driving element. This segmentation enables parallel fabrication processing, significantly improving production yield while maintaining single substrate simplicity.
Data Source
AI summary
An organic electroluminescent device includes first and second substrates facing and spaced apart from each other; a gate line on the first substrate; a data line intersecting the gate line to define a pixel region; a switching element connected to the gate line and the data line; an organic electroluminescent diode on the second substrate; and a driving element connected to the switching element and the organic electroluminescent diode, the driving element including a plurality of driving negative-type polycrystalline silicon thin film transistors connected to the organic electroluminescent diode in parallel.