Organic Light Emitting Display Subpixel Structure for Flexible Panels
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Solution Overview
Problem
Conventional organic light emitting displays face issues with high resolution and reliability due to protrusions in the active layer causing electrical shorts and degradation of current when using flexible substrates, which limit the performance and lifespan of the devices.
Innovation Solution
The solution involves forming a storage electrode made of low resistance metal without additional doping below the active layer to maximize the storage capacitor area, preventing electrical shorts and impurity-induced current degradation, while using a dual scan line structure to maintain crystallinity and reduce signal delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser light is radiated onto the amorphous silicon layer to crystallize it into polycrystalline silicon, then the active layer is formed, but protrusions occur at grain boundaries causing electrical shorts and dielectric breakdown
Solution Approach 1:
The patent introduces a buffer layer positioned between the substrate and the amorphous silicon layer, creating an additional dimensional layer to absorb volume expansion during crystallization. This buffer layer acts as a sacrificial element that prevents protrusion formation at grain boundaries while maintaining the polycrystalline silicon structure necessary for transistor operation.
Solution Approach 2:
The buffer layer serves as an intermediary element between the substrate and the active layer. It mediates the volume expansion forces generated during laser crystallization by providing a compliant interface that can accommodate solid-liquid state transitions without transmitting protrusion forces to the gate insulating film.
2Manufacturing precision
If the storage area is formed separately from the channel area through a separate doping process, then the storage capacitor is formed, but high resolution is not achieved
Solution Approach 1:
The patent merges the storage electrode formation with the gate electrode formation processes. The storage electrode is formed simultaneously with the gate electrode using the same doping process and mask alignment, eliminating the need for a separate storage area doping process. This integration maintains high resolution by utilizing the existing precise mask alignment already required for gate electrode formation.
Solution Approach 2:
The gate electrode structure serves dual functions: as the control electrode for the transistor channel and as one plate of the storage capacitor. This multi-functionality eliminates the need for separate storage electrode structures and doping processes, thereby achieving high resolution without increasing fabrication complexity.
3Weight of moving object
If a flexible substrate is used to make the panel thinner, then weight and volume are reduced, but current degradation occurs due to impurities introduced from the substrate
Solution Approach 1:
The buffer layer acts as an intermediary barrier between the flexible substrate and the amorphous silicon layer. It prevents impurities and mobile charges from the flexible substrate from diffusing into the active layer, thereby maintaining current stability while enabling the use of lightweight flexible substrates for thin-panel construction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the resolution and reliability of the organic light emitting display by preventing electrical shorts and impurity-induced current degradation, while reducing the number of masks needed in the fabrication process, thus lowering costs and improving process reliability.
Implementation Method 1
If laser light is radiated onto the amorphous silicon layer, cooling is carried out via momentary dissolution and coagulation processes and thus, polycrystalline silicon cores in a solid state are generated.
Implementation Method 2
cooling is carried out via momentary dissolution and coagulation processes
Implementation Method 3
a growth process in which a solid and liquid interface proceeds in the upward direction and transverse direction of the polycrystalline silicon cores according to a temperature gradient is carried out
Data Source
AI summary
A subpixel structure for a display device and a method of fabricating the display device are discussed. The subpixel structure can include a light emitting diode, a first switching transistor having a first gate electrode and a first active layer, a driving transistor having a second gate electrode and a second active layer, a second switching transistor including a third gate electrode and a third active layer, and at least one of the first, second and third gate electrodes is disposed between the corresponding first, second and third active layers and a substrate.