OLED Array Substrate Grain-Size Tuning for Uniform Pixel Current
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Solution Overview
Problem
Conventional OLED display panels face issues with non-uniformity in threshold voltages of driving transistors due to varying grain sizes of the active medium, leading to inconsistent driving currents and brightness across pixel regions, which affects display performance.
Innovation Solution
The method involves fabricating an array substrate with driving and switching transistors, where the first active medium in the driving transistor has a smaller grain size than the second active medium in the switching transistor, and the transistors are made of polysilicon, with the driving transistor having a thicker gate insulating block to achieve uniform threshold voltages and consistent driving currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the same semiconductor material and formation process are used for both driving transistor and switching transistor, then manufacturing efficiency is improved, but threshold voltage uniformity deteriorates due to varying grain sizes
Solution Approach 1:
The patent applies local quality by differentiating the grain size of the active medium in driving transistors versus switching transistors. Specifically, the driving transistor active medium is formed with a first grain size while the switching transistor active medium has a second grain size different from the first. This local differentiation allows each transistor type to have optimized electrical characteristics suitable for its specific function, thereby achieving uniform threshold voltages across driving transistors while maintaining manufacturing efficiency through a unified formation process.
Solution Approach 2:
The patent implements parameter changes by controlling the grain size parameter of the semiconductor active medium to differ between driving and switching transistors. By adjusting the grain size parameter during the formation process, the patent achieves different electrical properties (threshold voltage characteristics) for each transistor type. This parameter control enables precise tuning of transistor performance without requiring completely separate formation processes, thus resolving the contradiction between manufacturing efficiency and threshold voltage uniformity.
2Adaptability or versatility
If driving transistors have different threshold voltages, then device performance adaptability is improved, but display uniformity deteriorates due to inconsistent driving currents
Solution Approach 1:
The patent applies local quality by creating distinct grain size characteristics in the active medium of driving transistors compared to switching transistors. The driving transistor active medium is specifically engineered with a first grain size that optimizes threshold voltage uniformity across all driving transistors in the array. This localized optimization ensures that all driving transistors provide consistent driving currents to their respective OLEDs, thereby achieving uniform display performance across the entire display panel.
3Device complexity
If the grain size of active medium is not controlled, then manufacturing complexity is reduced, but driving current consistency deteriorates
Solution Approach 1:
The patent implements parameter changes by establishing specific grain size parameters for the active medium during the formation process. By controlling the grain size parameter to differ between driving and switching transistors, the patent achieves consistent driving current output from all driving transistors. This parameter control is integrated into the existing manufacturing process, avoiding excessive complexity while ensuring driving current consistency through precise grain size management.
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 results in uniform driving currents to OLEDs across different pixel regions, enhancing the display performance by ensuring consistent brightness and improving the uniformity of threshold voltages in the OLED display panel.
Implementation Method 1
the first gate insulating block has a greater thickness than a thickness of the second gate insulating block... the non-uniformity of threshold voltages in the driving transistors caused by the non-uniform grain sizes may be smaller
Data Source
Figure 1A~1B
Figure 1C~2
Figure 3
AI summary
An array substrate (100) includes a pixel circuit and a light-emitting diode (02). The pixel circuit includes a driving transistor including a first active medium (A1) made of polysilicon, and a switching transistor including a second active medium (A2) made of polysilicon. The first active medium (A1) has a first grain size. The second active medium (A2) has a second grain size larger than the first grain size. The light-emitting diode (02) is coupled to the pixel circuit.