Tunable Current Driver for OLED Display Uniformity
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Solution Overview
Problem
Active-matrix OLED displays face non-uniformity in intensity due to variations in the gate to source voltage of the drive transistor and manufacturing inconsistencies, leading to issues like Mura defects and non-uniform brightness.
Innovation Solution
A tunable current driver comprising a semiconductor memory device with a selective transistor, which adjusts the threshold voltage by using a trapping layer and polysilicon structure to ensure consistent driving current, coupled with an operating method that programs the device to output a predetermined current, thereby maintaining adequate brightness without excessive intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional drive transistor is used in active-matrix OLED displays, then the display can be manufactured with standard processes, but the display intensity becomes non-uniform due to variations in gate to source voltage and manufacturing inconsistencies
Solution Approach 1:
The patent introduces a trapping layer that can store electrical charges, thereby changing the electrical parameters of the drive transistor. By controlling the threshold voltage through charge trapping in the nitrogen oxide layer, the driving current can be precisely adjusted to compensate for manufacturing variations, ensuring uniform display intensity across all pixels.
Solution Approach 2:
The nitrogen oxide trapping layer acts as an intermediary between the gate electrode and the channel, mediating the electrical characteristics of the transistor. This intermediate layer allows for independent control of the threshold voltage without affecting the physical structure or manufacturing process of the underlying transistor.
2Illumination intensity
If the driving current is increased to compensate for low brightness pixels, then brightness uniformity improves, but overall power consumption increases
Solution Approach 1:
The patent applies local quality adjustment by individually tuning the driving current of each pixel through the trapping layer mechanism. Each pixel's threshold voltage can be independently adjusted to achieve uniform brightness, rather than uniformly increasing the current across all pixels, thereby avoiding excessive power consumption while maintaining brightness uniformity.
3Illumination intensity
If the threshold voltage is adjusted to compensate for manufacturing variations, then display uniformity improves, but the device complexity increases due to additional trapping layer and programming requirements
Solution Approach 1:
The patent merges the trapping layer functionality with the existing gate oxide layer structure. The nitrogen oxide layer is integrated into the gate stack as part of the standard transistor fabrication process, combining the threshold voltage adjustment function with the existing device architecture rather than adding completely separate control mechanisms.
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
The solution effectively addresses non-uniformity in display intensity by ensuring consistent driving current, reducing Mura defects and enhancing overall display quality by maintaining adequate brightness across pixels.
Implementation Method 1
The first trapping layer is disposed under the first gate electrode... programming the semiconductor memory device when the driving current is less than a predetermined current
Data Source
AI summary
A tunable current driver comprising a semiconductor memory device and a selective transistor is provided, in which one of the source/drain pair of the semiconductor memory device is electrically coupled with a lighting device, and one of the source/drain pair of the selective transistor is electrically coupled with the gate electrode of the semiconductor memory device. The semiconductor memory device not only acts as “drive transistor” to drive the lighting device, but also is capable of adjusting the threshold voltage thereof.