Row Common Electrode Segmentation for OLED Brightness Uniformity
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Solution Overview
Problem
In organic light emitting displays, process variations in thin-film transistors (TFTs) lead to different threshold voltages, resulting in non-uniform brightness across the display, causing issues like mura (non-uniform brightness) due to inconsistent driving of organic light emitting diodes.
Innovation Solution
The implementation of a method where scan signals and corresponding common voltage signals are sequentially transmitted to rows of pixels, with each row receiving specific scan and common voltage signals to control driving units and reverse bias light emitting devices, ensuring consistent operation and minimizing the impact of TFT threshold voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional driving methods are used with single common electrode, then device complexity is reduced, but brightness uniformity deteriorates due to TFT threshold voltage variations
Solution Approach 1:
The single common electrode is segmented into multiple row common electrodes (first row common electrode, second row common electrode, etc.), with each electrode independently controlling the common voltage for its corresponding row of pixels. This segmentation allows independent optimization of each row's driving conditions, compensating for TFT threshold voltage variations and achieving uniform brightness across the display.
2Illumination intensity
If row-by-row sequential driving is implemented, then brightness uniformity is improved through independent row control, but device complexity increases due to multiple common electrodes and signals
Solution Approach 1:
Each row common electrode serves multiple functions: it provides the common voltage signal for its corresponding row, enables sequential row-by-row driving, and allows independent optimization of each row's operating conditions. This multi-functionality justifies the increased complexity by delivering superior brightness uniformity and display performance.
3Illumination intensity
If multiple row common electrodes are used for sequential transmission, then brightness uniformity is maintained independent of power supply variations, but device complexity and signal transmission requirements increase
Solution Approach 1:
The power supply variation compensation is achieved by segmenting the common electrode into multiple row-specific electrodes. Each row common electrode independently receives and transmits common voltage signals, allowing each row to be driven with optimized voltage levels that compensate for both TFT threshold voltage variations and power supply fluctuations, thereby maintaining uniform brightness.
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 ensures consistent driving currents across pixels, independent of power supply and threshold voltage variations, thereby maintaining uniform brightness and preventing issues like mura, by decoupling driving currents from power supply and threshold voltage variations.
Implementation Method 1
an organic light emitting device has advantages such as spontaneous luminescence
Implementation Method 2
transmitting a plurality of common voltage signals generated in accordance with the scan signals... to reverse bias the light emitting devices
Data Source
AI summary
An organic light emitting display includes scan lines, row common electrodes and rows of pixels. The scan lines sequentially transmit scan signals. The row common electrodes disposed in parallel with the scan lines and sequentially transmit common voltage signals corresponding to the scan signals. The rows of the pixels are electrically coupled to the scan lines and the row common electrodes and sequentially receive the scan signals and the common voltage signals. A method for driving the organic light emitting display is also disclosed herein.