Series-Connected OLED Pixel Structure for Current Stability
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Solution Overview
Problem
Conventional organic electroluminescent display panels using amorphous Si TFTs face issues with unstable current and increased power consumption due to the placement of luminescent devices, affecting panel uniformity and the lifetime of the display.
Innovation Solution
A pixel structure with multiple luminescent devices connected in series, where each device is positioned between the source electrode of the thin film transistor and the voltage source, reducing the driving current and thermal energy, and utilizing a partitioned substrate to form sub-pixel regions with series-connected electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single luminescent device is used in each pixel, then the structure is simple, but the driving current is large causing unstable TFT operation and high power consumption
Solution Approach 1:
The patent divides a single luminescent device into multiple luminescent devices connected in series within each pixel. This segmentation reduces the driving current through each individual device while maintaining the overall luminescence output, thereby stabilizing TFT operation and reducing power consumption.
Solution Approach 2:
The patent introduces series connection configuration as an intermediary mechanism between the TFT and the luminescent devices. By placing multiple luminescent devices in series, the current is reduced and the voltage is distributed across multiple devices, stabilizing the TFT operating conditions.
2Ease of manufacture
If a single luminescent device is used in each pixel, then the manufacturing process is simple, but the power consumption is high and thermal energy is excessive
Solution Approach 1:
The patent segments the luminescent function across multiple devices in series, which reduces the current and power consumption of each individual device while maintaining the overall brightness. This approach is compatible with existing manufacturing processes.
Solution Approach 2:
The patent changes the electrical parameters of the pixel by configuring multiple luminescent devices in series, thereby reducing the driving current and power consumption while maintaining the luminescence output through adjusted voltage distribution.
3Device complexity
If luminescent device is placed between TFT and voltage source, then the connection is simple, but the threshold voltage of TFT is affected and current becomes unstable
Solution Approach 1:
The patent segments the voltage drop across multiple luminescent devices in series, which reduces the voltage impact on the TFT threshold voltage and stabilizes the current flow through the pixel circuit.
4Illumination intensity
If large driving current is used, then the luminescence output is sufficient, but the lifetime of luminescent device is reduced due to thermal energy
Solution Approach 1:
The patent divides the luminescence function across multiple devices in series, reducing the current and thermal load on each device while maintaining the overall luminescence output, thereby extending device lifetime.
Solution Approach 2:
The patent converts the harmful effect of high current and thermal energy into a beneficial configuration by using series connection, where the voltage is distributed across multiple devices, reducing thermal stress on each individual device while maintaining sufficient luminescence output.
Data Source
AI summary
A pixel structure of an organic electroluminescent display panel has a plurality of sub-pixel regions. Each of the sub-pixel regions has a plurality of organic luminescent devices electrically connected in series, and the organic luminescent devices disposed in a same sub-pixel region are disposed between a source electrode of a thin film transistor and a voltage source Vdd.