Auxiliary Electrode Shields OLED Channel From Cathode Field Effect
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Solution Overview
Problem
In organic light emitting devices (OLEDs), the continuous increase of output current due to the field effect generated by the cathode connected to the drain electrode of the driving thin film transistor leads to non-uniform brightness and image quality deterioration, particularly in top emission OLEDs where the aperture ratio is critical for high resolution and product life.
Innovation Solution
Incorporating an auxiliary electrode electrically coupled to the ground line and source electrode of the driver transistor, which is positioned between the light emitting diode and the channel region to shield the channel from the electric field generated by the light emitting diode, thereby blocking the field effect and maintaining a stable source potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the first electrode (cathode) is formed on the driving thin film transistor to improve aperture ratio, then the aperture ratio is improved, but the field effect generates continuous increase of output current leading to non-uniform brightness and image quality deterioration
Solution Approach 1:
An auxiliary electrode is introduced as an intermediary component between the cathode (first electrode) and the channel region of the driving thin film transistor. This auxiliary electrode is electrically connected to the source electrode and positioned to shield the channel from the electric field generated by the cathode, thereby preventing the field effect that causes continuous current increase while maintaining the high aperture ratio design
2Productivity
If the cathode voltage changes due to drain electrode voltage changes, then the field effect increases current through the channel, but this prevents output current saturation and causes brightness non-uniformity
Solution Approach 1:
The auxiliary electrode is configured to preemptively counteract the harmful field effect before it can cause continuous current increase. By being electrically connected to the source electrode and positioned between the cathode and channel, it creates a shielding effect that prevents the cathode's electric field from affecting the channel, thereby maintaining output current saturation characteristics
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 configuration prevents output current saturation, improves image quality by maintaining consistent brightness, and enhances the reliability and lifespan of the OLED by reducing brightness reduction and non-uniformity issues.
Implementation Method 1
an auxiliary electrode is electrically coupled to the ground line and to the source electrode of the driver transistor. The auxiliary electrode resides between the light emitting diode and the channel region of the driver transistor and is configured to shield the channel region of the driver transistor from an electric field generated by the light emitting diode
Implementation Method 2
The OLED uses a phenomenon that an electron and a hole form an electron-hole pair in a semiconductor, or carriers are excited to a higher energy state and then fall down to a ground state, which is a stable state, and emit light
Data Source
AI summary
A top emission OLED includes a driving TFT including a channel region and source and drain electrodes. A power supply, a ground line, and a light emitting diode are electrically coupled to the TFT and an auxiliary electrode is electrically coupled to the ground line and to the source electrode of the driver transistor. The auxiliary electrode resides between the light emitting diode and the channel region of the driver transistor and is configured to shield the channel region of the driver transistor from an electric field generated by the light emitting diode.