OLED Pixel Circuit Polarity Inversion for Image Sticking
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Solution Overview
Problem
Organic light emitting displays (OLEDs) face efficiency degradation and image sticking issues due to prolonged voltage imbalances between anode and cathode electrodes, leading to reduced lifespan and image retention problems.
Innovation Solution
The implementation of a pixel circuit design that includes specific switch configurations and capacitors to manage voltage levels, compensate for threshold voltages, and increase current supply to the OLED, thereby mitigating efficiency losses and image sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional OLED structure with anode and cathode electrodes is used, then light emission is achieved through electron-hole recombination, but efficiency degradation and image sticking occur due to voltage imbalance and carrier accumulation over time
Solution Approach 1:
The patent applies inversion by reversing the voltage polarity periodically. Instead of maintaining a fixed voltage polarity with the anode always positive and cathode always negative, the invention switches the polarity so that the anode becomes negative and cathode becomes positive during alternating periods. This inversion prevents carrier accumulation at the electrodes by periodically reversing the electric field direction, thereby eliminating image sticking and efficiency degradation while maintaining reliable OLED operation
Solution Approach 2:
The patent implements periodic action by alternating the voltage polarity between two states over time. A control circuit generates alternating control signals that switch the OLED between a first state (anode positive, cathode negative) and a second state (anode negative, cathode positive). This periodic reversal of voltage polarity prevents permanent carrier accumulation at electrode interfaces,解决了 the reliability and efficiency degradation problems associated with continuous unidirectional current flow
2Ease of operation
If prolonged voltage is applied to maintain image display, then image sticking occurs due to carrier accumulation at electrodes, but reducing voltage affects display brightness and quality
Solution Approach 1:
The patent uses periodic action by alternating the OLED between two voltage polarity states. During each period, the OLED displays an image with normal brightness using conventional polarity, then switches to reversed polarity where the same image data is applied but with inverted electrode polarities. This periodic reversal prevents carrier accumulation that causes image sticking while maintaining display quality during the active display phases
Solution Approach 2:
The patent applies inversion by reversing the voltage polarity during alternating periods. When the OLED would normally operate with anode positive and cathode negative, the invention periodically switches to anode negative and cathode positive. This inversion clears accumulated carriers from electrode interfaces, preventing image sticking artifacts while maintaining ease of operation and display quality during the active display periods
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 effectively suppresses image sticking and extends the lifespan of OLEDs by dynamically adjusting current supply in response to efficiency degradation, ensuring consistent performance and longevity.
Implementation Method 1
at the EML, the electron(s) supplied from the ETL and the hole(s) supplied from the HTL may recombine with each other, thereby generating a predetermined amount of light
Implementation Method 2
an organic light emitting display is a display that emits light by electrically exciting a fluorescent or phosphorescent compound
Data Source
AI summary
An organic light emitting display, including a driving transistor electrically coupled to a first power line, a first switch electrically coupled to the driving transistor and an emission line, a second switch electrically coupled to the driving transistor and a previous scan line, a third switch electrically coupled to the first switch and a data line, a fourth switch electrically coupled to the data line and the third switch, a fifth switch electrically coupled to the driving transistor and a scan line, a first capacitor electrically coupled to the second switch and the third switch, a second capacitor electrically coupled to the third switch and the fifth switch, and an organic light emitting diode electrically coupled to the driving transistor and a second power line.