OLED Pixel Driving Circuit Charge Elimination
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Solution Overview
Problem
Organic light emitting diodes (OLEDs) experience reduced luminous efficiency and shortened lifespan due to the accumulation of electrons and holes at interfaces, which creates a built-in electric field hindering recombination and leading to decreased brightness and shorter device life.
Innovation Solution
A pixel driving circuit comprising a switching sub-circuit, a driving sub-circuit, a storage capacitor, a charge eliminating sub-circuit, and a gate voltage resetting sub-circuit, which writes and stores data voltage, reverses the potential between the anode and cathode of the OLED, and resets the gate voltage, respectively, to prevent electron and hole accumulation at interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If OLED operates continuously to emit light, then brightness is maintained, but electrons and holes accumulate at interfaces forming a built-in electric field that reduces luminous efficiency and lifespan
Solution Approach 1:
The patent applies periodic action by implementing a dual scanning signal mechanism: a first scanning signal writes data voltage during the display period to maintain brightness, while a second scanning signal eliminates accumulated charges during the non-display period. This periodic alternation between charge writing and charge elimination prevents interface accumulation, thereby maintaining both brightness and luminous efficiency over time
Solution Approach 2:
The patent implements preliminary action by eliminating accumulated electrons and holes at the interface before they can form a significant built-in electric field that would hinder recombination. The charge elimination operation is performed in advance during the non-display period, preventing the degradation of luminous efficiency before it occurs during the display period
2Illumination intensity
If data voltage is written continuously to maintain display, then brightness is maintained, but charge accumulation at interfaces increases reducing device performance
Solution Approach 1:
The patent converts the harmful effect of charge accumulation into a beneficial process by utilizing the non-display period, when the OLED is not emitting light, to actively eliminate accumulated charges. The second scanning signal is specifically designed to remove excess electrons and holes at the interface, transforming the previously harmful accumulation into a controlled elimination process that improves device performance
3Reliability
If additional scanning signal lines are added to eliminate charges, then charge accumulation is reduced, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by designing the second scanning signal line to serve dual purposes: it controls the elimination of accumulated charges at the OLED interface while also coordinating with the display timing system. This universal approach allows charge elimination to be integrated into the existing scanning architecture without requiring completely separate control lines, thereby reducing the increase in device complexity
Data Source
AI summary
A pixel driving circuit, an organic light emitting display panel and a pixel driving method. The pixel driving circuit includes: a switching sub-circuit, a driving sub-circuit, a storage capacitor and a charge eliminating sub-circuit; the charge eliminating sub-circuit has a control terminal connected to a first scanning signal line, and other terminals connected to the first terminal of the driving sub-circuit, a cathode of the organic light emitting element (OLED) and a reference voltage terminal respectively, and can enable a potential between the anode and the cathode of the organic light emitting element to be reversed under control of the first scanning signal line.