OLED Pixel Circuit Alternating Current Driving to Prevent Ion Polarization
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Solution Overview
Problem
The long-term DC driving voltage in active matrix OLEDs leads to ion polarization, increasing the threshold voltage and reducing light-emitting efficiency and lifespan, especially in large and high-intensity displays.
Innovation Solution
A pixel circuit with a charging sub-circuit, a capacitor, and two driving sub-circuits (one n-type and one p-type) that drive light emitting devices in opposite directions, allowing them to emit light alternately, thereby reducing the impact of DC voltage on OLEDs and extending their lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If DC driving voltage is applied to OLED for long-term display, then the light emitting device can maintain stable light emission, but ion polarization occurs inside the OLED which increases threshold voltage and reduces light-emitting efficiency and lifespan
Solution Approach 1:
The patent applies periodic AC driving voltage instead of continuous DC voltage to the OLED. By alternating the voltage polarity periodically, the patent prevents ion polarization accumulation that occurs with DC driving, thereby maintaining light-emitting efficiency while enabling long-term stable operation. The periodic reversal of voltage direction prevents ions from accumulating in one position, solving the contradiction between lifespan and efficiency.
Solution Approach 2:
The patent changes the electrical parameter from DC voltage to AC voltage with specific frequency and amplitude characteristics. This parameter change transforms the driving mode to prevent ion polarization while maintaining adequate light emission. The AC voltage parameters are optimized to ensure the OLED operates reliably without suffering from DC-induced threshold voltage shifts.
2Ease of manufacture
If DC driving is used to simplify the pixel circuit structure, then manufacturing and operation become easier, but the threshold voltage increases and light-emitting efficiency decreases
Solution Approach 1:
The patent implements AC driving with periodic voltage reversal to prevent ion polarization. This approach maintains a relatively simple pixel circuit structure while improving light-emitting efficiency by eliminating the threshold voltage increase problem associated with DC driving. The periodic action is achieved through circuit design that enables voltage polarity switching without requiring excessively complex additional components.
3Illumination intensity
If high intensity display is implemented to improve brightness, then the display performance is enhanced, but the ion polarization effect is amplified which shortens the OLED lifespan
Solution Approach 1:
The patent uses AC driving with periodic voltage reversal to counteract the intensified ion polarization effect that occurs during high-intensity display. By alternating the voltage direction, the patent prevents permanent ion accumulation even under high current conditions, thereby maintaining brightness performance while extending the lifespan of the OLED in high-intensity applications.
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 solution effectively doubles the lifespan of light emitting devices by alternating the driving current direction, reducing the adverse effects of DC voltage on OLEDs and improving light-emitting efficiency and display uniformity.
Implementation Method 1
a capacitor C1, and a switching transistor T2. A first terminal of the capacitor C1 is connected to the gate of the driving transistor T1
Implementation Method 2
The Organic Light Emitting Diode (OLED) is a light emitting device that is used commonly in the organic light-emitting field
Data Source
AI summary
A pixel circuit and a method for driving the same, a display panel and a display apparatus are configured to improve the lifespan of the pixel circuit. The pixel circuit comprises: a charging sub-circuit (1), a capacitor (CST), a first driving sub-circuit (2) and a second driving sub-circuit (3); a first terminal of the capacitor (CST) is connected to a first terminal of the first driving sub-circuit (2) and a first terminal of the second driving sub-circuit (3), and a second terminal of the capacitor (CST) is connected to the charging sub-circuit (1); a second terminal of the first driving sub-circuit (2) is connected to a first light emitting device (D1), a second terminal of the second driving sub-circuit (3) is connected to a second light emitting device (D2), wherein a driving current (I1) flowing from the first driving sub-circuit (2) to the first light emitting device (D1) is in an opposite direction to a driving current (I2) flowing from the second driving sub-circuit (3) to the second light emitting device (D2); the charging sub-circuit (1) is configured to charge the capacitor (CST), and when the capacitor (CST) is discharged, the first driving sub-circuit (2) drives the first light emitting device (D1) to emit light or the second driving sub-circuit (3) drives the second light emitting device (D2) to emit light.