OLED Anode Positioning to Reduce Parasitic Capacitance
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Solution Overview
Problem
Organic light emitting diodes (OLEDs) in display devices face issues with leakage current and kickback voltage, leading to unwanted light emission during black data signals and interference with data signals due to parasitic capacitance, which affects contrast and power consumption.
Innovation Solution
The design includes a display panel with pixel circuits where the first parasitic capacitance between the emission unit and the pixel driving unit is minimized by positioning the anode electrode of one pixel circuit over the pixel driving unit of an adjacent pixel circuit, and using transistors and capacitors to control the electrical connection and bias voltage, ensuring the OLED does not emit light during black data signals and minimizing kickback voltage without additional scan signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the anode electrode is positioned within the same pixel circuit, then the parasitic capacitance is larger, but this causes kickback voltage to affect the data signal
Solution Approach 1:
The anode electrode of the OLED is extracted from the same pixel circuit and repositioned to overlap with the pixel driving unit of an adjacent pixel circuit. This spatial extraction reduces the parasitic capacitance between the emission unit and its own pixel driving unit, thereby minimizing kickback voltage interference with the data signal while maintaining electrical connectivity through the switch unit.
Solution Approach 2:
The switch unit acts as an intermediary between the emission unit and the pixel driving unit. It controls the electrical connection timing, allowing the OLED to be electrically isolated from the pixel driving unit during periods when voltage changes occur, thereby preventing kickback voltage from coupling into the data signal line while still enabling normal operation during active periods.
2Object-affected harmful factors
If the parasitic capacitance is reduced by repositioning the anode electrode, then kickback voltage is minimized, but the manufacturing precision is increased
Solution Approach 1:
The solution moves the anode electrode positioning problem from the planar two-dimensional layout to a three-dimensional overlapping configuration. By allowing the anode electrode to extend into the spatial region above the adjacent pixel circuit's pixel driving unit, the design achieves reduced parasitic capacitance without requiring complex lateral routing, thus managing the manufacturing precision challenge through vertical spatial utilization.
3Ease of operation
If additional scan signals are used to control the switch unit, then the electrical connection can be precisely controlled, but the device complexity increases
Solution Approach 1:
The switch unit is designed to be controlled by existing control signals (scan signals and emission signals) that are already present in the OLED display system. By making the switch unit responsive to these existing multi-purpose signals, the design achieves precise electrical connection control without requiring additional dedicated control signal lines, thus avoiding increased device complexity.
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 improves contrast, enables high-resolution display, and optimizes power consumption by preventing unwanted light emission and kickback voltage interference, enhancing the overall performance of OLED display devices.
Implementation Method 1
an organic light emitting diode that is a self-light-emitting device
Implementation Method 2
a first capacitor having a first electrode coupled to the first electrode of the organic light emitting diode, and a second electrode coupled to the second electrode of the organic light emitting diode
Data Source
AI summary
A display panel includes a plurality of pixel circuits. Each of pixel circuits comprises an emission unit including an organic light emitting diode, a pixel driving unit configured to drive an emission unit based on a scan signal and a data signal, and a switch unit configured to control an electrical connection between an emission unit and a pixel driving unit based on an emission signal. A first parasitic capacitance between an emission unit included in a first pixel circuit of pixel circuits and a pixel driving unit included in a first pixel circuit is smaller than a second parasitic capacitance between an emission unit included in a first pixel circuit and a pixel driving unit included in a second pixel circuit of pixel circuits adjacent to a first pixel circuit.