Light-Emitting Pixel Array with Bypass Capacitor Stripe Suppression
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Solution Overview
Problem
Fluctuations in power supply voltage cause horizontal stripes in the display of light emitting devices due to parasitic capacitances, leading to uneven luminance in the display.
Innovation Solution
Strengthen the capacitive coupling between the power supply wiring and the cathode electrode by incorporating bypass capacitors with various structures, such as MIM, MOS, and MOM, to synchronize the cathode voltage with power supply voltage fluctuations, thereby maintaining consistent gate-source voltage of the driving transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power supply wiring is used to supply power to the driving transistor, then the light emitting element can be driven, but fluctuations in power supply voltage cause horizontal stripes in the display due to parasitic capacitances
Solution Approach 1:
A bypass capacitor is introduced as an intermediary component between the power supply wiring and the cathode electrode. This capacitor acts as a mediator that couples the power supply voltage fluctuations to the cathode electrode, ensuring that the cathode voltage follows the power supply voltage changes and thereby maintaining stable gate-source voltage in the driving transistor, which prevents horizontal stripes in the display
Solution Approach 2:
The bypass capacitor creates a feedback mechanism where the cathode voltage is continuously adjusted to follow the power supply voltage fluctuations. This feedback ensures that any changes in power supply voltage are automatically reflected in the cathode voltage, maintaining consistent operating conditions for the light emitting element and preventing display artifacts
2Reliability
If bypass capacitor is added to suppress power supply voltage fluctuations, then horizontal stripes are prevented, but device structure becomes more complex
Solution Approach 1:
The bypass capacitor is nested within the existing pixel structure, specifically positioned in the capacitance portion below the bottom surface of the first electrode layer. The capacitor utilizes the existing layer structure by placing its first electrode in the fourth electrode layer and second electrode in the fifth electrode layer, effectively integrating the capacitor functionality into the current device architecture without adding external complexity
Solution Approach 2:
The capacitance portion serves multiple functions: it acts as a bypass capacitor to suppress power supply voltage fluctuations, provides electrical connection between the power supply wiring and cathode electrode, and is integrated into the existing pixel structure. This multi-functionality reduces the need for separate dedicated capacitor structures, thereby limiting the increase in 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
The capacitive coupling effectively suppresses the influence of power supply voltage fluctuations, preventing horizontal stripes and ensuring uniform luminance across the display.
Implementation Method 1
a capacitance portion including a first electrode and a second electrode. The first electrode is electrically connected to the power supply wiring, and the second electrode is electrically connected to the second electrode layer
Data Source
AI summary
A light emitting device comprises a substrate that includes a light emitting pixel array including a plurality of light emitting pixels each including a light emitting element and a driving transistor configured to drive the light emitting element, a power supply wiring configured to supply a power supply voltage to the driving transistor, and a capacitance portion including a first electrode and a second electrode. The light emitting element includes a first electrode layer, a light emitting layer arranged on the first electrode layer, and a second electrode layer arranged on the light emitting layer. The first electrode and the second electrode are located at positions lower than a bottom surface of the first electrode layer, the first electrode is electrically connected to the power supply wiring, and the second electrode is electrically connected to the second electrode layer.