OLED Pixel Inverse Voltage Transistor Leakage Current
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Solution Overview
Problem
In organic light emitting diode (OLED) display devices, the leakage current flowing when the driving transistor is off reduces the lifespan of the OLED and can cause undesired light emission, leading to a deteriorated contrast ratio due to the anode floating and potential light emission.
Innovation Solution
Incorporating an inverse voltage transistor between the anode of the OLED and a reverse bias power source, which applies an inverse voltage during the turn-off period of the driving transistor, preventing leakage current and ensuring the OLED is completely turned off, thus enhancing its lifespan and maintaining contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driving transistor is turned off to control the OLED, then the OLED should be completely turned off to maintain contrast ratio, but the anode of the OLED floats and leakage current flows which reduces the lifespan of the OLED
Solution Approach 1:
An inverse voltage transistor is introduced as an intermediary component between the driving transistor and the OLED anode. This transistor acts as a mediator that actively pulls the anode to a fixed potential when the driving transistor is off, preventing both floating and leakage current without requiring additional complex circuitry.
Solution Approach 2:
The harmful floating potential and leakage current are extracted from the system by introducing the inverse voltage transistor that provides a dedicated path to ground for the anode. This separates the function of current control (driving transistor) from the function of potential stabilization (inverse voltage transistor), eliminating the harmful effects.
2Illumination intensity
If the driving transistor is turned off to stop light emission, then contrast ratio improves, but undesired light emission occurs due to leakage current which deteriorates contrast ratio
Solution Approach 1:
The inverse voltage transistor serves as a mediator that prevents leakage current from reaching the OLED anode. By actively pulling the anode to ground potential, it ensures complete turn-off of the OLED and eliminates undesired light emission, thereby maintaining high contrast ratio.
3Device complexity
If no inverse voltage transistor is used, then device complexity is low, but the anode floats and leakage current reduces OLED lifespan
Solution Approach 1:
The solution extracts only the essential function needed to prevent floating and leakage current - a single transistor dedicated to pulling the anode to ground. This minimal addition (one transistor) provides significant reliability improvement without requiring complex multi-transistor circuits or additional components.
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 implementation of the inverse voltage transistor effectively prevents leakage current and maintains the OLED in an off state, improving its lifespan and contrast ratio by ensuring no unwanted light emission occurs when the driving transistor is off.
Implementation Method 1
an inverse voltage transistor positioned between an anode of the organic light emitting diode (OLED) and a reverse bias power source. The inverse voltage transistor includes a gate electrode connected to one of a first electrode and a second electrode, and is configured to transmit an inverse voltage to the organic light emitting diode (OLED) during a turn-off period of the driving transistor
Data Source
AI summary
A pixel and an organic light emitting diode (OLED) display device including the same are disclosed. The pixel includes an organic light emitting diode and an inverse voltage transistor positioned between an anode of the organic light emitting diode and a reverse bias power source, and configured to transmit the inverse voltage to the organic light emitting diode (OLED).