Mixed-Transistor OLED Pixel Circuit for Low Power and Black Luminance
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Solution Overview
Problem
Conventional organic light emitting diode (OLED) displays using low-temperature polycrystalline silicon (LTPS) transistors consume high power due to high turn-off currents, and there is an issue with luminance increase in black images.
Innovation Solution
The use of n-type oxide semiconductor transistors for switching and p-type LTPS transistors for light emission control, along with a compensation transistor to manage threshold voltage, reduces power consumption and prevents luminance increase in black images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If LTPS transistors are used in the circuit portion, then the transistor can be turned on effectively, but the turn-off current becomes excessively high causing high power consumption
Solution Approach 1:
The patent applies different semiconductor material properties to different transistor types within the same pixel circuit. Specifically, n-type oxide semiconductor transistors (with low turn-off current) are used for switching and light emission control, while p-type LTPS transistors (with high mobility) are used for driving. This local differentiation allows each transistor to be optimized for its specific function, resolving the contradiction between power consumption and reliable operation.
2Illumination intensity
If conventional transistors are used, then the circuit can operate, but the black image luminance increases due to insufficient control of turn-off current
Solution Approach 1:
The patent changes the key parameter of semiconductor material type from uniform LTPS to a combination of n-type oxide semiconductor and p-type LTPS. This parameter change fundamentally alters the electrical characteristics, particularly the turn-off current behavior. The n-type oxide semiconductor transistors provide extremely low turn-off current, enabling precise control of pixel current even during off-states, thereby preventing black image luminance increase while maintaining low power consumption.
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 lowers power consumption and improves display quality by accurately rendering black images without unnecessary luminance, enhancing the overall efficiency of the OLED display.
Implementation Method 1
an organic light emitting diode which emits light based on the driving current, the driving current flows through the organic light emitting diode
Data Source
AI summary
An OLED display device includes a pixel having a switching transistor turned on by a scan signal received from a scan line and which transmits a data signal received from a data line to a first node, a driving transistor connected between the first node and a second node and through which a driving current corresponding to the data signal flows, a storage capacitor including one end connected to a power supply and another end connected to a gate electrode of the driving transistor, an OLED emitting light by the driving current, and a light emission control transistor connected between the second node and an anode of the OLED and which is turned on by an light emission control signal and transmits the driving current to the OLED. The switching transistor may be an n-type transistor, and the light emission control transistor is a p-type transistor.