OLED Pixel Circuit Leakage Current Reduction via Transistor Segmentation
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in reducing leakage current and flicker recognition, particularly in high-frequency driving, due to limitations in transistor design and data signal transmission.
Innovation Solution
The display device incorporates a pixel structure with PMOS and NMOS transistors, including a compensating transistor and an initialization transistor, connected in a specific configuration to manage data signals and reduce current leakage, using oxide semiconductor layers for improved turn-off characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional transistor design is used in organic light emitting display devices, then device complexity is reduced, but leakage current increases and flicker recognition occurs in high-frequency driving
Solution Approach 1:
The pixel circuit is divided into multiple functional transistor units: a first transistor for driving current control, a second transistor for data signal transmission, a third transistor for threshold voltage compensation, and a fourth transistor for initialization. This segmentation allows each transistor to perform a specific function, reducing overall leakage current while managing complexity through functional specialization.
Solution Approach 2:
The fourth transistor performs preliminary initialization of the gate electrode voltage before the pixel operates, and the third transistor provides preliminary compensation for threshold voltage deviations. These preliminary actions prevent leakage current accumulation and flicker before they occur during high-frequency driving.
2Productivity
If high-frequency driving is implemented, then productivity is improved, but leakage current increases and flicker recognition occurs
Solution Approach 1:
The third transistor creates a feedback mechanism by transmitting the data signal with compensated threshold voltage to the gate electrode of the first transistor. This feedback loop continuously corrects for threshold voltage deviations that occur during high-frequency driving, preventing flicker recognition and maintaining reliable operation at high productivity levels.
3Reliability
If PMOS transistors are used for first and second transistors, then turn-off characteristics are improved, but manufacturing complexity increases due to multiple semiconductor layers
Solution Approach 1:
Different semiconductor layers are used in different regions of the pixel circuit: the lower semiconductor layer forms PMOS transistors (first and second transistors) where superior turn-off characteristics are critical, while the upper semiconductor layer forms NMOS transistors (third and fourth transistors) where different electrical characteristics are needed. This local quality differentiation optimizes performance in critical regions while managing manufacturing complexity through spatial separation of transistor types.
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 effectively reduces current leakage and prevents flicker recognition, ensuring reliable image display even in high-frequency driving by providing compensation time for threshold voltage deviations.
Implementation Method 1
an organic light emitting display device displays an image by using an organic light emitting diode which generates light by recombination of electrons and holes
Data Source
AI summary
A display device includes a plurality of pixels arranged in a first direction; a first data line extending along a first edge of the pixel row; a second data line extending along a second edge of the pixel row; a first pixel connected to the first data line; and a second pixel adjacent to the first pixel and connected to the second data line. Each of the first and second pixels includes a light emitting diode, a first transistor to transmit a driving current to the light emitting diode, a second transistor to transmit a data signal to the first transistor, a third transistor to transmit the data signal having a compensated threshold voltage to the first transistor, and a fourth transistor to transmit an initialization voltage signal to the first transistor. The first and second transistors are PMOS transistors. The third and fourth transistors are NMOS transistors.