TFT Reset Voltage Strategy for OLED Threshold Recovery
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Solution Overview
Problem
The increasing threshold voltage in amorphous silicon thin film transistor (a-Si TFT) based OLED panels reduces electric current, leading to decreased illumination and shorter panel life, as electrons are trapped in the gate dielectric, and existing reset methods require high voltages that reduce operation efficiency.
Innovation Solution
A method that adjusts the electricity of the TFT by applying a gate resetting voltage smaller than or equal to the source or drain resetting voltage, using a driving chip to control the sequence, with the source and drain electrodes receiving positive resetting voltages and the gate electrode receiving a negative resetting voltage, generating a sufficient potential difference to release trapped electrons without high absolute voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high positive voltage or negative voltage is applied to the gate dielectric to release trapped electrons, then the threshold voltage is recovered, but the operation efficiency of the OLED is reduced
Solution Approach 1:
The patent applies a reverse bias voltage across the gate dielectric layer by setting the gate electrode to 0V and the source/drain electrodes to positive voltage (e.g., +15V), creating an electric field that extracts trapped electrons without requiring high absolute voltage levels on the gate dielectric, thus maintaining OLED operation efficiency while recovering threshold voltage
Solution Approach 2:
The patent uses the source/drain electrodes as intermediary elements to generate the electric field across the gate dielectric, rather than directly applying high voltage to the gate dielectric. This intermediary approach allows electron release through the channel while avoiding direct high voltage stress on the OLED structure
2Reliability
If greater positive voltage is applied to the source/drain electrode to form electric field for releasing electrons, then the threshold voltage recovers, but the voltage level increases power consumption
Solution Approach 1:
The patent optimizes the voltage parameters by applying moderate positive voltage (e.g., +15V) to the source/drain electrodes during reset period, which is sufficient to create the necessary electric field for electron extraction without excessive voltage that would increase power consumption. The voltage is applied only during the reset period rather than continuously
3Reliability
If high voltage is applied to reset the TFT electricity, then the trapped electrons are released, but the absolute voltage level reduces operation efficiency
Solution Approach 1:
The patent changes the voltage application strategy by using moderate voltage levels (+15V to -15V range) applied to the source/drain electrodes during reset periods, rather than high absolute voltage on the gate dielectric. This creates sufficient potential difference for electron release while maintaining energy efficiency during normal operation
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 approach reduces power consumption and increases power efficiency by generating a potential difference of about 30 volts with voltages between -15 and +15 volts, improving the reset process for OLED panels.
Implementation Method 1
the electrons are easily trapped in the gate dielectric to raise the threshold voltage of the a-Si TFT
Implementation Method 2
apply an electric field from the source/drain electrode of the TFT toward the gate electrode for driving the electrons away from the gate dielectric
Data Source
AI summary
A method for adjusting the electricity of a TFT has the steps of starting a displaying sequence by driving the TFT and resetting the electricity of the TFT. The step of starting the display sequence by driving the TFT further comprises the steps of: (a) providing a gate driving voltage to the gate electrode of the TFT; (b) providing a source driving voltage to the source electrode of the TFT; and (c) providing a drain driving voltage to the drain electrode of the TFT. The step of resetting the electricity of the TFT comprises the steps of: (a) providing a gate resetting voltage to the gate electrode of the TFT; (b) providing a source resetting voltage to the source electrode of the TFT; and (c) providing a drain resetting voltage to the drain electrode of the TFT. The gate resetting voltage is smaller than or equal to the source resetting voltage or the drain resetting voltage. The source resetting voltage and the drain resetting voltage are adjustable.