TFT Threshold Voltage Stabilization via Optical Irradiation
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Solution Overview
Problem
Electroluminescence light emitting display apparatuses face disturbances in image quality due to changes in threshold voltage caused by electrical or thermal stress, which requires a large number of TFTs and capacitors per pixel, hindering resolution improvement.
Innovation Solution
A light emitting display apparatus that irradiates the semiconductor constituting the TFT with light having a wavelength longer than the absorption edge wavelength, using a mechanism such as a light shielding film with a transmissive region or a reflector to selectively filter and direct this light, thereby compensating or suppressing changes in the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large number of TFTs and capacitors are used to compensate threshold voltage changes, then threshold voltage stability is improved, but device complexity increases and resolution improvement is hindered
Solution Approach 1:
The patent extracts the threshold voltage compensation function from complex electrical circuits and transfers it to an optical mechanism. By using a light shielding film with a transmissive region that allows light to reach the semiconductor layer, the system compensates for threshold voltage changes through photo-induced effects rather than electrical feedback circuits, thereby reducing device complexity while maintaining reliability
Solution Approach 2:
The patent replaces the electrical compensation system (TFTs and capacitors) with an optical system (light shielding film with transmissive region). Light with wavelength longer than the absorption edge wavelength of the semiconductor is transmitted to induce photo-excitation, which compensates for threshold voltage shifts caused by electrical or thermal stress, thereby substituting complex electrical compensation with a simpler optical mechanism
2Reliability
If light shielding film with transmissive region is used to irradiate semiconductor, then threshold voltage stability is improved, but device structure becomes more complex
Solution Approach 1:
The light shielding film serves multiple functions: it blocks harmful light from reaching the semiconductor while containing a transmissive region that allows compensating light to pass through. This multi-functional design integrates light shielding and light transmission control in a single component, minimizing additional structural complexity while achieving threshold voltage stabilization
Solution Approach 2:
The light shielding film has non-uniform properties with most regions being light-blocking while specific local regions (transmissive regions) allow light transmission. This local quality differentiation enables precise control of light exposure to the semiconductor, providing threshold voltage compensation only where needed without compromising the overall light shielding function
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 effectively stabilizes the threshold voltage of the driving TFT, maintaining image quality and allowing for higher display resolution by reducing the need for extensive compensating circuits.
Implementation Method 1
irradiating the semiconductor constituting the TFT with at least a part of light whose wavelength is longer than a predetermined wavelength among the light emitted by the light emitting element
Data Source
AI summary
There is provided a light emitting display apparatus including at least a light emitting element and a thin film transistor (TFT) for driving the light emitting element, characterized in that a mechanism is provided in which a semiconductor constituting the TFT is irradiated with at least a part of light whose wavelength is longer than a predetermined wavelength among the light emitted by the light emitting element.