Display Pixel Transistor Oxide Channel Leakage Current Reduction
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Solution Overview
Problem
Display devices face issues with leakage current in photoelectric conversion elements, which deteriorate their performance and reduce the photocurrent generated upon exposure to external light.
Innovation Solution
A display device design that includes a pixel with a driving transistor, a first transistor with an oxide semiconductor channel, and an optical sensor with sensing transistors, where the first transistor applies an initialization voltage to the light-emitting element and controls the connection between the light-emitting element and the driving transistor, reducing leakage current and increasing photocurrent by managing voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a photoelectric conversion element is used in a display device, then touch recognition and fingerprint recognition functions are enabled, but leakage current deteriorates the performance of the photoelectric conversion element
Solution Approach 1:
The pixel is divided into two independent functional units: a display driver for the light-emitting element and an optical sensor with its own sensing driver for the photoelectric conversion element. This segmentation allows the optical sensor to operate independently with dedicated control circuits, enabling the photoelectric conversion element to function optimally for sensing while the display driver manages the light-emitting element separately, thus preventing interference and performance deterioration
Solution Approach 2:
The sensing driver acts as an intermediary between the photoelectric conversion element and the read-out line. It includes a first sensing transistor that controls the sensing current flowing into the read-out line based on the voltage of the sensing anode, and a reset transistor that initializes the sensing anode to a first-level voltage. This intermediary structure isolates the photoelectric conversion element from direct connection to the read-out line, preventing leakage current from affecting its performance while enabling proper signal readout
2Power
If the photoelectric conversion element is exposed to external light, then photocurrent is generated, but leakage current reduces the amount of photocurrent
Solution Approach 1:
The reset transistor performs preliminary action by initializing the sensing anode of the photoelectric conversion element to a first-level voltage before the sensing operation begins. This preliminary initialization ensures that the photoelectric conversion element starts from a known voltage state, preventing accumulation of leakage current that would otherwise reduce the photocurrent signal. The emission control signal controls the first transistor to apply initialization voltage to the light-emitting element anode, and similarly controls the reset transistor to initialize the sensing anode, ensuring both elements are properly prepared before operation
Solution Approach 2:
The invention changes the voltage parameter of the sensing anode through the reset transistor, which initializes it to a first-level voltage that is lower than the common voltage applied to the sensing cathode. This voltage parameter change creates a reverse bias condition that minimizes leakage current in the photoelectric conversion element, thereby maximizing the photocurrent signal when exposed to external light. The sensing driver dynamically adjusts these voltage parameters based on the emission control signal to optimize the balance between leakage current reduction and photocurrent generation
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 solution effectively reduces leakage current and enhances photocurrent generation, improving the performance and power efficiency of the display device while maintaining black gradation display capabilities.
Implementation Method 1
the sensor may include one or more photoelectric conversion elements for sensing light and converting the sensed light into an electrical signal
Data Source
AI summary
A display device includes a pixel including a display driver configured to apply a driving current to a light-emitting element; and an optical sensor including a sensing driver configured to apply a sensing current to a read-out line based on a photocurrent from the photoelectric conversion element, wherein the pixel further includes, a driving transistor configured to control the driving current, a first transistor configured to apply a first initialization voltage to an anode of the light-emitting element based on an emission control signal, and a second transistor configured to connect the anode of the light-emitting element to a first electrode of the driving transistor in accordance with the emission control signal, and wherein a channel of the first transistor is a different material from channels of the driving transistor and the second transistor.