Sensing Transistor Gate Positioning for Optical Sensing in Display Panels
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Solution Overview
Problem
Existing display devices face challenges in integrating optical sensing functions within a narrow bezel design while protecting display driving elements from light and enhancing sensing performance.
Innovation Solution
Incorporating a sensing transistor in subpixels with a specific circuit structure that allows optical sensing without affecting display driving operations, where the gate electrode of the sensing transistor is positioned opposite to the light incident surface and the gate electrode of the display driving transistor blocks light, enabling effective optical sensing and improved photo-responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a photosensor is disposed in the bezel of the display panel, then optical sensing function can be provided, but the bezel area cannot be reduced
Solution Approach 1:
The patent merges the optical sensing function with the display panel's active area by integrating a sensing transistor and photosensor into the subpixel structure. This combination allows the sensing function to be performed within the display area itself, eliminating the need for separate bezel-mounted photosensors and thereby reducing bezel area while maintaining sensing capability
Solution Approach 2:
The subpixel structure is designed to serve dual functions: display function through the display transistor and light-emitting element, and sensing function through the sensing transistor and photosensor. This multi-functionality enables the same physical structure to perform both display and optical sensing tasks, resolving the contradiction between providing sensing function and reducing bezel area
2Object-affected harmful factors
If the gate electrode of the display driving transistor is disposed between the active layer and the light incident surface, then light blocking protection is achieved, but the active layer cannot respond to light for sensing
Solution Approach 1:
The patent segments the transistor structure into two distinct types: display transistors with gate electrodes positioned to block light and protect the active layer, and sensing transistors with gate electrodes positioned to allow light transmission to the active layer. This segmentation allows each transistor type to be optimized for its specific function without compromise
Solution Approach 2:
Different gate electrode positioning configurations are applied locally to different transistor types within the same pixel structure. Display transistors use one configuration (gate between active layer and light incident surface) for protection, while sensing transistors use another configuration (gate on opposite side) for light responsiveness, achieving both protection and sensing performance in the same local area
3Adaptability or versatility
If a sensing transistor is disposed in subpixels, then optical sensing can be performed in active area, but display driving operation may be affected
Solution Approach 1:
The pixel circuit is segmented into distinct display driving transistors and sensing transistors with separate gate control. This segmentation allows independent control of display and sensing functions, enabling the sensing transistor to be activated only during sensing periods while the display transistor maintains normal display operations, thus preventing interference between the two functions
Solution Approach 2:
The sensing transistor is activated periodically during specific sensing periods rather than continuously. During display periods, the sensing transistor remains inactive, allowing normal display driving operations. This periodic activation enables optical sensing functionality while maintaining reliable display performance 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 solution enables optical sensing in the active area of the display panel without impacting display driving operations, providing enhanced sensing performance and reducing bezel size by utilizing a sensing transistor that generates an off-current in response to light, allowing for accurate luminance and fingerprint sensing.
Implementation Method 1
a sensing transistor disposed in each of the plurality of subpixels... a sensing transistor generating an off-current in response to light
Implementation Method 2
the gate electrode of a display driving transistor may be disposed between an active layer and a light incident surface, thereby blocking light entering the display panel from arriving at the active layer of the driving transistor
Data Source
AI summary
A display device can include a display panel including a plurality of gate lines, a plurality of data lines and a plurality of subpixels; at least one display driving transistor disposed in each of the plurality of subpixels; a sensing transistor disposed in each of the plurality of subpixels; a driver circuit configured to control the sensing transistor; and a sensing circuit electrically connected to a first electrode of the sensing transistor, in which a gate electrode of the at least one display driving transistor and a gate electrode of the sensing transistor are disposed on opposite sides of an active layer in a top-down direction.