Photosensitive Component Under TFT Layer for In-Cell Fingerprint Sensing
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Solution Overview
Problem
Conventional fingerprint sensors in display panels affect the array process technology and aperture ratio, and their sensitivity is lower due to the complexity and cost of integration, especially in portable devices like mobile phones, and they struggle with accurate recognition under ambient light interference.
Innovation Solution
A display panel design with a color filter on array process, where the photosensitive component is placed on the counter substrate's light-emitting surface, reducing the distance between the sensor and the fingerprint, and utilizing a PIN-type photodiode for improved light energy differentiation between ridges and valleys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional optical fingerprint sensor is integrated into a display panel, then fingerprint recognition function is added, but the aperture ratio of the display panel is reduced and the array process technology is affected
Solution Approach 1:
The patent merges the fingerprint sensor and display panel into a single integrated structure. The photosensitive component is formed on the same substrate as the liquid crystal display panel, with the photosensitive layer integrated into the display panel's layered structure. This allows the fingerprint sensor to share the same aperture space as the display, eliminating the need for separate sensor area and thus maintaining high aperture ratio while providing fingerprint recognition function.
Solution Approach 2:
The display panel is designed to serve multiple functions: display function through the liquid crystal layer and light source, and fingerprint recognition function through the photosensitive component. The same optical path is used for both display illumination and fingerprint sensing, allowing one device structure to fulfill multiple purposes without requiring additional dedicated space for either function.
2Reliability
If a conventional optical fingerprint sensor is used, then fingerprint recognition is possible, but the sensitivity is lower due to twice absorption of the liquid crystal
Solution Approach 1:
Instead of placing the photosensitive component on one side of the liquid crystal layer and the light source on the other side (causing light to pass through liquid crystal twice), the patent inverts the arrangement by placing both the light source and photosensitive component on the same side of the liquid crystal layer. This allows the illumination light to pass through the liquid crystal layer only once to reach the finger, and the reflected light to return through the liquid crystal layer once, eliminating the double absorption problem and improving sensitivity.
3Shape
If the photosensitive component is placed far from the fingerprint, then the display structure is maintained, but the light energy difference between ridges and valleys is extremely small
Solution Approach 1:
The patent creates an optical path that effectively brings the photosensitive component close to the fingerprint by using the reflected light path. The illumination light passes through the display panel to reach the finger, and the reflected light returns through the same path to the photosensitive component. This optical copying approach allows the photosensitive component to be positioned within the display panel structure while achieving close proximity to the fingerprint for accurate light energy differentiation.
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 design enhances the aperture ratio, improves fingerprint recognition sensitivity, and enables accurate in-cell fingerprint sensing under the liquid crystal display panel, providing a better unlocking experience.
Implementation Method 1
the photosensitive component is configured to receive a reflected light of a fingerprint of a user to identify an identification of the user
Implementation Method 2
the amorphous silicon photodiode generates electron-hole pairs when light signal is incident on the amorphous silicon photodiode
Data Source
AI summary
A display panel and a display device are provided, which the display panel including a display substrate, a counter substrate, and a backlight. The display substrate includes a first thin film transistor layer, a touch electrode, and a pixel definition layer. The substrate includes a second thin film transistor layer and a photosensitive component. The second thin film transistor layer has a plurality of thin film transistors. The photosensitive component is connected to an underside of the second thin film transistor layer. The photosensitive component receives a reflected light of a user's fingerprint to identify an identification of the user.