OLED Fingerprint Sensor Using Thin Film Transistor Leakage Current
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Solution Overview
Problem
Current fingerprint identification sensing technologies in electronic devices are structurally complex, lack sensitivity, and are difficult to integrate with other device structures due to reliance on laser detection or capacitance methods, which require additional components and result in slow sensing times.
Innovation Solution
A fingerprint identification sensor utilizing an OLED light source and a thin film transistor, where the light emitted from the OLED irradiates onto a finger, causing reflected light to affect the off-state leakage current of the transistor, allowing for sensitive and efficient fingerprint recognition without increasing device volume, and can be integrated with array substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser detection or capacitance methods are used for fingerprint identification, then fingerprint recognition can be achieved, but the device becomes structurally complex and requires additional components
Solution Approach 1:
The patent combines the light source (OLED) and the sensing element (thin film transistor) into a single integrated structure. The thin film transistor serves dual purposes: as part of the display structure and as the fingerprint sensing element. This merging eliminates the need for separate laser detection components and capacitance sensing electrodes, thereby reducing device complexity while maintaining fingerprint recognition capability.
Solution Approach 2:
The thin film transistor is designed to perform multiple functions: it acts as both a display pixel element and a fingerprint sensing element. By making the sensing element universal (capable of both display and sensing), the patent eliminates the need for dedicated separate components, thus reducing overall device complexity while preserving reliable fingerprint recognition.
2Reliability
If laser detection or capacitance methods are used for fingerprint identification, then fingerprint recognition can be achieved, but the sensing time is prolonged and sensitivity is limited
Solution Approach 1:
The patent replaces traditional mechanical/optical detection methods (laser detection) with an electrical field-based detection method using the thin film transistor's off-state leakage current. This substitution enables faster response time because electrical field detection occurs almost instantaneously compared to optical detection, thereby reducing sensing time while maintaining high sensitivity and reliable fingerprint recognition.
3Reliability
If traditional fingerprint sensing methods are used, then fingerprint identification can be performed, but the device volume increases due to additional components
Solution Approach 1:
The patent merges the fingerprint sensing function with the existing display structure by using the thin film transistor for both purposes. This integration means that no additional space is required for separate sensing components, thereby preventing device volume increase while maintaining full fingerprint identification capability.
Solution Approach 2:
By designing the thin film transistor to serve dual functions (display and fingerprint sensing), the patent eliminates the need for additional dedicated components that would increase device volume. The universal design allows the same structure to perform multiple functions without requiring extra space, thus maintaining compact device dimensions while preserving reliable fingerprint identification.
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 provides a high-sensitivity, structurally simple fingerprint identification method that enhances accuracy and speed, allowing for seamless integration into electronic devices without bulkiness, with the ability to distinguish between fingerprint ridges and valleys through significant differences in leakage currents.
Implementation Method 1
the fingerprint identification sensor can use a light source, such as an OLED light source, and a thin film transistor as a fingerprint sensing element. Light emitted from the light source irradiates onto a finger to generate a reflected light
Implementation Method 2
the lights reflected by different parts of the finger may have different light intensities, which may affect an off-state leakage current of the thin film transistor
Data Source
AI summary
A fingerprint identification sensor, a fingerprint identification method and an electronic device are disclosed. The fingerprint identification sensor includes a substrate; a fingerprint sensing element disposed on the substrate and including a thin film transistor, an off-state leakage current of the thin film transistor varying with the intensity of light irradiating onto an active area thereof; and a fingerprint identification light source arranged to emit light that irradiates onto a finger and is reflected thereby, the reflected light irradiating onto the active area of the thin film transistor. Thus, the fingerprint identification can be realized conveniently, and the fingerprint identification sensor has at least one of the advantages like high sensitivity and simple structure.