On-screen fingerprint sensor with optically and electrically tailored transparent electrode patterns for use on...

Area of Science:

• Materials Science
• Electrical Engineering
• Optoelectronics

Background:

• Full-screen smartphone displays require integrated components like on-screen fingerprint sensors.
• Indium tin oxide (ITO) transparent conductors offer high transmittance but can interfere with display quality.
• Moiré patterns arise from interference between sensor patterns and display pixel arrays, degrading visual quality.

Purpose of the Study:

• To fabricate a mutual capacitive-type on-screen fingerprint sensor for full-screen smartphones.
• To minimize Moiré phenomenon and maintain signal sensitivity through optimized sensor pattern design.
• To demonstrate successful on-screen fingerprint sensing on a commercial smartphone prototype.

Main Methods:

• Fabrication of on-screen fingerprint sensors using ITO transparent conductors (~10 Ω/sq., ~94% transmittance).
• Numerical calculations to explore sensor pitches and rotation angles for optimal pattern design.
• Experimental evaluation to determine the final sensor design, including electrical connection of unit patterns.

Main Results:

• Identified sensor patterns that minimize Moiré patterns while preserving signal sensitivity.
• Developed a unit block by electrically connecting three unit patterns to amplify capacitance variations.
• Demonstrated successful on-screen fingerprint sensing using the optimized sensor pattern and block circuit driving.

Conclusions:

• An effective on-screen fingerprint sensor design was achieved by balancing transmittance, Moiré reduction, and signal sensitivity.
• The integration of optimized sensor patterns and circuit driving enables reliable fingerprint recognition on display panels.
• This technology facilitates the development of smartphones with minimal bezels and seamless full-screen displays.