Abstract
In the fierce market competition of different biometric methods in smartphones, where consumers are pursuing a high screen ratio, optical fingerprint recognition under OLED screen is a well-established approach. However, using thin-film transistor (TFT) technology to make large-area optical sensors generally has the issue of low sensitivity, which will make the signal difficult to be read out. In this paper, we propose to use gap-type TFT with high photosensitivity current and process compatible with display panels as the sensing device to build the sensing array. The pixel circuit can be simplified to structure containing only of two thin-film transistors (TFTs). Using this gap-type TFT sensing array under OLED panel for fingerprint recognition is proven to be effective by the clear images captured with the readout system.
Highlights
Nowadays, smartphone is an indispensable mobile device in human daily life
We consider that gap-type thin-film transistor (TFT) is the best optical device in the under-screen fingerprint sensor for its good sensitivity and low cost owing to the high photocurrent and fully TFTcompatible process [10] and [11]
A system with the gap-type TFT for the optical sensing array, the array under OLED panel with collimator in between, and the readout circuit is built to demonstrate the good performance in fingerprint image capture
Summary
Smartphone is an indispensable mobile device in human daily life. Many functions and applications require biometrics recognition to ensure personal information security. INDEX TERMS Fingerprint sensor, gap-type, photocurrent, thin film transistor (TFT).
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