Researchers develop display screens with biometric sensor capabilities

Traditional display screens like those built into smartphones require extra sensors for touch control, ambient light, and fingerprint sensing. These additional sensors increase the cost and design complexity, limiting the development of screens with a large screen-to-body ratio.

Researchers at Linköping University, Sweden, however, have introduced a multifunctional display that can perform all of these roles simultaneously without the need for additional sensors. This not only simplifies the display structure but also enhances its functionality. The research paper showcases an innovative solution for developing a display system using photo-responsive metal halide perovskite light-emitting diodes (PeLEDs) as pixels.

By integrating multiple functionalities, the display can be used not only as a visual output device but also as an image sensor capable of capturing fingerprint biometrics, and even a photovoltaic device capable of charging equipment.

Under-display biometrics on smartphones and tablets are currently provided by optical or ultrasonic sensors placed under the screen.

“We’ve now shown that our design principle works. Our results show that there is great potential for a new generation of digital displays where new advanced features can be created. From now on, it’s about improving the technology into a commercially viable product,” says Feng Gao, professor in optoelectronics at Linköping University (LiU).

After evaluation, researchers have identified a challenge with current display technologies, specifically LCDs and OLEDs, as they lack robust sensing capabilities within their pixels. While cadmium selenide nanocrystals offer photosensitivity, a trade-off between light absorption and charge transport limits their effectiveness.

As an alternative, Perovskite LEDs have been proposed due to their high brightness, flexible manufacturing, and excellent optical absorption and carrier transport. These PeLEDs are capable of emitting light under forward bias and detecting light effectively, making them a compelling solution for multifunctional displays.

“Traditionally, a fingerprint can only be input within a specific area of the screen where the fingerprint sensor is positioned,” researchers explain. The Perovskite multifunctional display is photoresponsive, enabling input capability expansion across the entire screen area. During the proof-of-concept stage, researchers utilized this technology by enlarging a fingerprint drawn on paper.

“The result indicates the great potential of using our multifunctional display for future on-screen multi-point fingerprint recognition on increasing the display resolution,” researchers note.

Article Topics

biometric sensors  |  biometrics  |  display screen  |  fingerprint sensors  |  LED  |  Perovskite LED