The wide full-width-half-maximum (FWHM) of the electroluminescence (EL) spectra of OLEDs exhibit flaws as an appropriate light source for fingerprint recognition based on skin reflectance. Although inorganic light-emitting diodes (LEDs) have an extremely narrow FWHM, it is difficult to fabricate self-emitting inorganic LED-based displays for mobile smartphones without color filters. A group of researchers improved biometric authentication security by employing dual recognition based on fingerprint image detection and skin-temperature change sensing in quantum dot light-emitting diode (QLED) displays.
Because of their narrow full-width-half-maximum, QLEDs outperform organic light-emitting diodes (OLEDs) in the contrast classification of patterns such as those used in fingerprint recognition. In this work, scattered, transmitted, and reflected light was captured from the top of the QLED, increasing digital luminance by 25% compared to OLEDs because the QLED’s electroluminescence spectra were sustained, whereas noise peaks distorted the OLEDs.
A QLED with eight apertures sized up to tens of micrometers was used to detect human fingerprints, which mimicked the actual wiring structure of commercialized smartphones. The QLED display, which used reduced graphene oxide as the temperature sensor, detected temperature changes instantly upon finger touch, displaying a 2% temperature response based on human body temperature; however, the temperature change was less than 0.1% for spoof fingerprints printed on paper.
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