Biometric authentication security enhancement under quantum dot light-emitting diode display via fingerprint imaging and temperature sensing.

We improved biometric authentication security using dual recognition based on fingerprint image detection and skin-temperature-change sensing under quantum dot light-emitting diode (QLED) displays. QLEDs are more advantageous than organic light-emitting diodes (OLEDs) in terms of the contrast classification of patterns such as those in fingerprint recognition, owing to their narrow full-width-half-maximum. In this work, scattered, transmitted, and reflected light was captured from the top of the QLED, improving the digital luminance by 25%, as compared with that of OLEDs, because the electroluminescence spectra of the QLED were sustained, whereas those of the OLED were distorted by the generated noise peaks. A QLED with eight apertures sized up to tens of micrometers, mimicking the actual wiring structure of commercialized smartphones, was implemented to detect human fingerprints. The QLED using reduced graphene oxide as the temperature sensor detected temperature changes instantaneously upon finger touch, showing a 2% temperature response based on the human body temperature; however, the temperature change was less than 0.1% for spoof fingerprints printed on paper. Thus, this study successfully enhanced biometric authentication security, through fingerprint recognition based on image sensing using an optical system with micrometer-sized apertures and skin-temperature detection under QLED displays.

Color gamut change by optical crosstalk in high-resolution organic light-emitting diode microdisplays.

Herein, the color gamut change by optical crosstalk between sub-pixels in high-resolution full-color organic light-emitting diode (OLED) microdisplays was numerically investigated. The color gamut of the OLED microdisplay decreased dramatically as the pixel density of the panel increased from 100 pixels per inch (PPI) to 3000 PPI. In addition, the increase in thickness of the passivation layer between the bottom electrode and the top color filter results in a decrease in the color gamut. We also calculated the color gamut change depending on the pixel structures in the practical OLED microdisplay panel, which had an aspect ratio of 32:9 and a pixel density of 2,490 PPI. The fence angle and height, refractive index of the passivation layer, black matrix width, and white OLED device structure affect the color gamut of the OLED microdisplay panel because of the optical crosstalk effect.