Semi-transparent reduced graphene oxide temperature sensor on organic light-emitting diodes for fingerprint liveness detection of smartphone authentication

We report a semi-transparent temperature sensor for fingerprint liveness detection on an organic lightemitting diode (OLED). Solution-processable graphene oxide was coated between two indium tin oxide electrodes on a glass substrate, and a semi-transparent reduced graphene oxide (rGO) temperature sensor was successively fabricated through graphene oxide (GO) reduction using a laser source. The rGO temperature sensor showed a resistance variance characteristic of 80 % compared to the initial resistance when heated from 15 degrees C to 170 degrees C. When finger was touched on the rGO temperature sensor, the resistance variation was 0.5 % and 7 % at 35 degrees C and 50 degrees C, respectively. In addition, GO was coated on the light-emitting side of green phosphorescent OLEDs to investigate the damage caused by photothermal reduction energy. The OLEDs irradiated by the laser source for GO reduction showed nearly the same current-voltage characteristics and electroluminescence spectrum as the device without laser irradiation, although the luminance of the device decreased due to the absorption of rGO. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A semi-transparent temperature sensor was fabricated on an OLED for fingerprint liveness detection, showing significant resistance variation when touched by a finger. The effect of photothermal reduction energy on GO in OLEDs was investigated, resulting in decreased device luminance. Despite the absorption of rGO, the current-voltage characteristics and electroluminescence spectrum remained similar to devices without laser irradiation.