Broadband Plasmonic Antenna Enhanced Upconversion and Its Application in Flexible Fingerprint Identification

Abstract

Plasmonic antennas based on metallic nanostructures that can trap long-wavelength light can be used to substantially enhance the efficiency of optoelectronic devices by utilizing light beyond the visible region. This study experimentally and theoretically demonstrates that a silver nanowire network (AgNW-net) plasmonic antenna exhibits superwide surface plasmon extinction because of the strong plasmon coupling between AgNWs, providing the ability to trap light spanning the entire solar spectrum. As a proof-of-concept demonstration, the AgNW-net is used to greatly improve the luminescence of lanthanide-doped upconversion nanocrystals (UCNCs) under dual wavelength excitation and the periodic alternating multilayer structure of AgNWs/UCNCs is further successfully introduced to improve the absolute luminescence intensity of AgNWs/UCNCs composite films. Furthermore, evidence has been provided that this improvement is attributable to excitation field enhancement rather than Purcell effect or plasmon-enhanced energy transfer. Finally, an upconversion flexible fingerprint identification technology is developed based on AgNW-net/UCNCs/polyvinyl alcohol composite materials, which allows us extracting fingerprints on various uneven bending surfaces.