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.