Optical Haze Nanopaper Enhanced Ultraviolet Harvesting for Direct Soft-Fluorescent Emission Based on Lanthanide Complex Assembly and Oxidized Cellulose Nanofibrils

Optical haze nanopapers were fabricated based on a self-assembly process of lanthanide complexes with tris(2-benzimidazolylmethyl) amine (NTB) [(Tb(NTB)Cl3 and/or Eu(NTB)Cl3] and TEMPO-oxidized cellulose nanofibrils (tCNFs), using a subsequent simple blending-vacuum filtration method. These optical haze nanopapers were characterized in terms of visible light transmittance, efficiency of ultraviolet (UV) light harvesting, and soft-fluorescence emission. The lanthanide complexes acted as a light-scattering source to enhance optical haze (∼100%) and a light emitter to emit soft-fluorescence under a UV light-emitting diode (UV-LED, λex, 365 nm). Due to excellent light-scattering behavior induced by the optical haze nanopaper, UV harvesting efficiency was increased from 53% to 98%, and the absolute quantum efficiency was enhanced from 21% to 25%. The optical haze nanopaper with high efficiency UV harvesting and soft-fluorescent emission presented potential applications in solar cells, lampshades, light diffusers, UV-blocking devices, anticounterfeiting devices, and organic light-emitting diodes.