LIGHT-EMITTING-DIODES FROM DYE-INSULATING MATRIX LANGMUIR-BLODGETT-FILMS

Light-emitting diodes (LEDs) utilizing a dye-insulating matrix blend h ave been fabricated with the Langmuir-Blodgett technique. The emitting dye material used was Rubrene, while poly(methylmethacrylate) (PMMA) was used as the insulating matrix material. The luminance-current dens ity characteristics were studied as a function of Rubrene/PMMA molar r atio which ranged from 5:95 to 60:40 mol.% of Rubrene/PMMA. Devices wi th low concentrations of Rubrene were found to emit approximately the same amount of light as devices containing higher concentrations of th e emitting material. The thickness dependence of luminance vs, applied voltage was studied for devices with 'optimal' molar ratio between Ru brene and PMMA. The thickness of the LEDs studied ranged from three to 11 molecular layers. Photoluminescence and electroluminescence spectr a of the LEDs were compared. The quantum efficiency for the LED config uration was calculated. (C) 1998 Elsevier Science S.A. All rights rese rved.