Comparison of Device Performance in Two Thin-Film Electroluminescent Devices Made of Vacuum-Sublimed Dye Film and Spin-Coated Polymer Film

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Abstract
Electroluminescent (EL) characteristics in EL devices made of vacuum-sublimed dye films and spin-coated polymer films were compared. Low-molar-mass dye, 9,10-bis[4-(N,N-diphenylamino)styryl]anthracene (dye-BSA), for the preparation of vacuum-sublimed films, and polymer with 9,10-bis[4-(N,N-diphenylamino)-styryl]anthracene chromophore linked with alkylether groups (polymer-BSA) were employed. Single-layer devices, indium-tin oxide (ITO)/dye-BSA/MgAg and ITO/polymer-BSA/MgAg were prepared, and EL performances were compared. Double-layer devices which have an oxadiazole derivative (OXD-7) electron transport layer, ITO/dye-BSA/OXD-7/MgAg and ITO/polymer-BSA/OXD-7/MgAg, were also prepared. The current density-voltage relationships between dye-BSA devices and polymer-BSA devices were considerably different mainly due to the poor film quality of polymer-BSA. The comparisons of the luminance-current density relationships of the devices with two classes of BSA films showed that the polymer-BSA devices exhibited similar EL characteristics as the dye-BSA devices in the region of current density higher than 10 mA/cm2. The possibility of the use of common material design concept for low-molar-mass materials and polymers was discussed.