Novel red organic electroluminescent materials including perylene moiety

We have reported organic electroluminescent (EL) materials with functionall y separated molecular structure, which are composed of a luminescent center such as a fused aromatic ring and charge transfer units such as styryl-sub stituted diphenyl amino groups. This structure is a key to the design of li ght-emitting materials with controllable EL characteristics. Thus, we have already reported that a naphthalene moiety designed as a luminescent center with styryl-substituted diphenylamino groups as charge transfer unit gives blue light emission with high efficiency [A. Oda, E. Hasegawa, Mel. Electr on. Bioelectron. 10 (1999) 12 (in Japanese)]. In this report, we describe t he application of a perylene moiety to this structure to obtain red-light-e mitting materials. Triple-layered EL devices using five perylene compounds with or without a styryl substituent on diphenylamino groups have a maximum brightness of 4800 to 8700 cd/m(2). In the case of styryl-substituted comp ounds, the devices have orange to reddish-orange emission with peaks at abo ut 580 nm and shoulders at about 620 nm. Due to the shoulders at longer wav elength side of peaks, the CIE coordinate of the emission of a device shift s to (0.64, 0.35), which is almost the same as that of the red color of CRT . Thus, our molecular design method is proved to be useful for controlling color emission from blue to red. On the other hand, devices using compounds without a styryl. substituent have yellowish-green to yellow emission and peaks at about 560 nm. We examined the effects of the substitution on the e nd of the charge transfer unit. The current density vs. applied voltage cha racteristics of the devices are affected by methyl substitution on styryl g roups. The efficiencies are almost independent of the current density in th e devices with styryl-substituted compounds, but rapidly decrease in the ca se of compounds without a styryl substituent. (C) 2000 Elsevier Science S.A . All rights reserved.