  Concentration quenching is a major impediment to efficient organic
light-emitting devices. We herein report on Organic Light-Emitting Diodes
(OLEDs) based on a fluorescent amorphous red-emitting starbust triarylamine
molecule (4-di(4'-tert-butylbiphenyl-4-yl)amino-4'-dicyanovinylbenzene, named
FVIN), exhibiting a very small sensitivity to concentration quenching. OLEDs
are fabricated with various doping levels of FVIN into Alq3, and show a
remarkably stable external quantum efficiency of 1.5% for doping rates ranging
from 5% up to 40%, which strongly relaxes the technological constraints on the
doping accuracy. An efficiency of 1% is obtained for a pure undoped active
region, along with deep red emission (x=0.6; y=0.35 CIE coordinates). A
comparison of FVIN with the archetypal DCM dye is presented in an identical
multilayer OLED structure.
