Phenyl-substituted polymer electroluminescent (EL) devices using an insulat
ing lithium-fluoride (LiF) layer between indium tin oxide (ITO) and poly(st
yrene sulfonate)-doped poly(3,4-ethylene dioxythiophene) (PEDOT) hole trans
porting layer have been fabricated. By comparing the devices made without t
his layer, the results demonstrate that the former has a higher EL brightne
ss operated at the same current density. At a given constant current densit
y of 20 mA/cm(2), the luminance and efficiency for devices with 1.5 nm LiF-
coated ITO were 1600 cd/m(2) and 7 cd/A. These values were 1170 cd/m(2) and
5.7 cd/A, respectively, for the same devices made with only an ITO anode.
The ultrathin LiF layer between ITO and PEDOT modifies the hole injection p
roperties. A more balanced charge carrier injection due to the anode modifi
cation by an ultrathin LiF layer is used to explain this enhancement. (C) 2
001 American Institute of Physics.