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The
interested in
solid state organic light emitting materials has increased in the
research
community as well as in the industry due to a large demand for display
with
better color, thinner and better power efficiency.
A
lot of improvement have been done since
1980 when the first solid-state material where used to produce light. The
approach of our group is to provide some
chemistry insight into the devices fabrication and designing of
molecules. The judicious designing
of new
material
or/and the modifications of the periphery of ligands allows us to
improve film
morphology and devices properties: like color, turn-on time and
efficiency. This is done in
collaboration with Prof. Malliaras in the Material Science Department, Cornell University.
A
number
of symmetric [Ru(bpy)3]2+ (bpy =
2,2’-bipyridine) analogues have been synthesized and employed
in
electroluminescence devices achieving improvement in film morphology
and device
performance. The properties of
this
device are assessed by measuring turn-on time, radiance and efficiency. This
performance appears to be dominated
by
ionic current (diffusion) and ionic space charge effects.
As
a result, bulky side chains in the ligands
appear to have a large effect within the film, obtaining larger turn-on
time
and better efficiency than [Ru(tbubpy)3]2+. Also,
we have synthesized a group of osmium
complexes with diimine and phosphine achieving color tuning of several
hundred
nanometer. Here, we have carried
out
broad studies of these materials for OLED applications and report on
how film
morphology, turn-on time, and device performance can be varied and/or
controlled via synthetic variations in the periphery of the ligands. |
