Synthetic
Metals
162 (2012) 1587–
1593
Contents
lists
available
at
SciVerse
ScienceDirect
Synthetic
Metals
journa
l
h
o
me
page:
www.elsevier.com/locate/synmet
Color-stable
deep
red-emitting
OLEDs
based
on
a
soluble
terpolymer
containing
fluorene,
thiophene
and
benzothiadiazole
units
Bo
Qu
a,∗
,
Limin
Feng
b
,
Hongsheng
Yang
a
,
Zhi
Gao
a
,
Chao
Gao
b,c,∗∗
,
Zhijian
Chen
a
,
Lixin
Xiao
a
,
Qihuang
Gong
a,∗
a
State
Key
Laboratory
for
Artificial
Microstructures
and
Mesoscopic
Physics,
Department
of
Physics,
Peking
University,
100871,
People’s
Republic
of
China
b
Xi’an
Modern
Chemistry
Research
Institute,
Xi’an,
Shaanxi
710065,
People’s
Republic
of
China
c
State
Key
Laboratory
of
Transient
Optics
and
Photonics,
Xi’an
Institute
of
Optics
and
Precision
Mechanics,
Chinese
Academy
of
Science
(CAS),
Xi’an,
Shaanxi
710119,
People’s
Republic
of
China
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
26
March
2012
Received
in
revised
form
23
May
2012
Accepted
22
June
2012
PACS:
78.55.Kz
78.60.Fi
78.66.Qn
Keywords:
Deep
red-emitting
OLED
Organic
electroluminescence
Terpolymer
Fluorene
Benzothiadiazole
Thiophene
a
b
s
t
r
a
c
t
A
novel
soluble
terpolymer
(P8FO-Th-BT)
containing
9,9-dioctylfluorene,
thiophene,
and
2,1,3-
benzothiadiazole
units
were
synthesized
by
Still
coupling
reaction.
The
single
layer
and
multi-layer
organic
light
emitting
diodes
(OLEDs)
based
on
P8FO-Th-BT
was
fabricated.
A
deep
red-emission
device
with
the
configuration
of
ITO/poly(3,4-ethylenedioxythiophene)-polystyrene
sulfonate
(PEDOT:PSS)/P8FO-Th-BT:N,N
-di(3-methylphenyl)-N,N
-diphenyl-(1,1
-biphenyl)-4,4-diamine
(TPD)
(weight
ratio
being
1:1)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline
(BCP,
15
nm)/tris(8-
hydroxyquinoline)
aluminum
(Alq
3
,
15
nm)/LiF(5
˚
A)/Al(150
nm)
was
obtained,
and
the
maximum
luminance
was
measured
to
be
226
cd/m
2
at
the
bias
voltage
of
10
V.
The
electroluminescent
peak
located
at
708
nm,
and
the
spectrum
covered
both
the
red
and
infrared
regions.
Moreover,
the
Commis-
sion
International
De
L’Eclairage
(CIE)
chromaticity
coordinates
of
the
device
were
inalterable
when
the
bias
voltage
varied,
which
was
beneficial
to
the
application
on
display.
Crown Copyright ©
2012 Published by Elsevier B.V. All rights reserved.
1.
Introduction
The
organic
light-emitting
diodes
(OLEDs)
have
attracted
considerable
attention
since
the
milestone
work
of
Tang
et
al.
[1].
OLEDs
have
good
characteristics
of
self-emission,
low
weight,
low
driving
voltage,
low
cost,
ultra-thin
thickness
and
high
lumi-
nance
[2,3].
Many
research
groups
pursue
the
investigation
of
OLEDs,
which
have
extensive
applications
such
as
novel
light
sources
and
full-color
flat
panel
displays
[3–5].
Leclerc
group
systematically
developed
a
series
of
fluorene-based
copoly-
mers.
Poly((5,5
-3
,4
-dihexyl-2,2
:5,2
:5
,2
-quinquethi-
ophene
1
,1
-dioxide)-alt-2,7-(9,9-dihexylfluorene))
(PFBTTOR-
BT)
[6],
poly((5,5
-(3
,4
-dihexyl-2,2
);
5
,2
-terthiophene
∗
Corresponding
author
at:
State
Key
Laboratory
for
Artificial
Microstructures
and
Mesoscopic
Physics,
Department
of
Physics,
Peking
University,
100871,
People’s
Republic
of
China.
Tel.:
+86
10
62767290;
fax:
+86
10
62756567.
∗∗
Corresponding
author
at:
Xi’an
Modern
Chemistry
Research
Institute,
Xi’an,
Shaanxi
710065,
People’s
Republic
of
China.
E-mail
addresses:
bqu@pku.edu.cn
(B.
Qu),
chaogao74@gmail.com
(C.
Gao),
qhgong@pku.edu.cn
(Q.
Gong).
1
,1
-dioxide))-alt-2,7-(9,9-dihexylfluorene))
(PFTORT),
poly((5,
5-E-␣-(2-thienyl)
methylene)-2-thiopheneacetonitrile)-alt-2,7-(9,
9-dihexylfluorene))
(PFTCNVT),
and
poly((5,5
-(3
,4
-dihexyl-
2,2
:5
,2
:5
,2
:5
,2
-quinquethiophene
1
,1
-dioxide))-alt-2,7-
(9,9-dihexylfluorene))
(PFTTORTT)
[7]
were
considered
as
novel
red-emitting
copolymers
for
OLEDs.
In
addition,
Liu
et
al.
reported
a
saturated
red
emitter
named
poly[9,9-dioctyl-2,7-fluorene-alt-
(4,7-bis(2
-thienyl)-2-octyl-2,1,3-benzotriazole)]
(PFDTBTz)
[8],
which
composed
of
dithienyl
benzotriazole
units
and
fluorene
units.
Fluorene-based
copolymers
of
P-DPP2,
P-DPP3,
P-DPP-T1
[9],
PF1R0
[10],
and
PFDP
[11]
all
exhibited
close
pure
red
emission.
Although
there
is
a
plethora
of
blue-
and
green-emitting
polymers
for
OLEDs
[12–15],
color-stable
red
emission
is
still
relatively
dif-
ficult
to
obtain
due
to
the
serious
concentration
quenching
effect
of
red-emitters
[9,16,17].
Therefore,
much
more
effort
should
be
devoted
to
the
research
of
red
emitting
OLEDs
[18–24].
In
this
work,
a
color-stable
deep
red-emitting
terpolymer
(P8FO-
Th-BT)
containing
fluorene,
thiophene
and
benzothiadiazole
units
was
synthesized
and
characterized.
The
optical,
electrochemical
and
electroluminescent
(EL)
properties
have
also
been
investigated
in
detail.
The
deep
red-emitting
diodes
based
on
P8FO-Th-BT
were
0379-6779/$
–
see
front
matter.
Crown Copyright ©
2012 Published by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.synthmet.2012.06.021