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DOE SSL R&D Workshop 2016
Efficient and Stable OLEDs Employing
Square Planar Metal Complexes and
Inorganic Nanoparticles
Jian Li
Arizona State University
DOE SSL R&D Workshop 2016
Progress of Excimer-based WOLEDs
Fleetham et al. Adv. Mater. (2013)
300 400 500 600 700 800
NN
Pt
Cl
N N
N
F
F
Pt
O
OCIE (.44, .45)
CRI - 75
CIE(.33, .35)
CRI - 53
Wavelength (nm)
CIE(.33, .33)
CRI - 80
NN Pt
Cl
F F
Pt-4
Pt-16
FPt
For Pt-16 WOLED, power efficiency exceeds 50 lm/W
(no n/p-doping and enhanced coutcoupling), CIE
(0.33, 0.32), CRI >=80, showing promise for lighting
applications.
Power efficiency is 29 lm/W at 1000 cd/m2
1E-4 1E-3 0.01 0.1 1 100
5
10
15
20
25
EQ
E (
%)
J (mA/cm2)
PO15 (40 nm)
PO15(10nm)/BmPyPB(30nm)
device structure:ITO/PEDOT:PSS/NPD(30nm)/TAPC(10nm)/
10%Pt-16:TAPC:PO15(25nm)/ ETL/LiF/Al.
DOE SSL R&D Workshop 2016
Pt7O7- Both Efficient Monomer and Excimer Emission
0.1 1 10 100 1000 10000
0
5
10
15
20
25
30
2% Pt7O7
14% Pt7O7
18% Pt7O7
EQ
E (
% P
ho
ton
/ele
ctro
n)
Brightness (cd/m2)
ITO/HATCN(10nm)/NPD(30nm)/TAPc(10nm)/x%Pt7O7:mCBP
(25nm)/DPPS(10nm)/BmPyPB(40nm)/LiF/Al.
Our Pt7O7 data suggest that both monomer and excimer can have PL quantum
efficiency of close to 100%.
400 500 600 700 800
0.0
0.5
1.0
EL
In
ten
sity (
a.u
.)
Wavelength (nm)
2% Pt7O7
CIE: (0.12, 0.24)
14% Pt7O7
CIE: (0.37, 0.43)
CRI: 70
18% Pt7O7
CIE: (0.41, 0.45)
CRI: 70
Li et al. Adv. Mater. (2014)
DOE SSL R&D Workshop 2016
Recent Update of Excimer-Based WOLED
400 500 600 700 8000.0
0.5
1.0
NN
O
NN
Pt
14% Pt2O2:mCBP/HBL
mCBT
BAlq
EL
In
ten
sity (
a.u
.)
Wavelength (nm)
0.01 0.1 1 10 100 10000
5
10
15
20
25
14% Pt2O2:mCBP/HBL
mCBT
BAlq
EQ
E (
% P
ho
ton
/ele
ctr
on
)
Luminance (cd/m2)
1) maximum efficacy @ 50 lm/W ,
2) CRI ~70, EQE > 17% and LT50 >1000 hrs @1000 cd/m2 on a standard
glass substrate.
DOE SSL R&D Workshop 2016
Material Design for Blue Emitters Based on Pt Complexes
Replace pyridine with azole groups to raise LUMO
Break conjugation with
6-membered chelating rings
Add electro
n withdrawing
groups to lo
wer HOMO
N
F
F
N
IrN
O O
2FIrpic
NN
Pt
N
O
N
NN
Pt
O
NN
PtNON
PtON1
N NPt
Cl
F F
N
N
Ir
3
Irpmi
Pt-4
O
NN
NN
Pt
PtON2
Ir
3
Ir(ppy)3
blue emitters with green triplet energy (MADF material concept)
DOE SSL R&D Workshop 2016
Complex λmax (nm) Φ(%) τ
(μs)
kr
(x104 s-1)
knr
(x104 s-1)
PtON7 452 89 4.1 21 2.6
PtOO7 442 58 2.5 23 17
Pt-16[9b] 450 32 5.1 6.3 13.3
Pt(Mepmic)[9a] 419 20 25 0.8 3.2
Ir(cnpmic)3[7b] 425(sh), 450 78 19.5 4 1.1
Ir(dbfmi)[7a] 445 70a 19.6 3.6 1.5
PtON1 449 85 4.5 19 3.3
Blue Emitting Pt vs. Ir Complexes
Hang et al. Angew Chem. Int. Ed. (2013)
O
O
N
Pt
PtOO7 PtON7
N
N
N
O
N
PtN
N
O
O
PtN
N
N N
N NPt
Cl
Pt-16
Pt(Mepmi)
Pt[pmi-O-POPy] Pt[pmi-O-CbPy]
IrN
N
Ir(dpfmi)
O
33
N
N
CN
Ir
Ir(cnpmic)
• With such molecular design principle, PtON7
shows a better photophysical properties than
its Pt analogs and Ir analogs;
• A deep blue OLED with a maximum EQE of
22% and CIE coordinates of (0.14, 0.15) was
fabricated using PtON7.
400 500 600 700 8000
1
Ele
ctr
olu
min
escence (a
.u.)
Wavelength (nm)
Device 1
(Pt-16)
CIE: (0.16,0.15)
400 500 600 700 8000
1
E
lectr
olu
min
escence (
a.u
.)
Wavelength (nm)
Device 2
(PtOO7)
CIE: (0.15,0.10)
400 500 600 700 8000
1
Ele
ctr
olu
min
escence (a
.u.)
Wavelength (nm)
PtON7
Device 3
CIE: (0.14,0.19)
Device 4
CIE: (0.14,0.15)
1E-3 0.01 0.1 1 10 1000
10
20
Exte
rnal Q
uantu
m E
ffic
iency (
%)
Current Density (mA/cm2)
Device 1
Device 2
Device 3
Device 4
ITO/PEDOT:PSS/NPD(30 nm)/TAPC(10 nm)/2% emitter:26mCPy(25
nm)/PO15(40 nm)/LiF/Al.
DOE SSL R&D Workshop 2016
RGB Narrowband Phosphorescent Emitters
400 500 600 7000.0
0.5
1.0
EL
In
ten
sity (
a.u
.)
Wavelength (nm)
PtON7-t-Bu
PtN1N
PtN8PPy
400 500 600 700
0.0
0.5
1.0P
L in
ten
sity (
a.u
.)
Wavelength (nm)
PtON7-t-Bu
PtN1N
PtN7N
PtN8ppy
0.01 0.1 1 10 100 10000
5
10
15
20
25
EQ
E (
%)
Brightness (cd/m2)
PtON7-t-Bu
PtN1N
PtN8ppy
N
N
O
N
N
Pt
N
N
N
N
N
Pt
NN
N
Pt
N
PtON7—t-Bu
PtN7N
PtN8ppy
0.0 0.2 0.4 0.6 0.8
0.0
0.2
0.4
0.6
0.8
1.0
1
2
3
4
1 PtON7-t-Bu
2 PtN1N
3 PtN7N
4 PtN8ppy
y
x
PtN7N
PtON7—t-Bu
ITO/HATCN/NPD(30 nm)/TAPC(10 nm)/x%
emitter:26mCPy(25 nm)/DPPS(10 nm)/BmPyPB(30 nm)LiF/Al.
N
N
N
N
N
Pt
NN
N
Pt
N
N
N
O
N
N
Pt
PtN7N
PtN8ppy
PtON7-t-Bu
Li et.al., Adv. Opt. Mater. (2015)
DOE SSL R&D Workshop 2016
0.1 1 10 100 1000
0
5
10
15
20
25
EQ
E (
% p
h/e
- )
Luminance (cd/m2)
Metal-Assisted Delay Fluorescent Emitters
N
N
N
N
P d
P d N 3 N
400 500 600 700 800
0.0
0.5
1.0
EL
In
ten
sity (
a.u
)
Wavelength (nm)
ITO/HATCN/NPD(30 nm)/TAPC(10 nm)/6%
PdN3N:CBP (25 nm)/DPPS(10 m)/BmPyPB
(30 nm)LiF/Al.
Zhu et.al., Adv. Mater. (2015)
Blue-emitting MADF emitter with green triplet energy
could be most energetically favorable.
S 1 I S C
T 1
M e t a l A s s i s t e d D e l a y e d F l u o r e s c e n c e ( M A D F )
S 0
S 1 I S C T 1
p h o s p h o r e s c e n c e
S 0
Limit set by
carbazole
host
S 1 I S C T 1
T h e r m a l A c t i v a t e d D e l a y e d F l u o r e s c e n c e ( T A D F )
S 0
DOE SSL R&D Workshop 2016
Operational Stability of Pt Complexes
Li et.al. ACS Appl. Mater. Interface (2015)
ITO/HATCN(10 nm)/NPD(40 nm)/EML(25 nm)/
BAlq(10 nm)/BPyTP(40 nm)/LiF/Al.
DOE SSL R&D Workshop 2016
Horizontally Aligning Pt Complexes for Improved Light Extraction
substrate
substrate
(a)
(b)
Standard OLED EQE could be improved to 45% if 100% horizontally oriented emitting
dipoles. Square planar metal complexes with in-plane emitting dipoles could have a
better control of molecular orientation. Such molecular orientation approach adds zero
cost to OLED fabrication. K. H. Kim Adv. Opt. Mater. (2015) & Q. Wang Adv. Mater. (2014)
DOE SSL R&D Workshop 2016
Narrowband vs Broadband Emitters in Tuned MCOLEDs
400 450 500 550 600 650 7000.00
0.25
0.50
0.75
1.00
1E-5 1E-4 1E-3 0.01 0.1 1 10 1000
5
10
15
20
25
30
35
PtOO3:26mCPy
PtN1N:26mCPy
Th
in F
ilm
PL
Sp
ectr
a (
A.U
.)
Wavelength (nm)
PtOO3 in Conventional OLED
PtOO3 in MOLED
PtN1N in Conventional OLED
PtN1N in MOLED
b
Exte
rna
l Q
ua
ntu
m E
ffic
ien
cy (
%)
Current Density (mA/cm2)
a
Ecton et al. In preparation.
Narrowband phosphorescent emitter makes MCOLEDs an effective approach for
light extraction enhancement purpose.
DOE SSL R&D Workshop 2016
Material Focused Light Extraction Enhancement Approaches
AUDI Taillight Concept
100% horizontally oriented narrowband phosphor-
escent emitters in the microcavity OLED with
external extraction layer will enable the EQE of
monochromic OLED over 70% (suitable for
signage and taillight applications).
100% horizontally oriented blue narrowband
phosphorescent emitters in the microcavity OLED
with external extraction layer will enable the EQE
of white OLED over 70% (suitable for general
illumination applications).
DOE SSL R&D Workshop 2016
Semiconductor Colloidal Quantum Dots
• Size- and composition-dependent tunable
emission through visible spectrum
(quantum confinement effect)
• Narrow emission peaks (minimum width
~20 nm)
• High luminescence quantum yield (~90%)
• Solution processible; good stability
CIE
Y
CIE X
NTSC Standard
▲ QLED
Versatile for solid-state lighting;
potential for high CRI and high efficacy
CRI=90, LER= 360 lm/W
DOE SSL R&D Workshop 2016
Cd1-xZnxSe1-ySy
x,y↑ 6-7nm
Solution-Processed QD-LEDs
GlassITO
PEDOT:PSS
TFB
CdSe-ZnS
QDs
ZnO NPs
Aluminum
Light Out
Color λmax
(nm)
FWHM
(nm)
Max. Lum.
(cd/m2)
ηEQE
(%)
ηP
(lm/W)
ηA
(cd/A)
Blue 455 20 4,000 10.3 2.7 4.3
Green 537 29 14,000 14.3 58 62
Red* 625 28 21,000 12.0 17.4 15
10-1
100
101
102
103
104
0
2
4
6
8
10
12
14
16
B
G
R
E
QE (
%)
L (cd/m2)
EQE > 10% achieved in QLEDs for all three colors
QLEDs operate more efficiently at high luminances
Low operation voltage good lm/W efficiency
Possible lifetime improvement (PEDOT:PSS, HTL, etc.)
L. Qian et al., Nat. Photon. 5, 543 (2011); Y. Yang et al., Nat. Photon. 9, 259 (2015).
* All efficiencies @ 1000 cd/m2
DOE SSL R&D Workshop 2016
• Future Outlooks for Single-doped WOLEDs Future Outlooks
• The development of stable blue emitters is key;
• The choice of excimers should include phosphorescent materials,
thermal activated delayed fluorescent (TADF) materials and metal-
assisted delayed fluorescent (MADF) materials;
• Square planar metal complexes could play a role of improving light
extraction efficiency of OLEDs;
• The recent progress of QLEDs has demonstrated enough promise
as a future solution for solution processed organic solid state lighting
devices.