efficient and stable oleds employing square planar metal ... · efficient and stable oleds...

DOE SSL R&D Workshop 2016

Efficient and Stable OLEDs Employing

Square Planar Metal Complexes and

Inorganic Nanoparticles

Jian Li

Arizona State University


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.


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)


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.


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)


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.


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)


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


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.


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)


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.


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).


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


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


• 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.

efficient and stable oleds employing square planar metal ... · efficient and stable oleds...

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