junji adachi, kyushu university

Cathode

Anode

ETL

EML

HTL -＋

-＋

-‐‑‒＋100nm

3rd Genera6on

Delayed Fluorescence IQE~100%

1st Genera6on

Fluorescence IQE~25%

3.5th Genera6on

Hyper Fluorescence IQE~100%

2nd Genera6on

Phosphorescence IQE~100%

TADF TADF + Fluorescence

1987~ 2000~ 2012~ 2014~

DOE SSL R&D Workshop

OPERA research team KYUSHU UNIVERSITY Chihaya Adachi Junji Adachi 1

High Performance TADF for OLEDs

i)  Molecular design for high efficiency TADF and their applicaGon for OLEDs ii)  A new route for triplet harvesGng using TADF molecules as assistant dopant and fluorescence molecules as emiLer (Hyperfluorescence) iii) Triplet exciton management for reduced roll-‐off and device stability

2

Cathode

Anode

ETL

EML

HTL -＋

-＋

-‐‑‒＋100nm

3rd Genera6on

Delayed Fluorescence IQE~100%

1st Genera6on

Fluorescence IQE~25%

3.5th Genera6on

Hyper Fluorescence IQE~100%

2nd Genera6on

Phosphorescence IQE~100%

TADF TADF + Fluorescence

OUTLINES

1987~ 2000~ 2012~ 2014~

3

Principle of Conventional Emitting Process

h+ e-

25% 75%

Low Efficiency Low Cost

Unlimited Design Deep Blue

High Efficiency High Cost

Limited Design Deep Blue

λ∝HSO

ΔESTFirst-order mixing

coefficient between singlet and triplet states (λ)

Hso: Spin-orbit coupling

Larger λ provides larger probability for transition between S1 and T1 states.

4

Principle of TADF

ES=(EH-‐EL)+K ET=(EH-‐EL)-‐K

ΔEST=2K

EH :HOMO Energy EL : LUMO Energy K :Exchange Energy

・ Small ΔEST

φ φ φ φ τ τ= ∫∫ 1 212

1(1) (2) (2) (1)L U L UK d dr

(LUMO) (HOMO) (LUMO) (HOMO)

ü  Donor-‐Acceptor backbone ü  X:Introduc6on of steric hindrance

Donor Acceptor X

・Large ΔEST

µ = φL(∫∫ 1)φU (2)r 12φL(2)φU (1)dτ1dτ 2ｆ ∝µ2

Small:ΔEST

Moderate Oscillator Strength:f

Molecular Design

Moderate radiative decay rate with small ΔEST

Transition dipole moment

HOMO

LUMO 5

Molecular design for efficient TADF

Al LiF

6wt% 4CzTPN/CBP α-NPD

ITO/Glass

TPBi

Very high efficiency TADF based OLED (Internal QE~100%)

10-3 10-2 10-1 100 101 10210-2

10-1

100

101

Exte

rnal

EL

quan

tum

effi

cien

cy (%

)

Current density (mA/cm2)

4CzIPN 4CzTPN-Ph 2CzPN

400 500 600 700

2CzPN 4CzIPN 4CzPN 4CzTPN 4CzTPN-Me 4CzTPN-Ph

Nor

mal

ized

PL

inte

nsity

Wavelength (nm)

EQE~20% (Internal QE: approaching to 100%)

Phthalonitrile deriva6ves

T. Uoyama et al., Nature, 492, 234 (2012)

HOMO LUMO

DFT (M06-2X/6-31G(d)) PLQY~95%

6

Internal QE nearly 100% blue OLED

EQE20%

Q. Zhang, et al., Nature Photonics, 8, 326 (2014) 7

Internal QE nearly 100% Blue OLED

Phenazine (PPZ)

Acridine (DMAC)

Phenoxazine (PXZ) Phenazine (PPZ)

Oxadiazole (DPO) Triazole (TPT)

Diphenyl sulfone (DPS)

B3LYP/6-‐31G* level

DMAC-DPS λ~460nm

DMAC-DPS τ~3µs

Phenazine (PPZ)

3LE=2.4eV

Phenoxazine (PXZ)

3LE=2.7eV

Acridine (DMAC)

3LE=3.0eV

ΔEST=0.08eV PLQY~90% λmax=465nm

8

High efficiency blue TADF: Optimization of donor and acceptor units

EQE 17.5 ± 1.5%, λEL~610nm CIE (0.60, 0.40)

J. Li, T. Nakagawa, J. MacDonald, Q. Zhang, H. Nomura, H. Miyazaki, and C. Adachi (CSIRO and Kyushu Univ.)

PL EL

Melem

Adv. Mat., 25, 3319 (2013)

S1-T1 transition is an optically hidden process!

9

Red TADF

4CzIPN ⊿EST：0.01.eV λ max：513nm

EQE:19%

4CzPN ⊿EST：0.12.eV λ max：531nm

EQE ：18%

4CzTPN ⊿EST：0.06.eV λ max：544nm

EQE：17%

Nature, 492, 234 (2012)

HAP-3TPA ⊿EST：0.17.eV λ max：610nm EQE：17.5%

Adv. Mat.,25, 3319 (2013)

Spiro-CN ⊿EST：0.06eV λ max：540nm

EQE：4.4% Chem. Com.,

48, 9580 (2012)

DMAC-DPS ⊿EST：0.08eV λ max：465nm

EQE：20%

Nat. Photo. 8, 326 (2014)

ACRFLCN ⊿EST：0.10eV λ max：485nm

EQE：10%

Spiro-AN ⊿EST：0.025eV λ max：495nm EQE：16.5% Chem. Comm.

49, 10385 (2013)

a)

Angew. Chem. 2012, 51, 11311

⊿EST：0.1eV λ max：466nm

EQE：5.3%

PIC-TRZ2 ⊿EST：0.01eV λ max：505nm

EQE：14% Phys. Rev. Lett.

110, 247401 (2013)

PXZ-TRZ ⊿EST：0.0084.eV λ max：522nm EQE：15.5%

CC2TA ⊿EST：0.07eV λ max：493nm

EQE：11% Appl. Phys. Lett., 98, 83302 (2011)

Appl. Phys. Lett., 101, 93306 (2012)

Chem. Com., 48, 11392 (2012)

PIC-TRZ

Melem

Sulphone

Molecular Design ü  SeparaGon of HOMO and LUMO, but rather gentle decrease of HOMO and

LUMO distribuGon for large transiGon dipole moment. ü  Use of donor/acceptor units having a high localized triplet state (3LE) ü  Small ΔEST for short transient Gme ~µs order

10

Molecular Design for TADF

²  High color purity (narrow spectrum) ²  Long lifetimes of operational stability ²  Unlimited molecular design ²  Theoretical limitation of ηr

25% - 62.5% (even TTA process)

Fluorescence based OLEDs

TADF based OLEDs²  High efficiency up to 100% ²  Unlimited molecular design ²  Broad spectra due to CT emission (not appropriate for display applications)

H. Nakanotani, et al., Nature Comm. 5, 4016 (2014)

²  Long life6mes of opera6onal stability ²  High color purity ²  Flexibility of material design ²  Theore6cal limita6on of ηr-‐ 100 %

TADF as assistant & Fluorescence as emitter

Fusion of two

Func6ons

TADF: Exciton-‐

genera6on

Fluo: Light-

emission

400 500 600 700

2CzPN 4CzIPN 4CzPN 4CzTPN 4CzTPN-Me 4CzTPN-Ph

Nor

mal

ized

PL

inte

nsity

Wavelength (nm)

T1

T1

S0

S1

S0

1/8

3/8 S0

3M*

4/8

3M*

Interamolecular: T. Uoyama et al., Nature, 492, 234 (2012) Intermolecular: K. Goushi et al., Nature Photo. 6, 253 (2012)

11

A new route to harvest triplets in OLEDs with fluorescence emitters

² Minimizing concentra6on quenching of TADF molecules ²  Efficient FRET but no Dexter transfer

RISC

FRET

S1 T1

h+ e-

25% 75%

Host Assistant dopant DBP

T1S1

Exciton formationa

TBPe TTPA TBRb

b c

d e

TBPe

ACRSA

TTPA

ACRXTN

TBRb

PXZ-TRZ

DBP

tri-PXZ-TRZ

N

O

ON

O

NON

NN

NON

NN

N

N

O

OACRSA ACRXTN PXZ-TRZ tri-PXZ-TRZ

Assisting dopantTADF (10-‐20%) Fluorescence emiher (~1%)

S1

T1 X Exciton forma6on

12

TADF as assistant dopant and Fluorescence as emitter in host layer

H. Nakanotani, et al, Nat. Commun., 5, 4016, 2014

13

Large chance of FRET and small chance for Dexter between TADF and Fluo.

100 101 102 103 1040

2

4

6

8

10

12

14

16

18

20

Ex

tern

al E

L qu

antu

m e

ffici

ency

(%)

Luminance (cd/m2)4

Flu. TADF (PXZ-TRZ)

Assistant dopant (TADF)+Fluorescence dopant

TADF emitter

Fluorescence emitter

● 1wt%-‐TBRb:25wt%-‐PXZTRZ:mCBP

● 1wt%-TBRb:mCBP

● 25wt%-PXZTRZ:mCBP

Addition of TADF

14

Improved OLED architecture with double doped emitter layer

a b

c d

N N

e

a b

c d

N N

e

EQE 18.0% EQE 17.5%

EQE 15.8% EQE 13.4%

w/o TADF

w/o TADF w/o TADF

w/o TADF (b)

TBPe

ACRSA

TTPA

ACRXTN

TBRb

PXZ-TRZ

DBP

tri-PXZ-TRZ

N

O

ON

O

NON

NN

NON

NN

N

N

O


TADF molecules(a)

(b)

TBPe

ACRSA

TTPA

ACRXTN

TBRb

PXZ-TRZ

DBP

tri-PXZ-TRZ

N

O

ON

O

NON

NN

NON

NN

N

N

O


TADF molecules(a)

(b)

TBPe

ACRSA

TTPA

ACRXTN

TBRb

PXZ-TRZ

DBP

tri-PXZ-TRZ

N

O

ON

O

NON

NN

NON

NN

N

N

O


TADF molecules(a)

(b)

TBPe

ACRSA

TTPA

ACRXTN

TBRb

PXZ-TRZ

DBP

tri-PXZ-TRZ

N

O

ON

O

NON

NN

NON

NN

N

N

O


TADF molecules(a)

15

Improved OLED architecture with various emission colors

H. Nakanotani, et al, Nat. Commun., 5, 4016, 2014

-6.2

-5.8

-5.4

-5.0

-4.6

-4.2

-3.8

-3.4

-3.0

-2.6

-2.2 DMACDPSmCP

DBPTTPA

Energy transfer (ET)

Recombination site(Blue TADF donor)

Spacer (EBL)

Acceptor

a

b

c

ET

SO O

N N

N N

Energy donor (TADF)

Energy acceptors (Fluo.)

DMAC-‐‑‒DPS

TTPA

DBPspacer prohibits

Dextor transfer 16

W-‐OLED: Spa6ally separa6on of D-‐A layer

T. Higuchi, H. Nakanotani, C. Adachi (Adv. Mat. in press)

DMACDPS

DBPTTPA

DMACDPS

Device A(EQE=16%)

Device B(EQE=2%)

DBPTTPA

Energy transfer (ET)

ET

DMACDPS

Device C(EQE=13%)

17

Spa6ally separa6on of D-‐A layer

T. Higuchi, H. Nakanotani, C. Adachi (submitted to Adv. Mat.)

18

"Promising opera6onal stability of high-‐efficiency organic light-‐emijng diodes based on thermally ac6vated delayed fluorescence"

Scien6fic Reports, 3, 2127 (2013)) H. Nakanotani, K. Masui, J. Nishide, T. Shibata and C. Adachi

c

Time (hr)

Scientific Reports, 3, 2127 (2013)

In op6mized OLED, projected half life6me LT50 is ~10,000hrs.

ITO/HAT-‐CN/TrisPCz/4CzIPN:mCBP/T2T/BPyTP2/LiF/Al

19

Improved OLED reliability with 4CzIPN deriva6ves

Scien6fic Reports, 3, 2127 (2013)

HAT-CN [10]

Tris-PCz [30]

4CzIPN

mCBP [30]

ITO

-9.5

5.5

6.0

5.6

2.1

5.8

3.4

2.4

Tris-PCz [50]

5.6

2.1

Au

+ + + +

×

Hole only devices No change in J-‐V characteris[cs

Electron only devices Significant improvement of J-‐V with increase of 4CzIPN conc.

4CzIPN

mCBP [30]

T2T[10]

BPy-TP2[80]

ITO

LiF/Al

6.0

5.8

3.4

2.4

3.0

6.5

5.7

2.7

T2T[30]

3.0

6.5

- - -

×

-

20

Degrada6on mechanism: J-‐V in HOD and EOD with different 4CzIPN conc.


HAT-CN

Tris-PCz

4CzIPN

mCBP

T2T

BPy-TP2ITO

LiF/Al

-9.5

5.5

6.0

5.6

2.1

5.8

3.4

2.43.0

6.5

5.7

2.7

+

-

HAT-CN

Tris-PCz

4CzIPN

mCBP

T2T

BPy-TP2ITO

LiF/Al

-9.5

5.5

6.0

5.6

2.1

5.8

3.4

2.43.0

6.5

5.7

2.7

+

-

ü  Low dopant concentra6on inhibits electron injec6on from T2T into EML ü  Higher dopant concentra6on facilitates electron injec6on, resulted in

expansion of carrier recombina6on region into EML

3〜6wt% >6wt%


21

Degrada6on mechanism: charge accumula6on at T2T/EML interface

a

b

c

4CzIPN-MeTBRb +4CzIPN-MeTADF＋Fluo.

4,000hr TADF 1,500hr

22

Hyperfluorescence :Enhancement of device reliability (> x2.5)

TADF

Fluo

Features-‐‑‒Exciton generation via TADF (assistant dopant with fluorescent material performing the light-‐‑‒emitting function)·∙ Achieves high efficiency light-‐‑‒emission with fluorescent material Fluorescent materials provide a high-‐‑‒purity light emission color.·∙ TADF is prevented from rapid deterioration due to the emission process by performing only exciton generation

EffectHigh efficiency, high quality emission & long life can be achieved through combination of the properties of TADF and fluorescent materials.

Superior, high-‐‑‒purity emission color(Using the features of fluorescent materials) Decreasing TADF Degradation

Solu6on: Assisted Hyperfluorescence with TADF

Market

CollaboraTons with materials & panel manufacturers to opTmize devices are the key to rapid commercializaTon

Ways to Rapid Commercializa6on by Achieving Long Life Time

Combination of Materials

Thickness of Each Layer

Hole Injection Layer (HIL)

Glass Substrate

Hole Transport Layer (HTL)

Emitting Layer (EML) •  Host •  TADF: Assistant Dopant •  Fluo.: emitting Dopant

Electron Transport Layer (ETL)

Cathode (Metals)

Anode （ITO）

Electron Injection Layer (EIL)

ー

＋

＋

ー

Emission

A startup company has been established for

TADF commercialization

24

 

 

 

 

Summary

² Small ΔEST realized 100% upconversion from T1 to S1, resultedin 100% delayed fluorescence.

² Assistant dopant system realized 100% IQE from fluorescencemolecules.

² Device lifeQme is significantly enhanced by opQmizingperipheral materials.

² Rapid upconversion shorter τT→S less than 1µs will be expectedfor further development of high performance TADF and lasers.

S1

S0

FRET

TADF Fluorescence

RISC 600 700 Wavelength (nm)

400 500

T1

25% 75%

25

Acknowledgement n OPERA Research Team in Kyushu Univ. and collaborators JST ERATO

2010-‐2014 2014-‐2019 This work was supported by Funding Program for World-‐Leading

InnovaQon R&D on Science and Technology (FIRST), WPI and JST ERATO.

・Supervisors Prof. T. YasudaProf. K. Goushi

・SnF2OEP 　A. Endo, A. Takahashi

・PIC-‐TRZ, PIC-‐TRZ2　K. Sato, H. Miyazaki, K. Yoshimura, A. Kawada

・Cz-‐TRZ 　SY. Lee, S. Hirata

・PXZ-‐TRZ 　H. Tanaka. K. Shizu, J. Lee

・HAP-‐3TPA 　Jie Li, T. Nakagawa, James MacDonald,K. Ueno (CSIRO), Q. Zhang, H. Nomura

・Phthalonitrile 　T. Uoyama, K. Shizu, H. Nomura

・4CzIPN (Reliability)　H. Nakanotani, K. Masui,

J. Nishida, T. Shibata

・Anthraquinones 　Q. Zhang, H. Kuwabara

・Blue TADF Q. Zhang, BoLi

・Double doping of TADF and Fluo. 　H. Nakanotani, T. Higuchi, T. Furukawa

・Special thanks to collaborators Profs. Kaji (Kyoto U), Murata (JAIST), Ishii (Chiba U),Orita (Okayama U), Takimiya (Hiroshima U), Naito (Osaka Pref. U.), Matsumoto (Osaka City U.), Ueda (Kobe U),Mizuno (Waseda U.), Sato (Nagaoka), Kawai (NAIST),Ueno (CSIRO)

JDI, TEL, Panasonic, Mitsbishi Ryon, Tokai Rubber, Hirata, Daiden,Toshiba, Hodogaya Chemical, NSCC, Nippon Kayaku

26

junji adachi, kyushu university

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