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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
OACRSA ACRXTN PXZ-TRZ tri-PXZ-TRZ
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
OACRSA ACRXTN PXZ-TRZ tri-PXZ-TRZ
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
OACRSA ACRXTN PXZ-TRZ tri-PXZ-TRZ
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
OACRSA ACRXTN PXZ-TRZ tri-PXZ-TRZ
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.
Scien6fic Reports, 3, 2127 (2013)
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%
Scien6fic Reports, 3, 2127 (2013)
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