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Phosphorescent OLEDs
Jeffrey LipshultzMacMillan Lab Group Meeting
November 1, 2017
What is an Organic LED?
Three basic components:
1. Anode: inject holes (i.e. positive charges)2. Organic seminconductor Emission Layer (EML)3. Cathode: inject electrons
How does it work?
Zysman-Colman, E. Iridium(III) in Optoelectronic and Photonics Applications; John Wiley & Sons Ltd: Hoboken, NJ, 2017.Hartmut, Y. Highly Efficient OLEDs with Phosphorescent Materials; Wiley-VCH: Weinheim, 2008.
Early OLEDs
Tang, C. W.; VanSlyke, S. A. Appl. Phys. Lett. 1987, 51, 913.Burroughes, J. H. et. al. Nature 1990, 347, 539.
1987: First “practical” (> 1% EQE) OLED using Alq3 (Eastman Kodak)
Alq3
N
OAl
3
“diamine”
N Np-tol
p-tol
p-tol
p-tol
External Quantum Efficiency (EQE) Internal Quantum Efficiency (IQE)
electrons injectedphotons emitted
excitons producedphotons emitted
!ex = !i =
Early OLEDs
Tang, C. W.; VanSlyke, S. A. Appl. Phys. Lett. 1987, 51, 913.Burroughes, J. H. et. al. Nature 1990, 347, 539.
1987: First “practical” (> 1% EQE) OLED using Alq3 (Eastman Kodak)
1990: First polymer-based OLED (~ 8% EQE) using PPV (Burroughes, Cambridge)
PPV
Alq3
N
OAl
3
n
“diamine”
N Np-tol
p-tol
p-tol
p-tol
Fluorescent OLEDs: Limitations
Baldo, M. A.; O’Brien, D. F.; Thompson, M. E.; Forrest, S. R. Phys. Rev. B. 1999, 60, 14422.
1987: First “practical” (> 1% EQE) OLED using Alq3 (Eastman Kodak)
Alq3
N
OAl
3
Why only 1% EQE?
poor SOC means no emission from T1
BUT
spin statistics dictate that excitons formedin 1:3 singlet:triplet ratio,
somewhat verified experimentally
~25% IQEtheoretical limit
!s = (20±1)%
1990: First polymer-based OLED (~ 8% EQE) using PPV (Burroughes, Cambridge)
PPV
n
!s = (20±4)%
Segal, M.; Baldo, M. A.; Holmes, R. J.; Forrest, S. R.; Soos, Z. G. Phys. Rev. B. 2003, 68, 075211.
If
Phosphorescent OLEDs
The basics of PhOLEDs
Fluorescence vs. Phosphorescence
Basic design concept
PhOLED architectures and materials
Multi-layered devices
Phosphorescent emitters
Small-molecule and polymer hosts
Current state-of-the-art
Blue emitters!
WOLEDs via mixed fluorescence/phosphorescence
Thermally-activated delayed phosphorescence (TADF)
Exciton formation/transfer
What makes a good dopant and host?
Specific considerations
Fluorescence vs. Phosphorescence
Jablonski diagram upon photoexcitation
S0
S1T1
abs
fluor
esce
nce
inte
rnal
con
vers
ion
ISC
phos
phor
esce
nce
alt-I
SC
Jablonski diagram upon electroexcitation
S0
S1T1
excit
on fo
rmat
ion
fluor
esce
nce
inte
rnal
con
vers
ion
ISC
phos
phor
esce
nce
alt-I
SC
excit
on fo
rmat
ion
1. Efficient exciton-harvesting requires (?) triplet-harvesting
Key points for OLED development:
2. EL from T1 requires appreciable SOC3. T1 lifetime much longer than S1
4. E(T1) < E(S1)
Basic Design of PhOLEDs
Minaev, B.; Baryshnikov, G.; Agren, H. Phys. Chem. Chem. Phys. 2014, 16, 179.
Host/guest or host/dopant EML
1998: First phosphor-doped OLED (Forrest, Princeton)
Baldo, M. A.; O’Brien, D. F.; You, Y.; Shoudtikov, A.; Sibley, S.; Thompson, M. E.; Forrest, S. R. Nature 1998, 395, 151.
N
N N
N
Et
Et
Et
Et Et
Et
Et
Et
Pt
PtOEP
anod
e
cath
ode
host
dopant
S1 T1
Alq3
N
OAl
3
peak efficiencies:!ex = 4%!i = 23%
EL lifetime 10-50 "s
Basic Principles of PhOLEDs
Hartmut, Y. Highly Efficient OLEDs with Phosphorescent Materials; Wiley-VCH: Weinheim, 2008.
Hole/electron recombination, aka exciton formation
Segal, M.; Singh, M.; Rivoire, K.; Difley, S.; Van Coorhis, T.; Baldo, M. A. Nature Mater. 2007, 6, 374.
anod
e
cath
ode
host
dopant
S1 T1
As hole and electron get closer, Coloumbic attractions come into play
ΔE(e-h) =e2
4!ℇ0ℇRC= kBT RC(300 K) ≈ 180 Å
These associated h+ and e- are called a charge transfer (CT) state.
They don’t necessarily need to be on a single molecule or polymer chain.
Basic Principles of PhOLEDs
Hartmut, Y. Highly Efficient OLEDs with Phosphorescent Materials; Wiley-VCH: Weinheim, 2008.
Hole/electron recombination, aka exciton formation
Reineke, S.; Baldo, M. A. Phys. Status Solidi A 2012, 209, 2341.
anod
e
cath
ode
host
dopant
S1 T1
Four main scenarios for exciton formation:
Sn formation in host
Tn formation in host
Sn formation in dopant
Tn formation in dopant
exciton in host exciton in dopant
Förster ET
Dexter ET
ISCISC
Basic Principles of PhOLEDs
Hartmut, Y. Highly Efficient OLEDs with Phosphorescent Materials; Wiley-VCH: Weinheim, 2008.
Host exciton energy transfer to dopant exciton, ISC/relaxation, phosphorescence
Yersin, H. Top. Curr. Chem. 2004, 241, 1.
Basic Principles of PhOLEDs
Hartmut, Y. Highly Efficient OLEDs with Phosphorescent Materials; Wiley-VCH: Weinheim, 2008.
Exciton formation on the dopant: hole trapping first
Yersin, H. Top. Curr. Chem. 2004, 241, 1.
Basic Principles of PhOLEDs
Tao, Y.; Yang, C.; Qin, J. Chem. Soc. Rev. 2011, 40, 2943.
characteristics of good PhOLED host
Kappaun, S.; Slugove, C.; List, E. J. W. Int. J. Mol. Sci. 2008, 9, 1527.
1. Large HOMO-LUMO gap (high energy LUMO)
2. Long T1 lifetime = non-phosphorescent = poor SOC
3. Higher energy S1, T1 than dopant
4. Can efficiently transfer h+ or e-, or both (ambipolar)
5. Spectral overlap (for FRET) and energy overlap (for DET)
1. Lower LUMO than host
2. Shorter T1 lifetime = phosphorescent = good SOC
3. Lower energy S1, T1 than host
4. Can efficiently trap h+ or e-, or both
5. Spectral overlap (for FRET) and energy overlap (for DET)
characteristics of good PhOLED dopant/emitter
Phosphorescent OLEDs
The basics of PhOLEDs
Fluorescence vs. Phosphorescence
Basic design concept
PhOLED architectures and materials
Multi-layered devices
Phosphorescent emitters
Small-molecule and polymer hosts
Current state-of-the-art
Blue emitters!
WOLEDs via mixed fluorescence/phosphorescence
Thermally-activated delayed phosphorescence (TADF)
Exciton formation/transfer
What makes a good dopant and host?
Specific considerations
Mulitlayer OLED Device
Minaev, B.; Baryshnikov, G.; Agren, H. Phys. Chem. Chem. Phys. 2014, 16, 179.
representative multilayer PhOLED
Kappaun, S.; Slugove, C.; List, E. J. W. Int. J. Mol. Sci. 2008, 9, 1527.
glass substrateanode
hole-injection layer (HIL)
hole-transport layer (HTL)
host/guest
hole-blocker layer (HBL)
electron-transport layer (ETL)
electron-injection layer (EIL)
cathode
emission layer (EML)
examples
Al, Mg/Ag, metals
CsF, LiF
most common: Alq3
bathocuproine (BCP)
to be discussed in detail
bis(N,N’-diaryl)-biphenyls
PEDOT:PSS, [M]OnITO
characteristics/roles
… to be a cathode
high LUMO
high ETelectron-deficient (pyridines)
prevent “unused” h+from destroying ETL
transport h+/e– to form excitons
high ETelectron-rich (triarylamines)
low HOMOITO
Triplet-Emitting Dopants (Phosphors)
Nazeeruddin, M. K., et al. Top. Curr. Chem. 2017, 375, 39.
Heavy-metal organometallic complexes exhibit appropriate phosphorescence
N
N N
N
Et
Et
Et
Et Et
Et
Et
Et
Pt
PtOEP
T1 lifetime = 91 !sλmax = 650 nm
IrIII
N
N N
Ir(ppy)3
T1 lifetime = 2.1 !sλmax = 509 nm
Ir(ppy)2(acac)
T1 lifetime = 1.6 !sλmax = 516 nm
IrIII
N
N
O
OMe
Me
IrIII
N
N
OO
N
F
F
FIrpic
T1 lifetime = 1.7 !sλmax = 468 nm
Hartmut, Y. Highly Efficient OLEDs with Phosphorescent Materials; Wiley-VCH: Weinheim, 2008.
Chou, P.-T.; Chi, Y. Chem. Eur. J. 2007, 13, 380.
really long lifetimehigh concentration of T1triplet-triplet annihilation
F
F
Triplet-Emitting Dopants (Phosphors)
Nazeeruddin, M. K., et al. Top. Curr. Chem. 2017, 375, 39.
Heavy-metal organometallic complexes exhibit appropriate phosphorescence
Ir(piq)3
T1 lifetime = 0.7 !sλmax = 620 nm
IrIII
N
N N
Ir(ppy)3
T1 lifetime = 2.1 !sλmax = 509 nm
Ir(ppy)2(acac)
T1 lifetime = 1.6 !sλmax = 516 nm
IrIII
N
N
O
OMe
Me
FIrpic
T1 lifetime = 1.7 !sλmax = 468 nm
Hartmut, Y. Highly Efficient OLEDs with Phosphorescent Materials; Wiley-VCH: Weinheim, 2008.
Chou, P.-T.; Chi, Y. Chem. Eur. J. 2007, 13, 380.
IrIII
N
N N
IrIII
N
N
OO
N
F
F
F
F
Host Materials for PhOLEDs
Tao, Y.; Yang, C.; Qin, J. Chem. Soc. Rev. 2011, 40, 2943.Segal, M.; Singh, M.; Rivoire, K.; Difley, S.; Van Coorhis, T.; Baldo, M. A. Nature Mater. 2007, 6, 374.
Hole-transport-type hosts(electron-rich aromatic systems)
Electron-transport-type hosts(electron-deficient aromatic systems)
Ambipolar hosts(donor-acceptor systems)
anode
cathode
HIL
EIL
EML
*
anode
cathode
HIL
EIL
EML
*
anode
cathode
HIL
EIL
EML*
Type of host material determines exciton-generation zone
Host Materials for PhOLEDs
Tao, Y.; Yang, C.; Qin, J. Chem. Soc. Rev. 2011, 40, 2943.Segal, M.; Singh, M.; Rivoire, K.; Difley, S.; Van Coorhis, T.; Baldo, M. A. Nature Mater. 2007, 6, 374.
Hole-transport-type hosts(electron-rich aromatic systems)
Electron-transport-type hosts(electron-deficient aromatic systems)
Ambipolar hosts(donor-acceptor systems)
N
N 2
CBP
NnPVK
NN
N
TAZ
N
N
NPh
Ph
Ph
T2T
P
P 2
PO1
PhPh
OPh
O
Ph
TFTPA
N
O
N
R
Nalk
CzOXD
N N
Ph Ph
RN
m-CZBP
N
P(O)Ph2Ph2(O)P
PPO2NAr
Ar Ph
Dopant Concentration Effect
Reineke, S.; Baldo, M. A. Phys. Status Solidi A 2012, 209, 2341.Adachi, C. et al. Appl. Phys. Lett. 2005, 86, 071104.
high concentration of dopant leads to dimished efficiency“concentration quenching”
triplet-triplet annihilation
Förster-type
Staroske, W.; Pfeiffer, M.; Leo, K.; Hoffmann, M. Phys. Rev. Lett. 2007, 98, 197402.
case study: Ir(ppy)3 in CBP
RF = 2.9 nm
Dexter-type
Dopant Concentration Effect
Reineke, S.; Baldo, M. A. Phys. Status Solidi A 2012, 209, 2341.Adachi, C. et al. Appl. Phys. Lett. 2005, 86, 071104.
high concentration of dopant leads to dimished efficiency“concentration quenching”
triplet-triplet annihilation
Staroske, W.; Pfeiffer, M.; Leo, K.; Hoffmann, M. Phys. Rev. Lett. 2007, 98, 197402.
case study: Ir(ppy)3 in CBP
RF = 2.9 nm
0.1% Ir(ppy)3in TCTA
Increased IQE by Exciton Confinement
Adachi, C.; Baldo, M. A.; Forrest, S R.; Thompson, M. E. Appl. Phys. Lett. 2000, 77, 904.Adachi, C.; Baldo, M. A.; Thompson, M. E.; Forrest, S R. J. Appl. Phys. 2001, 90, 5048.
N N
NPh Ph
host: TAZ dopant: Ir(ppy)2(acac)HTL: HMTPD ETL: Alq3
N
OAl
3
N
MeMe
Me
2
emission from HMTPD likely indicates exciton formation in HTL
poor hole injection to EML/poor recombination in EML
HOMO of host is below HOMO of HTL, unfavorable hole injection
IrIII
N
N
O
OMe
Me
12% Ir(ppy)2(acac)
!ext = (19±0.5)%
!i = (87±7)%
Increased IQE by Exciton Confinement
Adachi, C.; Baldo, M. A.; Forrest, S R.; Thompson, M. E. Appl. Phys. Lett. 2000, 77, 904.Adachi, C.; Baldo, M. A.; Thompson, M. E.; Forrest, S R. J. Appl. Phys. 2001, 90, 5048.
N N
NPh Ph
host: TAZ dopant: Ir(ppy)2(acac)HTL: HMTPD ETL: Alq3
N
OAl
3
N
MeMe
Me
2
emission from HMTPD likely indicates exciton formation in HTL
poor hole injection to EML/poor recombination in EML
HOMO of host is below HOMO of HTL, unfavorable hole injection
IrIII
N
N
O
OMe
Me
12% Ir(ppy)2(acac)
!ext = (19±0.5)%
!i = (87±7)%
Increased IQE by Exciton Confinement
Adachi, C.; Baldo, M. A.; Forrest, S R.; Thompson, M. E. Appl. Phys. Lett. 2000, 77, 904.Adachi, C.; Baldo, M. A.; Thompson, M. E.; Forrest, S R. J. Appl. Phys. 2001, 90, 5048.
N N
NPh Ph
host: TAZ dopant: Ir(ppy)2(acac)HTL: HMTPD ETL: Alq3
N
OAl
3
N
MeMe
Me
2
emission from HMTPD likely indicates exciton formation in HTL
poor hole injection to EML/poor recombination in EML
HOMO of host is below HOMO of HTL, unfavorable hole injection
IrIII
N
N
O
OMe
Me
12% Ir(ppy)2(acac)
!ext = (19±0.5)%
!i = (87±7)%
Phosphorescent OLEDs
The basics of PhOLEDs
Fluorescence vs. Phosphorescence
Basic design concept
PhOLED architectures and materials
Multi-layered devices
Phosphorescent emitters
Small-molecule and polymer hosts
Current state-of-the-art
Blue emitters!
WOLEDs via mixed fluorescence/phosphorescence
Thermally-activated delayed phosphorescence (TADF)
Exciton formation/transfer
What makes a good dopant and host?
Specific considerations
E(T1) FIrpic > E(T1) CBPbut
kR >> kh
uphill ET can occurto repopulate T1 of FIrpic
leading to delayed/prolongedphosphorescence!
“Endothermic Energy Transfer” for Phosphorescence
Adachi, C.; Kwong, R. C.; Djurovich, P.; Adamovich, V.; Baldo, M. A.; Thompson, M. E.; Forrest, S R. Appl. Phys. Lett. 2001, 79, 2082.Adachi, C.; Baldo, M. A.; Thompson, M. E.; Forrest, S R. J. Appl. Phys. 2001, 90, 5048.
host: CBP dopant: FIrpicHTL: NPD ETL: Alq3
N
OAl
3
N
2
N
2
IrIII
N
N
OO
N
F
F
F
F
up to 10 ms lifetimeof phosphorescence no CBP phosphorescence observed
FIrpic phosphorescence observedat both early and delayed times
!ext = (5.7±0.3)%
“Endothermic Energy Transfer” for Phosphorescence
Adachi, C.; Kwong, R. C.; Djurovich, P.; Adamovich, V.; Baldo, M. A.; Thompson, M. E.; Forrest, S R. Appl. Phys. Lett. 2001, 79, 2082.Adachi, C.; Baldo, M. A.; Thompson, M. E.; Forrest, S R. J. Appl. Phys. 2001, 90, 5048.
host: CBP dopant: FIrpicHTL: NPD ETL: Alq3
N
OAl
3
N
2
N
2
IrIII
N
N
OO
N
F
F
F
F
Improved Efficiency in Blue Phosphorescent LEDs
Adachi, C.; Kwong, R. C.; Djurovich, P.; Adamovich, V.; Baldo, M. A.; Thompson, M. E.; Forrest, S R. Appl. Phys. Lett. 2001, 79, 2082.Tokito, S.; Ijima, T.; Suzuri, Y.; Kita, H.; Tsuzuki, T.; Sato, F. Appl. Phys. Lett. 2003, 83, 569.
host: CBP dopant: FIrpicHTL: NPD ETL: Alq3
N
OAl
3
N
2
N
2
host: CDBP dopant: FIrpicHTL: NPD ETL: Alq3
N
OAl
3
N
2
N
2
Me
!ext = (5.7±0.3)%
!ext = 10.4%
IrIII
N
N
OO
N
F
F
F
F
IrIII
N
N
OO
N
F
F
F
F
Improved Efficiency in Blue Phosphorescent LEDs
Adachi, C.; Kwong, R. C.; Djurovich, P.; Adamovich, V.; Baldo, M. A.; Thompson, M. E.; Forrest, S R. Appl. Phys. Lett. 2001, 79, 2082.Tokito, S.; Ijima, T.; Suzuri, Y.; Kita, H.; Tsuzuki, T.; Sato, F. Appl. Phys. Lett. 2003, 83, 569.
host: CBP
N
2
host: CDBP
N
2
Me
!ext = (5.7±0.3)%
!ext = 10.4%
E(T1) = 2.6 eV
E(T1) = 3.0 eV
dopant: FIrpic
phosphorescence decays significantly faster
exothermic ET to phosphor is more efficient than endothermic
IrIII
N
N
OO
N
F
F
F
F
Improved Efficiency in Blue Phosphorescent LEDs
Adachi, C.; Kwong, R. C.; Djurovich, P.; Adamovich, V.; Baldo, M. A.; Thompson, M. E.; Forrest, S R. Appl. Phys. Lett. 2001, 79, 2082.Tokito, S.; Ijima, T.; Suzuri, Y.; Kita, H.; Tsuzuki, T.; Sato, F. Appl. Phys. Lett. 2003, 83, 569.
host: CBP
N
2
host: CDBP
N
2
Me
!ext = (5.7±0.3)%
!ext = 10.4%
E(T1) = 2.6 eV
E(T1) = 3.0 eV
dopant: FIrpic
phosphorescence decays significantly faster
exothermic ET to phosphor is more efficient than endothermic
IrIII
N
N
OO
N
F
F
F
F
Improving Stability and Lifetime of Blue PhOLEDs
Seifert, R.; Rabelo de Moraes, I.; Scholz, S.; Gather, M. C.; Lussem, B.; Leo, K. Org. Electron. 2013, 14, 115.Endo, A.; Suzuki, K.; Yoshihara, T.; Tobita, S.; Yahiro, M.; Adachi, C. Chem. Phys. Lett. 2008, 460, 155.
FIrpic
T1 lifetime = 1.2 !sλmax = 476 nm
IrIII
N
N
N
N
F
F
T1 lifetime = 2.2 !sλmax = 458 nm
FIr6
as films in mCP
N N
N
NB
N
N
N
N
high triplet energy emittersrapid decay of pure films and OLED devicesstabilization with improved hosts, HBL, etc
IrIII
N
N
OO
N
F
F
F
F
F
F
Improving Stability and Lifetime of Blue PhOLEDs
Seifert, R.; Rabelo de Moraes, I.; Scholz, S.; Gather, M. C.; Lussem, B.; Leo, K. Org. Electron. 2013, 14, 115.Zhang, Y.; Lee, J.; Forrest, S. R. Nat. Commun. 2014, 5, 5008.
Ir(dmp)3λmax = 466 nm
IrIIINN
MeMe
3
NN
mCBP
E(HOMO) = 5.0 eV E(HOMO) = 6.0 eVhole transport in EML electron transport in EML
at high Ir(dmp)3 concentrations, exciton formation should occur
only in vicinty of/on Ir(dmp)3
anode
Improving Stability and Lifetime of Blue PhOLEDs
Seifert, R.; Rabelo de Moraes, I.; Scholz, S.; Gather, M. C.; Lussem, B.; Leo, K. Org. Electron. 2013, 14, 115.Zhang, Y.; Lee, J.; Forrest, S. R. Nat. Commun. 2014, 5, 5008.
Ir(dmp)3λmax = 466 nm
IrIIINN
MeMe
3
NN
mCBP
E(HOMO) = 5.0 eV E(HOMO) = 6.0 eVhole transport in EML electron transport in EML
at high Ir(dmp)3 concentrations, exciton formation should occur
only in vicinty of/on Ir(dmp)3
!ext= (8.5±0.1)%T50 = 510 h
!ext = (9.5±0.1)%T50 = 1500-1600 h
anode
Improving Stability and Lifetime of Blue PhOLEDs
Seifert, R.; Rabelo de Moraes, I.; Scholz, S.; Gather, M. C.; Lussem, B.; Leo, K. Org. Electron. 2013, 14, 115.Zhang, Y.; Lee, J.; Forrest, S. R. Nat. Commun. 2014, 5, 5008.
Ir(dmp)3λmax = 466 nm
IrIIINN
MeMe
3
NN
mCBP
E(HOMO) = 5.0 eV E(HOMO) = 6.0 eVhole transport in EML electron transport in EML
at high Ir(dmp)3 concentrations, exciton formation should occur
only in vicinty of/on Ir(dmp)3
!ext = (9.5±0.1)%T50 = 1500-1600 h
!ext = (18±0.2)%T50 = 3500-3700 h
Improving Stability and Lifetime of Blue PhOLEDs
Sarma, M.; Tsai, W.-L.; Lee, W.-K.; Chi, Y.; Wu, C.-C.; Liu, S.-H.; Chou, P.-T.; Wong, K.-T. Chem 2017, 3, 461.
FIrpic
T1 lifetime = 1.1 !sλmax = 470 nm
MS2
T1 lifetime = 0.8 !sλmax = 475 nm
IrIII
N
N
OO
N
F
F
F
F IrIII
N
N
N
N
OO
N
F
F
F
F
Improving Stability and Lifetime of Blue PhOLEDs
Sarma, M.; Tsai, W.-L.; Lee, W.-K.; Chi, Y.; Wu, C.-C.; Liu, S.-H.; Chou, P.-T.; Wong, K.-T. Chem 2017, 3, 461.
FIrpic
T1 lifetime = 1.1 !sλmax = 470 nm
MS2
T1 lifetime = 0.8 !sλmax = 475 nm
IrIII
N
N
OO
N
F
F
F
F IrIII
N
N
N
N
OO
N
F
F
F
F
White OLEDs (WOLEDs)
Gather, M. C.; Köhnen, A.; Meerholz, K. Adv. Mater. 2011, 23, 233.
white light = blended blue, green, red
Red PhOLED ✓
Green PhOLED ✓
Blue PhOLED ?
Solution: combine blue fluorescence with red/green phosphorescence
Working principle:
trap singlets on blue flourescent emittertrap triplets on red/green phosphorescent emitter
White OLEDs (WOLEDs)
Sun, Y.; Biebink, N. C.; Kanno, H.; Ma, B.; Thompson, M. E.; Forrest, S. R. Nature 2006, 440, 908.Chen, J.; Zhao, F.; Ma, D. Mater. Today 2014, 17, 175.
White OLEDs (WOLEDs)
Sun, Y.; Biebink, N. C.; Kanno, H.; Ma, B.; Thompson, M. E.; Forrest, S. R. Nature 2006, 440, 908.
NEt
2
BCzVBi
O
OMe
Me
IrIII
N
N
IrIII
N
N N
Ir(ppy)3 PQIr
Working principle:
trap singlets on blue flourescent emittertrap triplets on red/green phosphorescent emitter
White OLEDs (WOLEDs)
Schwartz, F.; Pfeiffer, M.; Reineke, S.; Walzer, K.; Leo, K. Adv. Mater. 2007, 19, 3672.Chen, J.; Zhao, F.; Ma, D. Mater. Today 2014, 17, 175.
White OLEDs (WOLEDs)
Schwartz, F.; Pfeiffer, M.; Reineke, S.; Walzer, K.; Leo, K. Adv. Mater. 2007, 19, 3672.Chen, J.; Zhao, F.; Ma, D. Mater. Today 2014, 17, 175.
O
OMe
Me
IrIII
N
N
N
N Me
Me
IrIII
N
N N
Ir(ppy)3 Ir(MDQ)2(acac)4P-NPD
N
2
Thermally-Activated Delayed Fluorescence (TADF)
Yang, Z. et al. Chem. Soc. Rev. 2017, 46, 915.
Obviously not phosphorescence
S0
S1T1
excit
on fo
rmat
ion
fluor
esce
nce
inte
rnal
con
vers
ion
ISC
phos
phor
esce
nce
alt-I
SC
excit
on fo
rmat
ion
RISC
eosin Y, 1961(E-type delayed fluorescence)
O O
Br
BrO
Br
Br
CO2“the high-frequency band (which has a contour
identical with the fluorescence band) is the result of thermal activation to the upper singlet
level folowed by a radiative transition from there to the ground state, and we shall therefore call
this the delayed fluorescence band”
Parker, C. A.; Hatchard, C. G. Trans. Faraday Soc. 1961, 57, 1894.
Thermally-Activated Delayed Fluorescence (TADF)
Yang, Z. et al. Chem. Soc. Rev. 2017, 46, 915.Adachi, C. et al. Appl. Phys. Lett. 2011, 98, 083302.
N N
NN N
NPh PhN
PIC-TRZ
E(T1) = 2.55 eVE(S1) = 2.66 eV
ΔEST = 0.11 eV
!ext = 5.3%
Thermally-Activated Delayed Fluorescence (TADF)
Yang, Z. et al. Chem. Soc. Rev. 2017, 46, 915.Uoyama, H.; Goushi, K.; Shizu, K.; Nomura, H.; Adachi, C. Nature 2012, 492, 234
NC CNN
NN N
4-CzIPN
Thermally-Activated Delayed Fluorescence (TADF)
Yang, Z. et al. Chem. Soc. Rev. 2017, 46, 915.Uoyama, H.; Goushi, K.; Shizu, K.; Nomura, H.; Adachi, C. Nature 2012, 492, 234
NC CNN
NN N
4-CzIPN
!ext = (19.3±1.5)%
Thermally-Activated Delayed Fluorescence (TADF)
Yang, Z. et al. Chem. Soc. Rev. 2017, 46, 915.Uoyama, H.; Goushi, K.; Shizu, K.; Nomura, H.; Adachi, C. Nature 2012, 492, 234
NC CNN
NN N
4-CzIPN
“Third-generation organic electroluminescence materials”
335 references in Review below, published Jan 2017