Articleshttps://doi.org/10.1038/s41566-018-0112-9

Diboron compound-based organic light-emitting diodes with high efficiency and reduced efficiency roll-offTien-Lin Wu   1, Min-Jie Huang1, Chih-Chun Lin1, Pei-Yun Huang1, Tsu-Yu Chou2, Ren-Wu Chen-Cheng2, Hao-Wu Lin   2*, Rai-Shung Liu1* and Chien-Hong Cheng   1*

1Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan. 2Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan. *e-mail: hwlin@mx.nthu.edu.tw; rsliu@mx.nthu.edu.tw; chcheng@mx.nthu.edu.tw

© 2018 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

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NaTuRe PHoToNiCS | www.nature.com/naturephotonics

S-1

Supplementary Information

Diboron compound-based organic light-emitting diodes with

high efficiency and reduced efficiency roll-off

Tien-Lin Wu1, Min-Jie Huang1, Chih-Chun Lin1, Pei-Yun Huang1, Tsu-Yu, Chou2,

Ren-Wu Chen-Cheng2, Hao-Wu Lin2*, Rai-Shung Liu1* and Chien-Hong Cheng1*

1Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan.

2Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu,

Taiwan.

*e-mail: hwlin@mx.nthu.edu.tw; rsliu@mx.nthu.edu.tw; chcheng@mx.nthu.edu.tw

S-2

Table of Contents:

Page

A. Synthetic procedure, characterization and NMR spectra…………………S-3

B. Single-crystal X-ray diffraction……………………………………………S-8

C. Photophysical, electrochemical and thermal properties………………….…S-10

D. OLED and lifetime device performance………………………………S-17

E. Computational data…………………………………………………………S-20

F. References.……………………………………………………………...S-26

S-3

A. Synthetic procedure, characterization and NMR spectrum

Scheme 1. Synthesis of 9-(4-bromo-3,5-dimethylphenyl)-9H-carbazole.

Synthesis of 9-(4-bromo-3,5-dimethylphenyl)-9H-carbazole. To a stirred solution of 2-bromo-

5-iodo-1,3-dimethylbenzene (2.00 g, 6.43 mmol), carbazole (1.18 g, 7.07 mmol), Cu (1.25 g,

19.68 mmol), K2CO3 (2.72 g, 19.68 mmol) and N,N-dimethylformamide (16 mL) was added under

a nitrogen atmosphere. The system was evacuated and purged with nitrogen three times and the

mixture was heated and stirred at 130 °C for 24 h. The reaction mixture was filtered through Celite

and washed with dichloromethane (20 mL). Solvent was evaporated under reduced pressure and

then purified by column chromatography (hexane / dichloromethane (10:1)) to afford the product

as a white solid in 91% yield. 1H NMR (400 MHz, CDCl3): δ 8.11 (d, J = 7.6 Hz, 2H), 7.41-7.35

(m, 4H), 7.28-7.24 (m, 4H), 2.50 (s, 6H). 13C NMR (100 MHz, CDCl3): δ140.7, 140.1, 136.1,

126.6, 126.1, 125.9, 123.3, 120.3, 119.9, 109.7, 24.0. HRMS Calcd for C20H16BrN: 349.0466.

Found: 349.0463.

Figure 1. 1H NMR spectrum of 9-(4-bromo-3,5-dimethylphenyl)-9H-carbazole.

S-4

Figure 2. 13C NMR spectrum of 9-(4-bromo-3,5-dimethylphenyl)-9H-carbazole.

Scheme 2. Synthesis of 9-(4-bromo-3,5-dimethylphenyl)-3,6-di-tert-butyl-9H-carbazole.

Synthesis of 9-(4-bromo-3,5-dimethylphenyl)-3,6-di-tert-butyl-9H-carbazole. A procedure

similar to the synthesis of 9-(4-bromo-3,5-dimethylphenyl)-9H-carbazole was used for the

synthesis of 9-(4-bromo-3,5-dimethylphenyl)-3,6-di-tert-butyl-9H-carbazole using 2-bromo-5-

iodo-1,3-dimethylbenzene (2.00 g, 6.43 mmol), carbazole (1.98 g, 7.07 mmol), Cu (1.25 g, 19.7

mmol), K2CO3 (2.72 g, 19.68 mmol) and N,N-dimethylformamide (16 mL) in 92% yield. White

solid. 1H NMR (400 MHz, CDCl3): δ 8.10 (d, J = 1.2 Hz, 2H), 7.44 (dd, J = 1.2, 8.8 Hz, 2H), 7.30

(d, J = 8.8 Hz, 2H), 7.25 (s, 2H), 2.48 (s, 6H), 1.44 (s, 18H). 13C NMR (100 MHz, CDCl3): δ

142.9, 139.9, 139.1, 136.6, 126.2, 125.6, 123.6, 123.3, 116.2, 109.1, 34.7, 32.0, 24.0. HRMS

Calcd for C28H32BrN: 461.1718. Found: 461.1725.

S-5

Figure 3. 1H NMR spectrum of 9-(4-bromo-3,5-dimethylphenyl)-3,6-di-tert-butyl-9H-carbazole.

Figure 4. 13C NMR spectrum of 9-(4-bromo-3,5-dimethylphenyl)-3,6-di-tert-butyl-9H-carbazole.

S-6

Figure 5. 1H NMR spectrum of CzDBA.

Figure 6. 13C NMR spectrum of CzDBA.

S-7

Figure 7. 1H NMR spectrum of tBuCzDBA.

Figure 8. 13C NMR spectrum of tBuCzDBA.

S-8

B. Single-crystal X-ray diffraction

Figure 9. a) The x-ray structure of CzDBA. b) The crystal packing of CzDBA viewing from b

axis. c) A side view of two CzDBA molecules, showing a shifted π–π stacking.

Figure 9 displays a dihedral angle between the DBA core and the phenylene bridge of 78°, and a

dihedral angle between the carbazole plane and the phenylene bridge of 70°. CzDBA was packed

in a C2/c space group.

S-9

Table 1. Crystal data and structure refinement for CzDBA.

Empirical formula C52 H40 B2 N2

Formula weight 714.48

Temperature 200(2) K

Wavelength 0.71073 Å

Crystal system Monoclinic

Space group C 2/c

Unit cell dimensions a = 26.1224(8) Å = 90°

b = 8.3077(3) Å = 106.476(2)°

c = 18.9832(6) Å = 90°

Volume 3950.5(2) Å 3

Z 4

Density (calculated) 1.201 Mg/m3

Absorption coefficient 0.068 mm-1

F(000) 1504

Crystal size 0.42 x 0.26 x 0.09 mm3

Theta range for data collection 2.72 to 25.05°

Index ranges -30<=h<=30, -8<=k<=9, -22<=l<=21

Reflections collected 12578

Independent reflections 3422 [R(int) = 0.0340]

Completeness to theta = 25.05° 97.8%

Absorption correction multi-scan

Max. and min. transmission 0.9939 and 0.9718

Refinement method Full-matrix least-squares on F2

Data / restraints / parameters 3422 / 0 / 253

Goodness-of-fit on F2 1.018

Final R indices [I>2sigma(I)] R1 = 0.0558, wR2 = 0.1639

R indices (all data) R1 = 0.0782, wR2 = 0.1786

Largest diff. peak and hole 0.356 and -0.247 e. Å -3

The crystallographic data for CzDBA and tBuCzDBA deposited on CCDC 1515214 and 1570473, respectively.

S-10

C. Photophysical, electrochemical and thermal properties

Photophysical characterization

Figure 10. Absorption spectra of a) CzDBA and b) tBuCzDBA measured at room temperature in

various solvents, and fluorescence spectra of c) CzDBA and d) tBuCzDBA at room temperature

measured in various solvents.

Lippert–Mataga analysis for the solvatochromic effect. Both DBA derivatives show an

absorption band at ~350 nm, a π to π* transition and a shoulder band around 430 nm assigned as

the ICT from the donor groups to DBA moiety. They exhibit clear solvatochromic shift of the

fluorescence spectra from green emissions 532 and 553 nm in toluene to orange-red emissions

601 and 628 nm in dichloromethane. The dependence of the Stokes shift between the absorbance

and PL spectra in each polar solvent can be constructed by the Lippert–Mataga equation: [1]

Stokes shift(𝛎𝐚 − 𝛎𝐩) = [2 (μ

𝑒− μ

𝑔)

ℎ𝑐a3] 𝑓(𝛆, 𝐧) + 𝑐𝑜𝑛𝑠𝑡.

300 400 5000.0

0.5

1.0

No

rma

lize

d I

nte

nsity (

a.u

.)

Wavelength (nm)

Toluene

Ethyl ether

Ethyl Acetate

Tetrahydrofuran

Dichloromethane

a

CzDBA

500 600 700 8000.0

0.5

1.0

Norm

aliz

ed

In

ten

sity (

a.u

.)

Wavelength (nm)

Toluene

Ethyl ether

Ethyl Acetate

Tetrahydrofuran

Dichloromethane

c

CzDBA

300 400 5000.0

0.5

1.0

Norm

aliz

ed

In

ten

sity (

a.u

.)

Wavelength (nm)

Toluene

Ethyl ether

Ethyl Acetate

Tetrahydrofuran

Dichloromethane

b

tBuCzDBA

500 600 700 8000.0

0.5

1.0N

orm

aliz

ed

In

ten

sity (

a.u

.)

Wavelength (nm)

Toluene

Ethyl ether

Ethyl Acetate

Tetrahydrofuran

Dichloromethane

d

tBuCzDBA

S-11

In the Lippert-Mataga formalism, ε and n denote the dielectric constant and the refractive index

of solvent, respectively. h is Planck’s constant, c is the speed of light. a is Onsager cavity radius.

μg and μe are dipole moments in the ground state and the excited state, respectively. The

orientation polarizability f(ε,n) is defined as follows:

𝒇(𝛆, 𝐧) = [𝛆 − 𝟏

𝟐𝛆 + 𝟏] − [

𝐧𝟐 − 𝟏

𝟐𝐧𝟐 − 𝟏]

Table 2. The UV-vis, PL data and Stokes shift for DBA compounds in different solvents.

Solvent

[1.0×10-5 M]

εa) na) f(ε,n)a) Absmax

[nm]b)

PLmax

[nm]b)

νa - νp

[cm-1]b)

Absmax

[nm]c)

PLmax

[nm]c)

νa - νp

[cm-1]c)

Toluene 2.4 1.497 0.0150 342 532 10442 348 553 10652

Diethyl ether 4.3 1.352 0.1659 342 551 11091 348 577 11405

Ethyl acetate 6.0 1.357 0.1995 342 575 11848 348 606 12234

Tetrahydrofuran 7.6 1.407 0.2098 342 594 12405 348 617 12528

Dichloromethane 8.9 1.424 0.2169 344 601 12431 350 628 12648

a) The ε and n values are obtained from http://www.stenutz.eu/chem/solv23.php. b) Absorption maximum (Absmax),

fluorescence maximum (PLmax) and Stokes shift (νa - νp) of CzDBA in different solvents. c) Absorption maximum

(Absmax), fluorescence maximum (PLmax) and Stokes shift (νa - νp) of tBuCzDBA in different solvents.

Figure 11. Lippert-Mataga plots for a) CzDBA and b) tBuCzDBA.

Based on the Lippert-Mataga equation calculated and performed above, the ∆μ (μe - μg) was

estimated via the linear slope from the Lippert-Mataga plots. For CzDBA and tBuCzDBA, the

slopes are 9240.7 cm-1 and 9358.9 cm-1, respectively. Thus, the singlet excited state exhibits a

larger dipole moment than that of the ground state for both compounds due to the intramolecular

charge transfer character of the excited state.

0.0 0.1 0.2

4.0k

8.0k

12.0k

16.0k CzDBA

Sto

ke

s s

hift

(cm

-1)

f

y = 9240.7x + 10152

a

0.0 0.1 0.2

4.0k

8.0k

12.0k

16.0k

tBuCzDBA

Sto

ke

s s

hift

(cm

-1)

f

y = 9358.9x + 10383

b

S-12

Figure 12. Phosphorescence spectra of 50-nm-thick doped film (10% DBA compound in CBP)

measured at different delayed times (0.5, 1.0 and 6.25 ms) for a) CzDBA and b) tBuCzDBA at

77 K. The spectra are essentially identical confirming that they are from the T1 state emission.

Table 3. Energy levels of S1 and T1.

Calculation Experiment

S1

[eV]a)

T1

[eV]a)

EST

[eV]a)

S1

[eV]b)

T1

[eV]c)

EST

[eV]d)

CzDBA 2.770 2.731 0.039 2.629 2.596 0.033

tBuCzDBA 2.651 2.625 0.026 2.486 2.464 0.022

a) The energy levels of S1 and T1 and the energy gaps were calculated by TD-DFT at BMK/6-31G* level. b) The singlet

energy level was calculated from the onset of the fluorescence spectrum of the co-doped film (10% DBA compound:

90% CBP). c) The triplet energy level was calculated from the onset of the phosphorescence spectrum of co-doped

film (10% DBA compound: 90% CBP). d) The energy gap between S1 and T1.

Figure 13. Comparison of the emission of a) CzDBA and b) tBuCzDBA in the doped films (10%

DBA compound: 90% CBP) and neat films. The emission bands in the neat films were slightly

red-shifted (16 and 8 nm, respectively) compared with those in the doped films.

400 500 600 7000.0

0.5

1.0

Inte

nsity (

a.u

.)

Wavelength (nm)

0.5 ms

1 ms

6.25 ms

tBuCzDBA

b

400 500 600 7000.0

0.5

1.0In

ten

sity (

a.u

.)

Wavelength (nm)

0.5 ms

1 ms

6.25 ms

CzDBA

a

500 5500.0

0.5

1.0

16 nm Red-shift

Inte

nsity (

a.u

.)

Wavelength (nm)

doped film

neat film

CzDBA

a

500 550 6000.0

0.5

1.0

8 nm Red-shift

Inte

nsity (

a.u

.)

Wavelength (nm)

doped film

neat film

b

tBuCzDBA

S-13

Table 4. Photoluminescence quantum yields (PLQYs) of CzDBA and tBuCzDBA in toluene and

thin films.

QYoxygen-bubbling

[%]a)

QY

[%]b)

QY degassing

[%]c)

QYdoped film

[%]d)

QYneat film

[%]e)

CzDBA 2.6 8.7 14.0 100 90.6

tBuCzDBA 2.5 7.4 11.9 86.0 84.0

a) Quantum yield in toluene solution with oxygen bubbling, estimated using 9,10-diphenylanthracence as the standard.

b) Quantum yield in toluene solution without degassing. c) Quantum yield in toluene solution with degassing.

d) Absolute total PL quantum yield in a 50-nm-thick co-doped film (10% DBA compound: 90% CBP) using an

integrating sphere. e) Absolute total PL quantum yield in each 50-nm-thick neat film using an integrating sphere.

Figure 14. Fluorescence and phosphorescence spectra at 77 K of a) CzDBA and b) tBuCzDBA

in toluene (1×10-5 M). The onset energy of fluorescence and phosphorescence spectra were used

to determine the S1 and T1 energy level. The ΔEST measured in toluene were 22 and 11 meV,

respectively for CzDBA and tBuCzDBA.

Transient PL measurement

Figure 15. Expanded decay curves of a) 10% CzDBA and b) 10% tBuCzDBA in CBP. Displayed

in the insets are their prompt decay curves in nanosecond scale.

500 6000.0

0.5

1.0

No

rma

lize

d I

nte

nsity (

a.u

.)

Wavelength (nm)

Flou, 77 K

Phos, 77 K

tBuCzDBA

b

500 6000.0

0.5

1.0

No

rma

lize

d I

nte

nsity (

a.u

.)

Wavelength (nm)

Fluo, 77 K

Phos, 77 K

CzDBA

a

0.0 0.5 1.0 1.5 2.010

-3

10-2

10-1

100

No

rma

lize

d I

nte

nsity (

a.u

.)

77 K

100 K

150 K

200 K

250 K

300 K

Time (μ s)

tBuCzDBA

b

0.0 0.5 1.0 1.5 2.010

-3

10-2

10-1

100

No

rma

lize

d I

nte

nsity (

a.u

.)

77 K

100 K

150 K

200 K

250 K

300 K

Time (μ s)

CzDBA

a

0 40 8010

-2

10-1

100

Inte

nsity (

a.u

.)

Time (ns)

300 K

0 40 8010

-2

10-1

100

Inte

nsity (

a.u

.)

Time (ns)

300 K

S-14

Figure 16. a) PL decay curves of CzDBA neat film (τp: 34 ns, τd: 1.0 μs) and tBuCzDBA neat

film (τp: 36 ns, τd: 1.2 μs) at 300 K. The delayed lifetimes of the emitters suffer only small

reduction compared to the reported literature.[2] b) PL decay curves of CzDBA in 1×10-5 M toluene

(τp: 92 ns, τd: 3.7 μs) and tBuCzDBA in 1×10-5 M toluene (τp: 109 ns, τd: 2.7 μs) at 300 K.

Fitting method. The fitting results are given by following equation:

𝑅(t) = 𝐵1𝑒(−𝑡/𝜏1) + 𝐵2𝑒(−𝑡/𝜏2) + 𝐵3𝑒(−𝑡/𝜏3)

Table 5. Fitting results of CzDBA and tBuCzDBA.

Condition τ1 = τp B1 τ2 B2 τ3 B3

[ns]c) [value] [μs]d) [value] [μs] [value]

CzDBAa) Doped film 22 20942 0.17 2160 3.81 508

tBuCzDBAa) 10% in CBP 34 23318 0.29 2766 3.22 414

CzDBAa) Neat film

34 41782 0.23 6237 3.11 161

tBuCzDBAa) 36 43203 0.25 6410 3.90 155

CzDBAb) Solution 92 9769 3.66 137 - -

tBuCzDBAb) 1×10-5 M toluene 109 9703 2.68 76 - -

a) The prompt and delayed component is best-fitted by three-exponentials for 10% CzDBA and 10% tBuCzDBA in

CBP or neat film (30 nm). b) The prompt and delayed component is best-fitted by two-exponentials for CzDBA and

tBuCzDBA in toluene (10-5 M).

To calculate the average delayed lifetime, we adopted the following equation:

τ𝑎𝑣

=[∑ 𝐵𝑖τ𝑖

2]

[∑ 𝐵𝑖τ𝑖], where B1 and τ1 are not included.

0 5 10

10-3

10-2

10-1

100

No

rma

lize

d I

nte

nsity (

a.u

.) CzDBA-neat film

tBuCzDBA-neat film

Time (μ s)

a

0 5 10 1510

-3

10-2

10-1

100

No

rma

lize

d I

nte

nsity (

a.u

.)

Time (μ s)

CzDBA-solution

tBuCzDBA-solution

b

S-15

The RISC rate constants (kRISC) of CzDBA and tBuCzDBA were determined by using a reported

method,[3] and kRISC is expressed as the following formula:

𝑘𝑝 = 𝛷𝑝/𝜏𝑝

𝛷𝑝 + 𝛷𝑑 = 𝑘𝑝/(𝑘𝑝 + 𝑘𝐼𝐶)

𝛷𝑝 = 𝑘𝑝/(𝑘𝑝 + 𝑘𝐼𝐶 + 𝑘𝐼𝑆𝐶)

𝛷𝐼𝑆𝐶 = 𝑘𝐼𝑆𝐶/(𝑘𝑝 + 𝑘𝐼𝐶 + 𝑘𝐼𝑆𝐶)

𝑘𝑑 = 𝛷𝑑/(𝛷𝐼𝑆𝐶𝜏𝑑)

𝑘𝑅𝐼𝑆𝐶 =𝑘𝑝𝑘𝑑

𝑘𝐼𝑆𝐶

𝛷𝑑

𝛷𝑝

Table 6. Detailed photophysical data and rate constants of CzDBA and tBuCzDBA.

Φp Φd kp kd kIC kISC kRISC ΔEST

[%]c) [%]c) [106 s-1]d) [105 s-1]e) [106 s-1]f) [107 s-1]g) [105 s-1]h) [meV]i)

CzDBAa) 16.5 83.5 7.50 3.13 0 3.80 3.13 54

tBuCzDBAa) 23.3 62.7 6.85 4.10 1.12 2.14 3.52 44

CzDBAb) 9.0 5.0 0.98 0.38 6.01 0.39 0.053 56

tBuCzDBA b) 10.0 1.9 0.92 0.44 6.79 0.15 0.052 50

a) 10% DBA compounds measured in CBP film (30 nm) at 300 K. b) DBA compounds measured in toluene (1×10-5

M) at 300 K. c) The prompt fluorescent (Φp) component and the delayed fluorescent (Φd) component of PLQY. d) The

rate constant of prompt component (kp). e) The rate constant of delayed component (kd). f) The rate constant of internal

conversion (kIC). g) The rate constant of intersystem crossing (kISC). h) The rate constant of reverse intersystem crossing

(kRISC). i) Calculated using equation: kd = (1/3)[kp × exp(−ΔEST/RT)], reported by Adachi et al.[4]

Photoelectron spectroscopy

Figure 17. Photoelectron spectra (AC-2) of a) CzDBA and b) tBuCzDBA neat films.

5.0 5.5 6.0

0

20

40 tBuCzDBA

(Yie

ld[c

ps])

1/2

Incident photon energy (eV)

b

5.88 eV

5.0 5.5 6.0

0

10

20

5.93 eV

CzDBA

(Yie

ld[c

ps])

1/2

Incident photon energy (eV)

a

S-16

Cyclic voltammetry

Figure 18. Cyclic voltammograms of CzDBA and tBuCzDBA. The oxidation was measured in

dichloromethane, while the reduction was in tetrahydrofuran.

For CV measurement from CzDBA and tBuCzDBA, the bipolar properties of these two

compounds were observed by the oxidation/reduction potentials of cyclic voltammetry in solution.

the HOMO levels are -5.57 and -5.48 eV, determined from their oxidation potentials,[5] and the

LUMO levels are -3.14 and -3.11 eV, respectively, obtained from the reduction potentials. In

addition, the gap between the oxidation and reduction potential of each compound gives the

energy difference, which is comparable to the optical Eg values, 2.48 and 2.39 eV, respectively.

The HOMO level of tBuCzDBA bearing two tert-butyl substituents on each carbazole group is

higher than that of CzDBA, the trend is also closed to the photoelectron results. However, their

LUMO levels determined by cyclic voltammetry, are quite close likely due to the successful

separation of HOMO/LUMO distribution.

Thermal properties

Figure 19. a) Thermal gravimetric analysis and b) differential scanning calorimetry (DSC)

analysis of CzDBA (black) and tBuCzDBA (red).

200 400 600 8000

50

100

Norm

aliz

ed m

ass r

em

ain

ing (

%)

Temperature (oC)

CzDBA

tBuCzDBA

a

100 150

Endoth

erm

ic

CzDBA

tBuCzDBA

b

Temperature (oC)

CzDBA

-1.5 -1.0 -0.5 0.00.0 0.5 1.0 1.5

tBuCzDBA

Potential (V)

Curr

en

t (A

)

S-17

D. OLED and lifetime device performance

Figure 20. The molecular structures of materials used in the devices.

In the devices A and B, N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) is

the hole transporter, tris(4-(9H-carbazol-9-yl)phenyl)amine (TCTA) acts as an electron/exciton

blocker to prevent exciton diffusion to the NPB layer, CBP is the host in which CzDBA and

tBuCzDBA were doped and 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB) is the electron

transporter. In the devices C, 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) is

hole injection material and 9,9′-diphenyl-6-(9-phenyl-9H-carbazol-3-yl)-9H,9′H-3,3′-bicarbazole

(Tris-PCz) is the hole transporter. 3,3'-di(9H-carbazol-9-yl)-1,1'-biphenyl (mCBP) is the host in

which CzDBA was doped. 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T) acts as an hole/exciton

blocker to prevent exciton diffusion to the 2,7-di(2,2'-bipyridin-5-yl)triphenylene (BPy-TP2)

electron transporting layer.

S-18

Table 7. External quantum efficiency and current efficiency of representative devices A and B at

1000 cd m-2, 3000 cd m-2 and 5000 cd m-2 with the corresponding efficiency roll-off values.

Device EQEmax

[%]a)

EQE1000

[%]b)

EQE3000

[%]c)

EQE5000

[%]d)

CEmax

[cd A-1]a)

CE1000

[cd A-1]b)

CE3000

[cd A-1]c)

CE5000

[cd A-1]d)

A 38.0 37.9

(0.3%)

36.2

(4.7%)

34.1

(10.3%) 141.0

140.6

(0.3%)

134.4

(4.7%)

127.1

(10.3%)

B 31.8 30.9

(2.3%)

27.6

(13.2%)

25.5

(19.9%) 129.4

125.7

(2.3%)

112.32

(13.2%)

103.7

(19.9%)

a) EQEmax and CEmax: the maximum external quantum efficiency and current efficiency, respectively. The EQE and

efficiency roll-off value in the parenthesis were measured at b) 1000 cd m-2, c) 3000 cd m-2 and d) 5000 cd m-2.

Figure 21. Hole-only and electron-only devices of a) CzDBA and b) tBuCzDBA.

Table 8. Summary of the performance of device C used for lifetime measurement using CzDBA

as the emitter.

Devicea) Vd ηEQE ηCE ηPE λEL CIE LT50 LT50

[V]b) [%]c) [cd A-1]d) [lm W-1]e) [nm]f) [x,y]g) [h]h) [h]i)

C 3.1 30.5 115.0 91.9 527 (0.30, 0.61) 97 ca. 315

a) Device configuration: ITO/HAT-CN (10 nm)/Tris-PCz (30 nm)/mCBP: CzDBA (10%) (30 nm)/T2T (10 nm)/BPy-

TP2 (40 nm)/LiF (1 nm)/Al (100 nm). b) The operating voltage at a brightness of 1 cd m-2. c) EQE, maximum external

quantum efficiency. d) CE, maximum current efficiency. e) PE, maximum power efficiency. f) The EL emission

wavelength at maximum intensity. g) CIE 1931 coordinates. h) A nominal lifetime to 50% initial luminance (LT50)

was measured at initial luminance of 1000 cd m-2. i) The predicted lifetime at initial luminance of 500 cd m-2 was

calculated by using the formula: LT50(L1) = LT50(L0) × (L0/L1)1.7.

0 2 4 6 8 10 1210

-3

10-2

10-1

100

101

102

103

Curr

ent

De

nsity (

mA

cm

-2)

Voltage (V)

Hole-only

Electron-only

CzDBA

a

0 2 4 6 8 10 1210

-3

10-2

10-1

100

101

102

103

Curr

ent D

ensity (

mA

cm

-2)

Voltage (V)

Hole-only

Electron-only

tBuCzDBA

b

S-19

Figure 22. a) Current density and luminance vs voltage characteristics. b) External quantum

efficiency vs luminance; inset: electroluminescent spectra. c) Current efficiency and power

efficiency vs luminance characteristics. d) Lifetime curves of device C and operating time was

measured at initial luminance of approximately 1000 cd m-2.

The operational lifetime (LT50) of the CzDBA-based device C is 97 h at 1000 cd m-2, estimated

for 315 h at 500 cd m-2. The configuration of device C is ITO/HAT-CN (10 nm)/Tris-PCz (30

nm)/CBP: CzDBA (10%) (30 nm)/T2T (10 nm)/BPy-TP2 (40 nm)/LiF (1 nm)/Al (100 nm),

similar to that reported by Adachi group.[6] We are expecting to greatly increase the device

operational lifetime after proper device optimization, encapsulation and improvement of the

fabrication environment.

100

101

102

103

104

105

0

50

100

150

Curr

en

t E

ffic

ien

cy (

cd A

-1)

Device C

Luminance (cd m-2)

0

50

100

150

Pow

er

Effic

ien

cy (

lm W

-1)

c

100

101

102

103

104

105

1

10

E.Q

.E.

(%)

Luminance (cd m-2)

Device C

b

300 400 500 600 700 8000.0

0.5

1.0 Device C

Inte

nsity (

a.u

.)

Wavelength (nm)

2 4 6 8 100

200

400

Device C

Lum

inance (

cd m

-2)

Curr

ent

De

nsity (

mA

cm

-2)

Voltage (V)

a

100

101

102

103

104

105

50 100

60

80

100

L/L

0 (

%)

Device C (1000 cd m-2)

Time (h)

d

0

S-20

E. Computational data

Table 9. Cartesian of optimized CzDBA.

Element X Y Z

C -0.69833256 3.79541491 -0.00205186

C 0.6988333 3.79532019 0.00104406

C 1.39585319 2.57713177 0.00215527

C 0.71626277 1.34464833 0.00127484

C -0.71608143 1.34474565 -0.00202697

C -1.39551218 2.57731861 -0.00302638

B 1.50404394 -0.00013328 -0.00031276

C 0.71608041 -1.34480042 -0.00197265

C -0.71626383 -1.34470301 0.00134017

B -1.50404498 0.00007857 -0.00029546

C 1.39551147 -2.57737336 -0.00292233

C 0.69833184 -3.7954695 -0.0018882

C -0.69883409 -3.79537475 0.00121809

C -1.39585423 -2.57718655 0.00227971

C -3.07606522 0.00016177 -0.00022592

C 3.07606417 -0.00021426 -0.00022041

C -3.79691908 0.07429346 -1.21685978

C -5.19803992 0.08242279 -1.20880841

C -5.90175902 0.00020246 -0.00008323

C -5.19791869 -0.08201485 1.20857189

C -3.79679965 -0.07392818 1.21648106

C 3.79693412 -0.07440026 -1.21684099

C 5.19805484 -0.082514 -1.20877127

C 5.90175844 -0.00022211 -0.00004143

C 5.19790151 0.08203753 1.20860121

C 3.7967824 0.07393551 1.21649256

N -7.31855617 0.000184 -0.00000746

N 7.3185558 -0.00017104 0.00005227

C 3.04672282 -0.15556264 -2.53762417

C 3.0464006 0.15507904 2.53717989

C -3.04643764 -0.15501956 2.53718265

C -3.04669066 0.15538091 -2.53763803

C -8.13152092 0.85087718 0.74594962

C -9.49327511 0.54657341 0.47934165

C -9.49331692 -0.54661324 -0.47870246

C -8.13158574 -0.85067725 -0.74570648

S-21

C 8.13153076 -0.85081301 0.74605701

C 9.49328131 -0.5464889 0.47945411

C 9.49331099 0.54666018 -0.47863299

C 8.13157643 0.85068423 -0.7456648

C 7.77135907 -1.89369338 1.61328446

C 8.79984966 -2.61212763 2.2260778

C 10.15673268 -2.3105728 1.98446028

C 10.50799747 -1.2827605 1.1093797

C 10.50806801 1.28316563 -1.10821689

C 10.15686116 2.31091997 -1.98338975

C 8.79999063 2.61218071 -2.22543234

C 7.77145998 1.89350949 -1.61298271

C -10.50808129 -1.28311957 -1.10827358

C -10.15688423 -2.31091126 -1.98340623

C -8.80001672 -2.61220737 -2.22542434

C -7.77147866 -1.89353598 -1.61298705

C -7.7713361 1.89378546 1.61313826

C -8.79981765 2.61226937 2.22588868

C -10.15670442 2.31073582 1.98426602

C -10.50798201 1.28289501 1.10922358

H -1.24559573 4.73704119 -0.00341325

H 1.24622363 4.73687261 0.00230738

H 2.4856184 2.58388489 0.00397814

H -2.48527752 2.58420429 -0.00483281

H 2.48527677 -2.58425901 -0.00473938

H 1.24559493 -4.73709588 -0.00321306

H -1.2462242 -4.73692724 0.00252724

H -2.48561939 -2.58393982 0.00411192

H -5.75255427 0.16426647 -2.14226675

H -5.75234276 -0.16383705 2.14208607

H 5.75258073 -0.1643975 -2.14221899

H 5.75231312 0.16391258 2.14211816

H 2.42443255 0.73795848 -2.69193008

H 3.73515049 -0.23985553 -3.38670441

H 2.37521697 -1.02595148 -2.5546963

H 3.73470476 0.23971757 3.38632524

H 2.37463017 1.02526693 2.55402877

H 2.42436215 -0.73860627 2.69155469

H -3.73475729 -0.23956771 3.38632458

S-22

H -2.37470915 -1.02523869 2.55409994

H -2.42435874 0.73864629 2.69150556

H -2.4244312 -0.73816851 -2.69190532

H -3.73510614 0.23966786 -3.38672868

H -2.37515316 1.02574459 -2.55473406

H 6.72855296 -2.14008468 1.79535533

H 8.54512384 -3.42575477 2.9028736

H 10.93270846 -2.88938483 2.48089317

H 11.5544187 -1.05416693 0.91263043

H 11.55447495 1.05481301 -0.91111254

H 10.93286959 2.88991401 -2.47955892

H 8.54529995 3.42576877 -2.90228874

H 6.72866631 2.13969432 -1.79539068

H -11.55448622 -1.05473744 -0.91119252

H -10.93289896 -2.88990562 -2.47956541

H -8.5453352 -3.42582161 -2.90225253

H -6.728686 -2.13974262 -1.7953751

H -6.7285265 2.1401594 1.79521179

H -8.5450814 3.42591816 2.90265444

H -10.93267332 2.88958648 2.48066462

H -11.55440605 1.05431775 0.91247028

Table 10. Cartesian of optimized tBuCzDBA.

Element X Y Z

C -0.6985901 -3.79507182 0.00080279

C 0.6985598 -3.7950783 -0.00082442

C 1.39572278 -2.57693435 -0.00126685

C 0.71617122 -1.34444973 -0.00041431

C -0.71617941 -1.34444297 0.00042603

C -1.39574197 -2.57692146 0.0012629

B 1.50443328 0.00016933 0.00016785

C 0.71618231 1.34479583 0.00065646

C -0.71616876 1.34480257 -0.00043134

B -1.50443082 0.00018244 -0.00013569

C 1.39574462 2.57727437 0.00168012

C 0.69859266 3.79542461 0.00118447

C -0.69855696 3.79543117 -0.00067087

C -1.39572002 2.5772874 -0.00131193

S-23

C -3.07641331 0.00018362 -0.00009026

C 3.07641561 0.00016183 0.00014349

C -3.79795346 -0.00604502 1.21839417

C -5.19899266 -0.01551649 1.21100763

C -5.90408798 0.00012889 -0.00002222

C -5.19905063 0.01579443 -1.21108484

C -3.79801184 0.00638017 -1.21854062

C 3.79801074 0.00633926 1.21859534

C 5.19905014 0.01575337 1.21114336

C 5.90408862 0.00010895 0.00008053

C 5.1989963 -0.01549451 -1.21095087

C 3.79795765 -0.00602927 -1.21834024

N -7.31906238 0.00006211 -0.0000015

N 7.31906313 0.00005453 0.00004373

C 3.04989009 0.0187651 2.54306098

C 3.04977534 -0.01840692 -2.54277141

C -3.04989755 0.01883551 -2.5430096

C -3.0497723 -0.01850934 2.54282564

C -8.13460194 -0.86669203 -0.72649123

C -9.49562011 -0.55825186 -0.46704592

C -9.49568303 0.55809221 0.46708795

C -8.13469862 0.86672269 0.72649706

C 8.13466232 0.86675139 -0.72644857

C 9.49565927 0.55813995 -0.46709033

C 9.49564403 -0.55823936 0.46700113

C 8.13463851 -0.86671907 0.72647334

C 7.79337284 1.92998522 -1.56949814

C 8.8300751 2.6601083 -2.1602422

C 10.19627058 2.36887878 -1.93603876

C 10.51025689 1.305963 -1.07455276

C 10.51022096 -1.30617332 1.07436225

C 10.19620448 -2.36906823 1.935862

C 8.83000012 -2.66016334 2.1601846

C 7.79331855 -1.92993181 1.56953864

C -10.5103159 1.30587755 1.07453844

C -10.1963797 2.36877502 1.93606395

C -8.83019803 2.66002963 2.16031534

C -7.79346143 1.92994752 1.56958156

C -7.79323219 -1.92985201 -1.56960043

S-24

C -8.82988031 -2.66007609 -2.16031393

C -10.19609817 -2.36902097 -1.9360193

C -10.51016355 -1.30617463 -1.0744765

C 11.33610065 3.17881429 -2.58968639

C 10.80800408 4.29173459 -3.52179039

C 12.2299994 2.23060133 -3.4307326

C 12.19749669 3.84332941 -1.48423363

C 11.33601249 -3.17913467 2.58938251

C 10.80789433 -4.29176126 3.52182493

C 12.23032701 -2.23095721 3.43002591

C 12.19698763 -3.84404912 1.48384218

C -11.33624765 3.17867047 2.58969233

C -10.8082094 4.29139578 3.52206225

C -12.23032288 2.23036511 3.43044616

C -12.19744642 3.84343172 1.48423408

C -11.33586765 -3.17907499 -2.58962314

C -10.80769372 -4.29172041 -3.52201141

C -12.23009883 -2.23089338 -3.43035071

C -12.1969436 -3.84396411 -1.48414604

H -1.24592191 -4.73668088 0.00166695

H 1.24588299 -4.73669233 -0.00170066

H 2.48547643 -2.5836004 -0.00261178

H -2.48549578 -2.58357829 0.00260653

H 2.48549811 2.58393196 0.00321653

H 1.24592425 4.73703361 0.0022023

H -1.24587991 4.73704529 -0.00157933

H -2.48547338 2.58395439 -0.00285242

H -5.75223734 -0.04858767 2.14807889

H -5.75234545 0.04880766 -2.1481294

H 5.75234127 0.0487551 2.14818989

H 5.75224645 -0.04852816 -2.14802097

H 2.41051705 -0.87031002 2.64286602

H 3.74117744 0.03618095 3.39391494

H 2.39628112 0.89971675 2.61854297

H 3.74101724 -0.03619551 -3.39365439

H 2.39585769 -0.89914384 -2.61808056

H 2.41070348 0.87087304 -2.6426878

H -3.74119031 0.03623735 -3.39385941

H -2.3963142 0.89980638 -2.61849026

S-25

H -2.41049962 -0.87022046 -2.6428235

H -2.41032227 0.87051519 2.64258652

H -3.74102257 -0.0358535 3.39371114

H -2.39623289 -0.89951392 2.61829709

H 6.75472766 2.19075832 -1.75662337

H 8.55700033 3.48382143 -2.81349113

H 11.55043468 1.05576596 -0.86893172

H 11.55040621 -1.05608106 0.86865071

H 8.55690153 -3.48386946 2.81343271

H 6.75466537 -2.19061381 1.75674389

H -11.55048241 1.05566593 0.86887706

H -8.55716188 3.48374136 2.81358244

H -6.75483212 2.19075473 1.7567394

H -6.75456562 -2.19049576 -1.75678908

H -8.55674399 -3.48373927 -2.81360049

H -11.55035996 -1.05610949 -0.86878827

H 10.19700571 5.02205208 -2.97479592

H 11.65587881 4.83021775 -3.96556983

H 10.20522103 3.87896231 -4.34182118

H 12.67290615 1.44121118 -2.81058632

H 13.04937327 2.79556631 -3.89739747

H 11.64427226 1.74870367 -4.22480125

H 13.02069101 4.41548909 -1.9353492

H 11.59028501 4.52972105 -0.87904038

H 12.6340167 3.09440107 -0.81107158

H 10.19637356 -5.02189305 2.97516453

H 11.65575466 -4.83052626 3.96528992

H 10.20563019 -3.87867801 4.34207963

H 12.67321053 -1.44175643 2.80962082

H 13.04972136 -2.79600202 3.8965583

H 11.64491277 -1.74881265 4.22417543

H 13.02015231 -4.4163258 1.93486343

H 11.58946987 -4.53040242 0.87891265

H 12.63352679 -3.09534279 0.81044625

H -10.19693094 5.02166273 2.97531204

H -11.65610974 4.829979 3.96567128

H -10.20572433 3.87842871 4.34221351

H -12.67315851 1.44109027 2.81010152

H -13.04974988 2.79529052 3.89706589

S-26

H -11.64474545 1.7483179 4.22453453

H -13.02065842 4.41557798 1.93533448

H -11.59010329 4.5298786 0.87923557

H -12.63393304 3.09464788 0.81089

H -10.1962973 -5.02190225 -2.97527947

H -11.65552817 -4.83042249 -3.96560219

H -10.20528781 -3.87866276 -4.34217519

H -12.67303638 -1.4416874 -2.80999131

H -13.04945365 -2.79593477 -3.89695686

H -11.64460871 -1.74875564 -4.22444847

H -13.020084 -4.41622802 -1.93522803

H -11.58948712 -4.5303252 -0.87916391

H -12.63352181 -3.09524483 -0.8107895

F. References

[1] Lai, C.-C. et al. m-Indolocarbazole derivative as a universal host material for RGB and white

phosphorescent OLEDs. Adv. Funct. Mater. 25, 5548-5556 (2015).

[2] Guo, J. et al. Achieving high-performance nondoped OLEDs with extremely small efficiency

roll-off by combining aggregation-induced emission and thermally activated delayed

fluorescence. Adv. Funct. Mater. 27, 1606458 (2017).

[3] Goushi, K., Yoshida, K., Sato, K. & Adachi, C. Organic light-emitting diodes employing

efficient reverse intersystem crossing for triplet-to-singlet state conversion. Nat. Photon. 6,

253–258 (2012).

[4] Zhang, Q. S. et al. Anthraquinone-based intramolecular charge-transfer compounds:

computational molecular design, thermally activated delayed fluorescence, and highly

efficient red electroluminescence. J. Am. Chem. Soc. 136, 18070-18081 (2014).

[5] Wu, T.-L., Chou, H.-H., Huang, P.-Y., Cheng, C.-H. & Liu, R.-S. 3,6,9,12-tetrasubstituted

chrysenes: synthesis, photophysical properties, and application as blue fluorescent OLED. J.

Org. Chem. 79, 267-274 (2014).

[6] Tsang, D. P., Matsushima, T. & Adachi, C. Operational stability enhancement in organic

light-emitting diodes with ultrathin Liq interlayers. Sci. Rep. 6, 22463 (2016).