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Supporting Information:
Efficient blue organic light-emitting diodes employing thermally
activated delayed fluorescence
Qisheng Zhang,§ Bo Li,§ Shuping Huang, Hiroko Nomura, Hiroyuki Tanaka &
Chihaya Adachi*
[*] Prof. C. Adachi1,2, Dr. Q. Zhang1, B. Li1, Dr. S. Huang1, H. Nomura1, Dr. H.
Tanaka1
Center for Organic Photonics and Electronics Research (OPERA)1 and International
Institute for Carbon Neutral Energy Research2, Kyushu University
744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
E-mail: [email protected]
[§] These authors contributed equally.
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Contents
1. Materials and synthesis
2. Computational data
3. Photoluminescence data
4. The lowest triplet energy level of DPEPO
5. The comparison between DMAC-DPS and FIrpic
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1. Materials and synthesis
General: Reagents and anhydrous solvents were purchased from commercial sources
and used as received. DPEPO was prepared by a procedure in the literature1 and was
further purified by sublimation twice. Other OLED materials were purchased from
Luminescence Technology Corporation (Taiwan) and were used without further
purification. The six TADF compounds investigated in this paper were synthesized by
the procedures described below. The starting materials 1,4-dichloro-1,4-bisphenyl-
2,3-diaza-1,3-butadiene,2 5-phenyl-5,10-dihydrophenazine,3 2-(4-bromo-phenyl)-
5-phenyl-1,3,4-oxadiazole,4 3-(4-bromophenyl)-4.5-diphenyl-1,2,4-triazole5 and
9,9-dimethyl-9,10-dihydroacridine6 were prepared following literature procedures. 1H
nuclear magnetic resonance (NMR) and 13C NMR spectra were recorded in DMSO-d6
with a Bruker Avance 500 spectrometer (Germany) operating at 500 MHz for 1H
NMR and 125 MHz for 13C NMR. Chemical shifts (δ) are given in parts per million
(ppm) relative to tetramethylsilane (TMS; δ = 0) as the internal reference. 1H NMR
spectra data are reported as chemical shift, relative integral, multiplicity (s = singlet, d
= doublet, t = triplet, m = multiplet), coupling constant (J in Hz) and assignment.
Mass spectra were measured in positive ion atmospheric pressure chemical ionization
(APCI) mode on a Waters 3100 mass detector. Elemental analyses (C, H, N) were
carried out with a Yanaco MT-5 CHN corder.
4-(4-Bromophenyl)-3,5-diphenyl-1,2,4-triazole:
1,4-Dichloro-1,4-bisphenyl-2,3-diaza-1,3-butadiene (4.5 g, 16 mmol), 4-bromoaniline
(2.0 g, 16 mmol) and N,N-dimethylaniline (30 mL) were added into a 100-mL
three-necked flask. After the mixture was stirred for 5 h at 135 C under nitrogen
atmosphere, it was poured into 1M hydrochloric acid solution (100 mL) and stirred
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for another 0.5 h. The precipitate was collected by filtration and then dissolved in
toluene. The organic layer was washed with saturated sodium carbonate solution and
then dried over anhydrous magnesium sulfate. After evaporation of the solvent, the
crude product was recrystallized from ethanol and hexane to obtain a white powder
(2.3 g, 38%). 1H NMR (DMSO-d6, 500 MHz): δ [ppm] 7.67 (d, J = 8.5 Hz, 2H),
7.43–7.38 (m, 12H). 13C NMR (DMSO-d6, 125 MHz): δ [ppm] 154.2, 134.2, 132.7,
130.5, 129.7, 128.6, 128.5, 126.8, 122.9. APCI-MS m/z: 376 [M+1]+. Anal. calcd for
C20H14BrN3: C, 63.84; H, 3.75; N, 11.17. Found: C, 63.97; H, 3.71; N, 11.19.
2-[4-(5-Phenyl-5,10-dihydrophenazine)phenyl]-5-phenyl-1,3,4-oxadiazole
(PPZ-DPO): A toluene solution of freshly prepared 5-phenyl-5,10-dihydrophenazine
(10 mL, ca. 6 mmol) and tri(tert-butyl)phosphine toluene (0.63 mL, 2 mol/L) was
added to a 100-mL three-necked flask containing 2-(4-bromophenyl)-5-phenyl-
1,3,4-oxadiazole (1.50 g, 5 mmol), palladium acetate (0.056 g, 0.25 mmol), potassium
carbonate (1.84 g, 13.3 mmol), and toluene (10 mL) under nitrogen protection. The
mixture was stirred for 10 h at 80 C under nitrogen atmosphere. Water (10 mL) and
chloroform (100 mL) were then added under stirring. The organic layer was separated
and dried with anhydrous magnesium sulfate. After filtration and evaporation of
solvent, the residue was purified by column chromatography on silica gel (toluene:
ethyl acetate = 4:1), giving the desired compound as a yellow powder (1.95 g, 82%). 1H NMR (DMSO-d6, 500 MHz): δ [ppm] 8.42 (d, J = 8.5 Hz, 2H), 8.18 (d, J = 8.0 Hz,
2H), 7.72–7.66 (m, 7H), 7.55 (t, J = 7.5 Hz, 1H), 7.43 (d, J = 8.5 Hz, 2H), 6.36–6.32
(m, 4H), 5.69 (d, J = 9.0 Hz, 2H), 5.58 (d, J = 9.0 Hz, 2H). 13C NMR (DMSO-d6, 125
MHz): δ [ppm] 164.2, 163.6, 143.4, 139.4, 136.3, 135.2, 132.1, 131.6, 131.5, 130.8,
130.0, 129.5, 128.5, 126.7, 123.3, 122.9, 121.5, 121.0, 113.0, 112.5. APCI-MS m/z:
478 [M+1]+. Anal. calcd for C32H22N4O: C, 80.32; H, 4.63; N, 11.71. Found: C, 80.45;
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H, 4.59; N, 11.63.
3-[4-(5-Phenyl-5,10-dihydrophenazine)phenyl]-4,5-diphenyl-1,2,4-triazole
(PPZ-3TPT): A procedure similar to that used for PPZ-DPO was followed, but with
3-(4-bromophenyl)-4.5-diphenyl-1,2,4-triazole (1.88 g, 5 mmol) instead of 3-(4-
bromophenyl)-5-phenyl-1,2,4-oxadiazole. After evaporation of the solvent, the crude
product was subjected to column chromatography on silica gel (toluene: ethyl acetate
= 2:1), giving the desired compound as a yellow powder with a yield of 64%. 1H
NMR (DMSO-d6, 500 MHz): δ [ppm] 7.70–7.67 (m, 4H), 7.55–7.48 (m, 6H), 7.43–
7.38 (m, 9H), 6.30–6.27 (m, 4H), 5.52–5.47 (m, 4H). 13C NMR (DMSO-d6, 125
MHz): δ [ppm] 154.4, 153.7, 141.0, 139.4, 136.1, 135.4, 134.8, 131.5, 130.8, 129.9,
129.7, 128.5, 128.3, 126.9, 121.2, 120.9, 112.4, 112.3. APCI-MS m/z: 554 [M+1]+.
Anal. calcd for C38H27N5: C, 82.44; H, 4.92; N, 12.65. Found: C, 82.35; H, 4.92; N,
12.57.
4-[4-(5-Phenyl-5,10-dihydrophenazine)phenyl]-3,5-diphenyl-1,2,4-triazole
(PPZ-4TPT): A procedure similar to that used for PPZ-DPO was followed but with
4-(4-bromophenyl)-3,5-diphenyl-1,2,4-triazole (1.88 g, 5 mmol) instead of 3-(4-
bromophenyl)-5-phenyl-1,2,4-oxadiazole. After evaporation of the solvent, the crude
product was subjected to column chromatography on silica gel (toluene: ethyl acetate
= 2:1), giving the desired compound as a yellow powder with a yield of 54%. 1H
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NMR (DMSO-d6, 500 MHz): δ [ppm] 7.72–7.68 (m, 4H), 7.55–7.52 (m, 3H), 7.50–
7.40 (m, 12H), 6.37–6.30 (m, 4H), 5.53 (d, J = 7.5 Hz, 2H), 5.47 (d, J = 7.5 Hz, 2H). 13C NMR (DMSO-d6, 125 MHz): δ [ppm] 154.2, 140.7, 139.4, 136.0, 135.4, 134.6,
132.5, 131.9, 131.6, 130.7, 129.8, 128.6, 128.5, 128.4, 126.9, 121.3, 120.9, 112.3,
112.1. APCI-MS m/z: 555 [M+1]+. Anal. calcd for C38H27N5: C, 82.44; H, 4.92; N,
12.65. Found: C, 82.53; H, 4.83; N, 12.58.
Bis[4-(5-phenyl-5,10-dihydrophenazine)phenyl]sulfone (PPZ-DPS): Sodium
hydride (0.72 g, 30 mmol) was added to a solution of 5-phenyl-5,10-
dihydrophenazine (3.87 g, 15 mmol) in dry dimethylformamide (DMF) (30 mL).
After the solution was stirred at room temperature for 30 min, bis(p-fluorophenyl)
sulfone (1.91 g, 7.5 mmol) in dry DMF (30 mL) was added, and then the mixture was
stirred at 50 °C for 1 h. After cooling, the mixture was poured into water (400 mL),
and the resulting orange precipitate was filtered and washed by methanol. The crude
product was recrystallized from chloroform and methanol to produce orange crystals
(2.7 g, 50%). 1H NMR (DMSO-d6, 500 MHz): δ [ppm] 8.21 (d, J = 8.5 Hz, 4H),
7.70–7.64 (m, 8H), 7.54 (t, J = 7.5 Hz, 2H), 7.40 (d, J = 8.0 Hz, 4H), 6.50–6.44 (m,
8H), 5.93 (d, J = 7.5 Hz, 4H), 5.71 (d, J = 7.5 Hz, 4H). 13C NMR (DMSO-d6, 125
MHz): δ [ppm] 146.4, 139.1, 138.7, 137.5, 133.9, 131.4, 130.7, 130.6, 128.9, 128.6,
122.5, 121.1, 115.4, 112.9. APCI-MS m/z: 730 [M+1]+. Anal. calcd for C48H34N4O2S:
C, 78.88; H, 4.69; N, 7.67. Found: C, 79.08; H, 4.61; N, 7.56.
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Bis[4-(phenoxazine)phenyl]sulfone (PXZ-DPS): A procedure similar to that used
for PPZ-DPS was followed but with phenoxazine (2.75 g, 15 mmol) instead of
5-phenyl-5,10-dihydrophenazine. After reaction, the mixture was poured into water
(400 mL), and the bright yellow precipitate (3.9 g) was collected in 90% yield. 1H
NMR (DMSO, 500 MHz): δ [ppm] 8.30 (d, J = 9.0 Hz, 4H), 7.75 (d, J = 8.5 Hz, 4H),
6.80 (d, J = 7.5 Hz, 4H), 6.74 (t, J = 7.5 Hz, 4H), 6.69 (t, J = 7.5 Hz, 4H), 5.97 (d, J =
8.0 Hz, 4H). 13C NMR (DMSO-d6, 125 MHz): δ [ppm] 143.8, 143.5, 140.2, 132.9,
131.6, 130.8, 123.8, 122.3, 115.6, 113.9. APCI-MS m/z: 580 [M+1]+. Anal. calcd for
C36H24N2O4S: C, 74.47; H, 4.17; N, 4.82. Found: C, 74.49; H, 4.08; N, 4.80.
Bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS): A
procedure similar to that used for PPZ-DPS was followed but with
9,9-dimethyl-9,10-dihydroacridine (3.14 g, 15 mmol) instead of 5-phenyl-5,10-
dihydrophenazine. The crude product was recrystallized from chloroform and
methanol to produce pale yellow crystals (3.7 g, 78%). 1H NMR (DMSO-d6, 500
MHz): δ [ppm] 8.31 (d, J = 9.0 Hz, 4H), 7.69 (d, J = 8.5 Hz, 4H), 7.52 (d, J = 7.5 Hz,
4H), 7.05–6.96 (m, 8H), 6.29 (d, J = 8.0 Hz, 4H), 3.32 (s, 12H). 13C NMR (DMSO-d6,
125 MHz): δ [ppm] 146.1, 139.7, 139.4, 131.5, 130.5, 126.6, 125.5, 121.6, 115.0, 35.8,
30.7. APCI-MS m/z: 633 [M+1]+. Anal. calcd for C42H36N2O2S: C, 79.72; H, 5.73; N,
4.43. Found: C, 79.16; H, 5.71; N, 4.37.
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2. Computational data
Table S1. Calculated EVA(S1) and EVA(T1) using various exchange-correlation functionals and 6-31G* basis set based on B3LYP optimized geometries, and calculated CT amount (q), optimal HF% (OHF), E0-0(3LE), E0-0(1CT) and E0-0(3CT) of the compounds in toluene. parameter functional PPZ-DPO PPZ-3TPT PPZ-4TPT PPZ-DPS PXZ-DPS DMAC-DPS
EVA(S1)
(eV)
B3LYP 7,8 1.9128 2.3443 2.5436 2.0632 2.4452 2.7622
PBE0 9,10 2.0970 2.5193 2.7079 2.2317 2.6154 2.9254
MPW1B95 11 2.2889 2.6972 2.8648 2.4066 2.7834 3.0825
BMK 12 2.6394 3.0378 3.1808 2.7450 3.1189 3.4200
M06-2X 13 2.9470 3.2975 3.3787 3.0005 3.3545 3.6333
M06-HF 14 3.7747 3.7611 3.8094 3.7629 4.0808 4.2849
EVA(T1)
(eV)
B3LYP 1.9025 2.3321 2.4805 2.0530 2.4147 2.7516
PBE0 2.0829 2.4460 2.4723 2.2180 2.5744 2.9103
MPW1B95 2.2764 2.6183 2.6449 2.3947 2.7465 3.0700
BMK 2.6227 2.7288 2.7609 2.7282 3.0699 3.4021
M06-2X 2.8944 2.8867 2.9230 2.8947 3.2706 3.6240
M06-HF 3.1863 3.1694 3.2176 3.1855 3.6352 4.0395
E0-0(3LE) a
(eV)
BMK 2.39 2.42
M06-2X 2.36 2.36 2.39 2.36
M06-HF 2.36 2.35 2.39 2.36 2.71 3.02
Average 2.36 2.37 2.40 2.36 2.71 3.02
CT amount (e)b 0.920 0.920 0.900 0.880 0.861 0.850
optimal HF% c 39 39 38 37 36 36
EVA(S1, OHF) d (eV) 2.56 2.93 3.06 2.60 2.95 3.24
E0-0(1CT) e (eV) 2.32 2.69 2.82 2.36 2.71 3.00
E0-0(3CT) f (eV) 2.30 2.67 2.73 2.34 2.66 2.98
a) E0-0(3LE) = EVA(T1)/C-0.09 eV, where C is 1.10, 1.18, and 1.30 for BMK, M06-2X and M06-HF results,
respectively. b) Orbital compositions were analyzed using Multiwfn.15 c) OHF = 42q.16 d) The EVA(S1)
corresponding to the OHF can be read from the best fit straight line for a double log plot of EVA(S1) against HF%
(see Fig. S2). e) E0-0(1CT) = EVA(S1, OHF)-0.24 eV.14 f) E0-0(3CT) = E0-0(S1)-EVA(S1, OHF)+EVA(S1, OHF)/EVA(S1,
B3LYP)×EVA(T1, B3LYP).14
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Compound HOMO LUMO
PPZ-DPO
PPZ-3TPT
PPZ-DPS
PXZ-DPS
Figure S1. HOMO and LUMO of the S0 states of the compounds calculated at the B3LYP/6-31G*
level.
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Figure S2. Dependence of EVA(S1) and EVA(T1) on the HF% in TD-DFT for (a) PPZ-DPO, (b) PPZ-3TPT, (c) PPZ-4TPT, (d) PPZ-DPS, (e) PXZ-DPS and (f) DMAC-DPS, plotted on a log-log scale.
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3. Photoluminescence data
Table S2. Photophysical, excited-state energy and molecular orbital data measured for the compounds at room temperature. parameter PPZ-DPO PPZ-3TPT PPZ-4TPT PPZ-DPS PXZ-DPS DMAC-DPS
in toluene (0.1 mM)
λmax,em (nm) 577 528 495 577 507 460
F 0.08 0.04 0.03 0.02 0.22 0.16
TADF 0.04 0.03 – 0.01 0.59 0.64
F (ns) 9.0 3.9 3.6 5.6 15 20
TADF (μs) 0.52 33 – 0.28 2.5 7.1
kF (×107 s-1) 0.9 1.0 0.8 0.4 1.5 0.8
kTADF (×105 s-1) 0.8 0.009 – 0.4 2.4 0.9
E0-0(1CT) a,b 2.40 (2.32) 2.65 (2.69) 2.80 (2.82) 2.40 (2.36) 2.73 (2.71) 3.00 (3.00)
E0-0(3CT) a,c 2.31 (2.30) (2.67) (2.74) 2.31 (2.34) 2.65 (2.66) 2.91 (2.98)
E0-0(3LE) a,d 2.38 (2.36) 2.38 (2.37) 2.38 (2.40) 2.37 (2.36) (2.71) (3.02)
in mCP film (10 wt%)
λmax,em (nm) 550 520 474 580 505 464
F 0.12 0.06 0.04 0.08 0.24 0.23
TADF 0.33 0.36 0.08 0.12 0.66 0.57
F (ns) 7 3.5 2.8 10 14 21
TADF (μs) 2.4 4.9×103 2.8×104 1.0 2.6 3.1
kF (×107 s-1) 1.7 1.7 1.4 0.8 1.7 1.1
kTADF (×105 s-1) 1.4 7.3×10-4 2.9×10-5 1.2 2.5 1.8
E0-0(1CT) b 2.46 2.68 2.81 2.43 2.74 2.99
E0-0(3CT) b 2.38 2.35 2.66 2.91
E0-0(3LE) e 2.38 2.38 2.38
neat film
HOMO (eV) 4.91 4.85 4.85 5.10 5.59 5.92
LUMO (eV) f 2.49 2.20 2.06 2.69 2.79 2.92
a) Data in parentheses are calculated values (see Table S1). b) Experimental data were determined from the
emission onset. c) E0-0(3CT) = E0-0(1CT) – ΔEST, where ΔEST was calculated using equation (6). d) Determined
from the highest energy peak of the phosphorescence spectrum in toluene at 77K. e) Determined from the highest
energy peak of the phosphorescence spectrum at 10K. f) Obtained from the HOMO value minus the optical band
gap.
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Table S3. Photophysical data for PXZ-DPS and DMAC-DPS in various solvents at room temperature.
compound solvent λmax, em
(nm) F
τF
(ns)
kF
(×107 s-1) TADF
τTADF
(μs)
kTADF
(×105 s-1)
ΔEST a
(eV)
PXZ-DPS
toluene 507 0.22 15 1.47 0.59 2.5 2.4 0.08
dioxane 524 0.16 19 0.84 0.32 1.5 2.1 0.07
chloroform 539 0.12 16 0.75 0.17 0.8 2.1 0.06
acetone 577 0.02 4.3 0.47 0.01 0.23 0.4 0.09
DMAC-DPS
toluene 460 0.16 20 0.80 0.64 7.1 0.9 0.09
dioxane 470 0.18 21 0.86 0.62 4.7 1.3 0.08
chloroform 496 0.18 21 0.86 0.62 2.3 2.7 0.06
acetone 520 0.13 20 0.65 0.46 1.4 3.3 0.05
a) Calculated using equation (6).
Figure S3. Photoluminescence spectra of (a) PXZ-DPS and (b) DMAC-DPS in various solvents at 300 K.
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Figure S4. Photoluminescence spectra of (a) PPZ-DPO, (b) PPZ-3TPT, (c) PPZ-4TPT, (d)
PPZ-DPS, (e) PXZ-DPS and (f) DMAC-DPS in toluene at 300 K and their phosphorescence
spectra (delayed by 10 ms) in toluene at 77 K.
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Figure S5. Streak image of a mCP film doped with 10 wt% of (a) PPZ-DPO, (b) PPZ-3TPT, (c) PPZ-4TPT, (d) PPZ-DPS, (e) PXZ-DPS and (f) DMAC-DPS at 300 K. The red shift of the delayed emission band with respect to the prompt emission band for the PPZ-DPS-doped film may be explained by the red-edge effect,17 which has also been observed in some TADF compounds with a ΔEST of around 0.3–0.5 eV,18 and some Cu(I) complexes doped into hosts with low triplet energy.19
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Figure S6. Plot of the natural logarithm of the rate of internal conversion between S1 and S0 states (kIC) versus emission energy (Eem) for PPZ-DPO, PPZ-DPS, PXZ-DPS and DMAC-DPS in various solvents at RT (Table S3). Herein, kIC is given by the formula = kF/(kF+kIC), and Eem is determined from the emission peak. This figure clearly shows that kIC increases exponentially when the emission energy is less than 2.5 eV and then decreases. This is in accordance with the energy gap law,20 which has also been applied to some Cu(I) phenanthroline complexes.21 If bimolecular processes are neglected in dilute solution, the contributions of kIC(S1-S0) and kISC(T1-S0) (see Fig. 1c) to the observed nonradiative rate constant (knr,obs) can be described as a Boltzmann average.22 Because kIC is generally 4–8 orders of magnitude greater than kISC with a similar energy gap for heavy atom-free aromatic compounds,20 knr,obs of these TADF emitters with a small ΔEST (< 0.1 eV) is determined mostly by kIC(S1-S0).
4. The lowest triplet energy level of DPEPO
Figure S7. (a) Photoluminescence spectra of DPEPO in CHCl3 at 300 and 77 K. (b) Streak image of a DPEPO neat film at 10 K.
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5. The comparison between DMAC-DPS and FIrpic
Figure S8. Comparison of the EL spectra (a), EQE-current density characteristics (b), current density-voltage characteristics (c), and luminance-voltage characteristics (d) of OLEDs with structure II containing FIrpic and DMAC-DPS.
Figure S9. Photoelectron yield spectra of neat films of DMAC-DPS and FIrpic.
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