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Supporting Information

Enhanced Proportion of Radiative Exciton in Non-doped

Electro-fluorescence Generated From Imidazole Derivative

with Orthogonal Donor-acceptor Structure

Shitong Zhang,a Weijun Li,a Liang Yao,a Yuyu Pan,a Fangzhong Shen a,b, Ran Xiaoa, Bing Yang*a,b and Yuguang Ma*a,c aState Key Laboratory of Supramolecular Structure and Materials,Jilin University, Changchun, 130012, P. R. China. Fax: +86 431 5168480; Tel: +86 431 5168480; bCollege of Chemistry, Jilin University, Changchun, 130012, P.R. China cInstitute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China. E-mail: [email protected], [email protected];

CONTENTS

S-1 General Methods

S-2. Detailed Synthesis of TPM and TPMCN

S-3. Supplementary photoluminancent properties

S-4. The solvatochromic Lippert-Mataga model

S-5 OLED Performances

S-6 Detailed TDDFT calculations

Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013

mailto:[email protected]

mailto:[email protected]

S-1 General Methods General: All of the reagents and solvents used for the syntheses are purchased from Aldrich or Acros and used as received. The 1H NMR spectra are recorded on AVANCZ 500 spectrometers at 298 K by utilizing deuterated dimethyl sulfoxide (DMSO) as solvents and tetramethylsilane (TMS) as a standard. The compounds are characterized by a Flash EA 1112, CHNS-O elemental analysis instrument. The MALDI-TOF-MS mass spectra are recorded using an AXIMA-CFRTM plus instrument. Photophysical: UV-vis absorption spectra are recorded on a UV-3100 spectrophotometer. Fluorescent spectra are measured with a RF-5301PC. PL efficiencies in solutions are measured with a UV-3100 and a RF-5310PC, relative to quinene solfate. Lifetimes are measured with a FLS-980 on an EPL-375 optical laser. PL efficiencies in films are measured with a Gliden Fluorescence System.

DFT Calculations: All DFT calculations are carried out under Gaussian 09_B.01 package on a cluster. The ground states are calculated at b3lyp/6-31g(d, p) level and the excited states at m062x/6-31g(d, p) level. OLED Fabrications and Performances: The EL devices are fabricated by vacuum deposition of the materials at 5×10-6torr. onto PEDOT:PSS modified ITO glass. All of the organic layers are deposited at a rate of 3.0 Å s-1. The cathode is deposited with LiF (1 nm) at a deposition rate of 0.1 Å s-1and then capping with Al metal (100 nm) through thermal evaporation at a rate of 4.0 Å s-1.The electroluminescence (EL) spectra and Commission Internationale De L’Eclairage (CIE)coordination of these devices are measured by a PR650 spectra scan spectrometer. The luminance-current and density-voltage characteristics are recorded simultaneously with the measurement of the EL spectra by combining the spectrometer with a Keithley model 2400 programmable voltage-current source. All measurements are carried out at room temperature under ambient conditions.

S-2. Detailed Synthesis of TPM and TPMCN a)4-Diphenylamino-benzaldehyde(TPA-CHO) A 61mmol(15g) triphenylamine in 15ml dehydrated DMF solution is added in a clean 250ml flask, stirred for 20min in a ice water bath to cool down to 5℃. Next, a 320mmol(30ml) POCl3 and 30ml dehydrated DMF mixture is carefully added dropwise into the reaction system, then move to a 35℃ oil bath and refluxed for 18h. The reaction liquid is carefully added into 400g trash ice and the solid product is filtrated, dissolved in CHCl3 and dried in MgSO4 overnight, purified by column layer chromatography and 8.6g(31mmol) white dry product is obtained, yield 50%. This product is used directly for the next step without further purifi cation and characterization. MS(ESI): MW 273.3, m/z=273.1(M+) .1H-NMR (500MHz, DMSO): 8.94 (d, J =8.4 Hz, 1H), 8.89 (d, J =8.4 Hz, 1H), 8.69 (d, J =8.0 Hz, 1H), 7.79 (t, J =7.4 Hz, 1H, ), 7.77–7.68 (m, 6H,), 7.58 (m, 3H,), 7.52 (d, J =8.4 Hz, 2H,), 7.35 (t, J =7.7 Hz, 1H), 7.09 (d, J =8.3 Hz, 1H).


b)Diphenyl-[4-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)-phenyl]-amine(TPM) A mixture of 2.0mmol(546mg)TPA-CHO, 2.0mmol(410mg)phenanthrenequinone, 8.0mmol(7.3ml) phenylamine and 10mmol(740mg) ammonium acetate with 15 ml acetic acid is added into a clean 100ml flask and refluxed under N2 in a 120℃ oil bath for 2h. After cooled down, the solid product is filtrated and ished with 30ml 1:1 water/acetic acid and 30ml water successively, dissolved in CHCl3and dried in MgSO4 overnight, purified by thin layer chromatography and 730mg(1.36mmol) pure dry white product is obtained, yield 68%.MS(ESI): MW 537.7, m/z=538.0(M+) . 1H-NMR (500MHz, DMSO):δ8.92(d, J=7.9Hz, 1H), 8.87(d, J=8.3Hz, 1H), 8.67(d, J=7.9Hz, 1H), 7.83.-7.69(m, 7H), 7.58(t, 1H), 7.47(d, J=8.8Hz, 2H), 7.39-7.29(m, 5H), 7.11(t, J=7.4Hz, 2H), 7.05(t, J=7.7Hz, 5H), 6.83(d, J=8.8Hz, 2H). Elemental Analysis: calculated for C39H27N3: C,87.12; H, 5.06; N, 7.82; found: C, 86.82; H, 5.24; N, 7.53. c)4-(2-(4-(diphenylamino)phenyl)-1H-phenanthro[9,10-d]imidazol-1-yl)benzonitrile(TPMCN) A mixture of 2.0mmol(546mg) TPA-CHO, 2.0mmol(410mg) phenanthrenequinone, 8.0mmol(944mg) 4-Amino-benzonitrile and 10mmol(740mg) ammonium acetate with 15 ml acetic acid is added into a clean 100ml flask and refluxed under N2 in a 120℃ oil bath for 2h. After cooled down, the solid product is filtrated and ished with 30ml 1:1 water/acetic acid and 30ml water successively, dissolved in CHCl3 and dried in MgSO4 overnight, purified by thin layer chromatography and 830mg(1.47mmol) pure dry bright yellow product is obtained, yield 74%. MS(ESI): MW 562.7, m/z=563.4M+) . 1H-NMR (500MHz, DMSO): δ 8.95 (d, J=8.2, 1H), 8.90 (d, J=8.7, 1H), 8.71 – 8.65 (m, 1H), 8.24 – 8.17 (m, 2H), 8.03 – 7.97 (m, 2H), 7.79 (t, J =7.5, 1H), 7.71 (t, J =7.7, 1H), 7.58 (t, J =7.1, 1H), 7.45 – 7.40 (m, 3H), 7.40 – 7.33 (m, 4H), 7.14 (dd, J =10.6, 4.2, 2H), 7.07 (dd, J =8.5, 1.1, 2H), 7.04 (d, J =7.4, 5H), 6.90 – 6.84 (m, 2H). Elemental Analysis: calculated for C40H26N4: C, 85.38; H, 4.66; N, 9.96; found: C, 85.63; H, 4.63; N, 9.96. S-3. Supplementary photoluminescent properties S-3-1 UV-VIS & PL Spectra of TPM and TPMCN in films.


S-3-2 Lifetime measurement of TPM and TPMCN on the EPL-375 optical laser (Wavelength 378.8nm; Pulse Width 68.9ps).

S-3-3 PL at 77K and phosphorescence in THF of TPM and TPMCN. The energy gap of S1 and T1 of TPM and TPMCN are 530 meV and 338 meV, respectively. The large energy gap blocked the TADF channel in both materials.

S-4. The solvatochromic Lippert-Mataga model

The Lippert-Mataga model is estimated according to Equation 1 as below.

ℎ𝑐(νa − 𝜈𝑓) = ℎ𝑐(ν𝑎0 − ν𝑓0) + 2�𝜇𝑒−𝜇𝑔�2

𝑎03 𝑓(𝜀,𝑛) (1)

Take differential on both sides of the equation 1, we got

𝜇𝑒 = 𝜇𝑔 + {ℎ𝑐𝑎03

2· �𝑑(νa−𝜈𝑓)

𝑑𝑓(ε,𝑛) �}1/2 (2)


where h is the Plank constant, c is the light speed in vacuum, 𝑓(ε,𝑛)is the orientational

polarizability of solvents and 𝑓 (ε,𝑛)=� 𝜀−12𝜀+1

− 𝑛2−12𝑛2+1

�,ν𝑎0 − ν𝑓0is the Stokes shifts when f is

zero, a0is the solvent Onsager cavity radius, μe and μg are dipole moments of excited-state and ground-state, respectively. ε is the solvent dielectric constant and n is the solvent refractive index. a0 and μg are estimated at the level of b3lyp/6-31g(d,p)from Gaussian09 package, which are 0.653nm and 1.57D, respectively. For TPM, a0 and μg are estimated as 0.663nm and 4.18D, respectively. Raw data for TPM and TPMCN are listed as below. TPM

Solvents f(ε,n) λa（nm） λf（nm） va - vf（cm-1）

Hexane 0.0012 360 394 2397.06712 Triethylamonia 0.048 362 396 2371.78414 n-Butylether 0.096 363 396 2295.68411 Ether 0.167 365 413 3184.18521 Ethylacetate 0.2 360 418 3854.33280 THF 0.21 360 413 3564.70272 Acetone 0.284 358 417 3952.14555 Acetonitrile 0.305 350 426 4303.59937

TPMCN

Solvents f(ε,n) λa（nm） λf（nm） va - vf（cm-1）

Hexane 0.0012 360 440 5050.50505 Triethylamonia 0.048 365 447 5025.89562 n-Butyl Ether 0.096 365 452 5273.36647 Isopropyl Ether 0.145 365 455 5419.2383 Ether 0.167 365 460 5658.12984 Ethyl Acetate 0.2 362 476 6615.90603 THF 0.21 360 480 6944.44444 Dichloromethane 0.217 361 487 7166.95012 DMF 0.276 362 512 8093.05939 Acetone 0.284 358 503 8052.24519 Acetonitrile 0.305 350 518 9266.40927


S-5 OLED Performances

S-5-1 TPM and TPMCN J-V-L curves.

S-5-2 Electroluminance under different current densities in TPMCN . Good linear relationship is observed that no TTA process exists in the EL device.

S-5-3 PL and EL luminances of TPM and TPMCN.


S-5-4 Device performances of TPM and TPMCN. The device structure is described in the article as ITO/PEDOT:PSS(40nm)/NPB(50nm)/Emitter(30nm)/TPBI(40nm)/LiF(0.5nm)/Al(120nm).

Emitter Von(V) Max LE(cd/A)

Max PE(lm/W)

CIE(x,y) Max Luminance(cd/m2)

Max EQE(%)

PLE(%) Max

EUE(%)

TPM 4 0.4 0.86 0.18,0.14 827 1.05 35 16

TPMCN 3.5 2.69 1.96 0.15,0.18 6483 2.18 13 85

S-5-5 Performances other devices prepared for TPM and TPMCN.

Structure* Von(V) Max

LE(cd/A)

Max

PE(lm/W) CIE(x,y)

Max

Luminance(cd/m2)

Max

EQE

(%)

PLE

(%)

Max

EUE(%)

a1 3.6 2.67 1.44 (0.16,0.20) 10310 1.73 13 67

a2 3.0 1.1 0.6 (0.17,0.14) 1875 1.1 35 16

b1 3.8 1.69 1.05 (0.15,0.19) 9670 1.22 13 47

c1 3.8 1.31 0.98 (0.16,0.17) 5982 1.13 13 42

* 1 for data of TPMCN, 2 for data of TPM. The device structures are: a) ITO/PEDOT:PSS(40nm)/NPB(80nm)/TCTA(5nm)/TPMCN(20nm)/TPBi(40nm)/LiF(0.5 nm)/Al(120nm) b) ITO/PEDOT:PSS/NPB(50nm)/TCTA(6nm)/CBP: TPMCN (6%)(30nm)/TPBi(40nm)/ LiF(0.5nm)/Al(120nm) c) ITO/PEDOT:PSS/NPB(40nm)/TAPC(5)/CBP: TPMCN (10%)(30nm)/TPBi(40nm)/ LiF(0.5 nm)/Al(120 nm). The doped films doesn't show higher PLE, indicates that the low PLE in TPMCN is not due to the aggregation quenching. ** Additionally, Zhang Y et.al. also reported a different device structure for TPM, and got a 19% max EUE, which is not above the 25% limit, either.[1]

S-6 Detailed TDDFT calculations

S-6-1 Calculated energy level results under Gaussian09_B.01 package, td-m062x/6-31g(d,p) level VS experimental data is listed as below. We choose data in hexane in comparison to the simulated vaccum data because hexane is weak enough in polarity (f=0.0012). UV hexane(nm) UV M062X(nm) PL hexane(nm) PL m062x(nm)

TPMCN 360 340 440 434

TPM 350 322 390 381


S-6-2 TDDFT analysis involving energy levels, transition dipole moments and natural transition orbital (NTO) .

Herein, we found in TPMCN, the energy level of S1 and T3 are very close (3.6566eV and 3.6518eV, respectively) , and they both show obvious CT character from NTO. Through the CT channel, triplet excitons can be converted to singlet excitons before populated on the T1 state, avoided the process of concentrate quenching, and enhanced the EUE in electroluminescence. On the other hand, though such close energy level can also be found in TPM, CT characters are not found in any energy states from NTO. The LE-like state character makes TPMCN an underperformer in singlet-triplet conversion, and poor performance in EL devices. Detailed NTO of TPM and TPMCN are listed below, respectively, as a reference. TDDFT Calculated energy levels, dipole moments and oscillator strengths of TPM and TPMCN are listed as below, respectively.

TPM

States Energy(eV) Transition Dipole Moments(Debye)

Oscilator Strength

States Energy(eV) Transition Dipole Moments(Debye)

S1 3.8501 6.02 1.1687 T1 3.0359 4.11 S2 4.1786 7.27 0.0297 T2 3.4252 5.79 S3 4.3943 3.26 0.0209 T3 3.67 4.28 S4 4.4772 5.62 0.0560 T4 3.7493 7.76 S5 4.5187 6.45 0.2283 T5 3.8523 3.71 S6 4.6416 5.20 0.0089 T6 3.9799 3.71 S7 4.7822 3.30 0.0196 T7 4.0765 4.98 S8 4.8783 3.00 0.0491 T8 4.2744 3.86 S9 5.0006 1.47 0.0463 T9 4.2791 3.80 S10 5.0283 4.63 0.0195 T10 4.3156 2.52


TPMCN

States Energy(eV) Dipole Moments(Debye)

Oscilator Strength

States Energy(eV) Dipole Moments(Debye)

S1 3.6566 12.8 0.2327 T1 3.0333 3.40 S2 3.9257 5.72 0.8902 T2 3.404 3.73 S3 4.2001 5.43 0.0362 T3 3.6518 9.68 S4 4.3661 5.28 0.0082 T4 3.7025 2.46 S5 4.4527 12.1 0.0250 T5 3.776 4.70 S6 4.5452 6.50 0.0200 T6 3.8315 2.20 S7 4.567 3.77 0.2099 T7 3.9044 5.78 S8 4.5954 9.14 0.0019 T8 3.9966 2.70 S9 4.7865 15.1 0.1354 T9 4.0954 0.53 S10 4.9108 1.78 0.0698 T10 4.2638 3.22 The S1 to S10 and T1 to T10 NTO of TPM and TPMCN are illustrated as below, respectively.


Reference [1] Y Zhang, Q Tong, et al. Chem. Mater. 2012, 24, 61−70.


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