Benzoselenadiazole-based donor-acceptor small molecule: Synthesis, aggregation-induced emission and electroluminescence

Article abstract of DOI:10.1016/j.dyepig.2017.10.020

Several tetraphenylethene and triphenylamine decorated donor-acceptor (D-A) benzoselenadiazole derivatives with aggregation-induced emission (AIE) features were synthesized and characterized. The photophysical, thermal, electrochemical and electroluminesc

Full text of DOI:10.1016/j.dyepig.2017.10.020

Accepted Manuscript
Benzoselenadiazole-based donor-acceptor small molecule: Synthesis, aggregation-
induced emission and electroluminescence
Aihui Liang, Han Wang, Yi Chen, Xiaoyan Zheng, Tian Cao, Xiulan Yang, Ping Cai,
Zhiping Wang, Xiaowen Zhang, Fei Huang
PII:
S0143-7208(17)31939-3
10.1016/j.dyepig.2017.10.020
DYPI 6318
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 12 September 2017
Revised Date: 12 October 2017
Accepted Date: 12 October 2017
Please cite this article as: Liang A, Wang H, Chen Y, Zheng X, Cao T, Yang X, Cai P, Wang Z, Zhang
X, Huang F, Benzoselenadiazole-based donor-acceptor small molecule: Synthesis, aggregation-induced
emission and electroluminescence, Dyes and Pigments (2017), doi: 10.1016/j.dyepig.2017.10.020.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Graphical abstracts
Se
N
N
TPE-Se-TPE
TPA-Se-TPE
TPA-Se-TPA
1.5
1.2
0.9
0.6
0.3
0.0
TPE-Se-TPE
TPA-Se-TPE
TPA-Se-TPA
3
2
1
0
TPE-Se-TPE
Se
N
N
N
TPE-Se-TPE
Se
N
N
N
N
0
50
100
150
200
0
20
40
60
80
2
Current density(mA/cm )
Water fraction(vol%)
TPA-Se-TPA

ACCEPTED MANUSCRIPT
Benzoselenadiazole-based Donor-Acceptor Small Molecule: Synthesis,
Aggregation-Induced Emission and Electroluminescence
Aihui Liang,a* Han Wang,a Yi Chen,a Xiaoyan Zheng,c Tian Cao,a Xiulan Yang,a
Ping Cai,b* Zhiping Wang,a Xiaowen Zhangb* and Fei Huangd*
aCollege of Chemistry and Chemical Engineering, Jiangxi Normal University,
Nanchang 330022, P. R. China. E-mail: lah14god@163.com.
bSchool of Materials Science and Engineering & Guangxi Key Laboratory of
Information Materials, Guilin University of Electronic Technology, Guilin 541004, P.
R. China. E-mail: caiping@guet.edu.cn
cDepartment of Chemistry, The Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong.
dState Key Laboratory of Luminescent Materials and Devices, Institute of Polymer
Optoelectronic Materials and Devices, South China University of Technology,
Guangzhou 510640, P. R. China. E-mail: msfhuang@scut.edu.cn.
1 / 29

ACCEPTED MANUSCRIPT
Abstract: Several tetraphenylethene and triphenylamine decorated donor-acceptor
(D-A) benzoselenadiazole derivatives with aggregation-induced emission (AIE)
features were synthesized and characterized. The photophysical, thermal,
electrochemical and electroluminescent (EL) properties, as well as the AIE property
of the resulting luminogens are discussed. All the luminogens are soluble in common
o
organic solvents and show high thermal stability with a Td of 399-460 C. The
absolute photoluminescence quantum yield in the solid state ranged from 14.2% to
36.5%. The D–A structures of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA enable
them to have aggregation-caused quenching (ACQ) plus aggregation-induced
emission enhancement (AIEE) effects dominated by the twisted intramolecular
charge-transfer (TICT) and restriction of intramolecular rotations (RIR), respectively.
The best device performances were obtained from TPA-Se-TPE with a maximal
luminous efficiency of 2.91 cd/A and the maximal brightness is 5855 cd/m2. This is
the first report of benzoselenadiazole-based fluorophore with an AIE feature for
organic electronics application.
Keywords: orgainc light-emitting diode; aggregation-induced emission;
benzoselenadiazole; tetraphenylethene; triphenylamine
2 / 29

ACCEPTED MANUSCRIPT
1. Introduction
Organic light-emitting diodes (OLEDs) have attracted considerable attention due to
their potential applications in flat-panel displays and solid-state lighting [1-9], with
tremendous advances such as thin-film formation, high contrast, low weight, fast
response, wide-view angle and low power consumption. Organic optoelectronic
functional molecules are usually used as films or aggregates [10-12]. However,
traditional luminophores generally suffer from the aggregation-caused quenching
(ACQ) effect: they are highly emissive in dilute solution but become weakly or non-
emissive in high concentration or condensed phases like aggregates or solid state due
to their planar conjugated structures. The ACQ effect has reduced the performance of
traditional luminophores when used in optoelectronic devices. In order to alleviate
this negative effect, various approaches have been adopted, such as physical doping or
chemical modification with bulky groups [13-20]. Nevertheless, it is difficult to
precisely control the doping concentration and avoid the phase separation between the
host and the guest during usage in the physical doping system. Whereas, in the latter
chemical modification case, tedious synthetic procedures and a lengthened operating
time are also involved. In other words, these methods met with limited success. The
discovery of aggregation-induced emission (AIE) molecular systems which exhibit
either no or weak luminescence in solution but exhibit strong luminescence in the
aggregated state supplies a novel method to solve the problem of ACQ [21, 22].
Among the reported AIE fluorophores, tetraphenylethene (TPE) is a classical
luminogen with intriguing AIE characteristic [23, 24]. TPE and TPE-based materials
have received the most attention owing to their well-defined AIE properties, high
solid-state fluorescence quantum yields and ease of synthesis, which has been widely
used in optic- and electro-active materials due to its electron-donating property and

ACCEPTED MANUSCRIPT
propeller-like molecular structure [25]. The triphenylamine (TPA) moiety is well
known for its luminescence properties, electron-donating ability, and hole
transporting capability. Recently, much work incorporating the TPA moiety into the
construction of new AIE luminogens (AIEgens) has been conducted [26-28]. The
three phenyl rotors and the nonplanar structure of TPA make it an ideal building block
for AIEgens. The rotational motions of the phenyl rings in TPA aid in dissipating
excited-state energy in the solution state and assist in restriction of intramolecular
rotations (RIR) in the solid state. Its twisted structure helps reduce the formation of
destructive intermolecular π−π stacking interactions.
The benzoselenadiazole is an excellent acceptor with good electron-withdrawing
ability, which has a higher electron affinity than benzothiadiazole, thus using
benzoselenadiazole as an acceptor is conductive to promoting intramolecular charge-
transfer (ICT) process and constructing D-A materials for OLEDs [29-31]. In this
manuscript, we have synthesized three donor-acceptor benzoselenadiazole based
small molecules by Suzuki coupling reaction. The photophysical, thermal,
electrochemical and electroluminescent (EL) properties, as well as the AIE property
of the resulting luminogens are discussed. All luminogens show high thermal stability
o
with a Td nearly or above 400 C. The best device performances were obtained from
TPA-Se-TPE with a maximal luminous efficiency of 2.91 cd A-1 and the maximal
brightness is 5855 cd m-2. This is the first report of a benzoselenadiazole-based
fluorophore with an AIE feature which was successfully applied to OLEDs.
2. Experimentals
2.1. Materials
N-phenyl-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)benzenamine
(7) was prepared according to the reported procedures [32]. All reactions were
4 / 29

ACCEPTED MANUSCRIPT
performed under nitrogen. Tetrahydrofuran (THF) was distilled under normal pressure
from sodium benzophenone ketyl under nitrogen immediately prior to use. Other
solvents and chemicals were used without further purification unless otherwise stated.
Synthesis of 4,7-Dibromo-2,1,3-benzothiadiazole (1)[30]: A mixture of 2,1,3-
benzothiadiazole (13.6 g, 0.1 mol) in 45% hydrobromic acid (30 mL) was heated
under reflux with stirring while 48 g (0.3 mol, 15.3 mL) of bromine was added
slowly. The reaction mixture became a suspension of solid in hydrobromic acid and
15 mL of hydrobromic acid was added, then the mixture was refluxed for another 2.5
h. After cooling to room temperature, the precipitate formed and collected, washed
with water, then recrystallized from chloroform to give yellow needle crystals (26.8 g,
o
1
13
91%). mp 186-188 C. H NMR (400 MHz, CDCl3) δ (ppm): 7.73 (s, 2H). C NMR
(100 MHz, CDCl3) δ (ppm): 153.34, 132.67, 114.31. Anal. Calcd for C6H2Br2N2S: C,
24.51; H, 0.69; N, 9.53. Found: C, 24.12; H, 0.72; N, 9.66.
Synthesis of 4,7-Dibromo-2,1,3-benzoselenadiazole (3)[30]: To a suspension of
4,7-dibromo-2,1,3-benzothiadiazole (1) (5.88 g, 20 mmol) in ethanol (190 mL),
sodium borohydride (14 g, 0.37 mol) was added portionwise at 0 °C, then the mixture
was stirred for 20 h at room temperature. After evaporation of the volatile solvent and
water (200 mL) was added, the mixture was extracted with dichloromethane (3×30
mL). The extract was dried over anhydrous magnesium sulfate and evaporated to
remove the solvents under vacuum. 3,6-Dibromo-1,2-phenylenediamine (2) (4.7 g)
was obtained as a pale yellow solid in 87% yield. The intermediate 2 was directly
used in the following procedure. A solution of selenium dioxide (1.17 g, 10.5 mmol)
in hot water (22 mL) was added to a solution of 2 (2.7 g, 10 mmol) in refluxing
ethanol (55 mL). The reaction mixture was heated under reflux for 2 h. After the
mixture had been cooled to room temperature, filtration of the yellow precipitates and
5 / 29

ACCEPTED MANUSCRIPT
recrystallization from ethyl acetate gave 4,7-dibromo-2,1,3-benzoselenadiazole (3)
(2.8 g) in 82% yield as golden yellow needles. 1H NMR (400 MHz, CDCl3) δ (ppm):
7.65 (s, 2H). mp 285-287 °C. 13C NMR (100 MHz, CDCl3) δ (ppm): 157.2, 132.1,
116.5. Anal. Calcd for C6H2Br2N2Se: C, 21.14; H, 0.59; N, 8.22. Found: C, 21.34; H,
0.92; N, 7.98.
Synthesis of 1-bromo-4-(1,2,2-triphenylvinyl)benzene (5) [33]: n-Butyllithium
(1.6 mol/L, 10 mmol) was added dropwise to a solution of diphenylmethane (1.77 g,
10.5 mmol) in anhydrous THF (50 mL) at 0 °C. The reaction mixture was stirred for
0.5 h, and then turned to red before (4-bromophenyl)phenylmethanone (3.38 g, 10
mmol) was added in one portion. The mixture was warmed to room temperature,
stirred for 6 h and then was poured into water while stirring. The mixture was
extracted with dichloromethane (3×50 mL) and the combined extracts were dried over
anhydrous MgSO4. The solvent was evaporated and the resultant crude alcohol 4
(containing excess diphenylmethane) was subjected to acid-catalyzed dehydration as
follows. Compound 4 was dissolved in toluene (50 mL) in a 100 mL Schlenk flask
fitted with a Dean-Stark trap. A catalytic amount of p-toluenesulfonic acid (342 mg,
1.8 mmol) was added and the mixture was refluxed for 3 h. After cooled to room
temperature, the toluene layer was washed with 10% aqueous NaHCO3 solution (2 ×
25 mL) and dried over anhydrous MgSO4. The solvent was evaporated under reduced
pressure the crude product was purified with column chromatography on silica gel
with petroleum ether/ dichloromethane (15:1) as eluent to afford a residue of 5 (1.2 g)
in yield of 63%. mp 216-218 °C. 1H NMR (400 MHz, CDCl3) δ (ppm): 7.25–7.20 (d,
J = 8.06 Hz, 2H), 7.17–7.08 (m, 9H), 7.07–6.99 (m, 6H), 6.94–6.87 (d, J = 8.14 Hz,
2H). 13C NMR (100 MHz, CDCl3), δ (ppm): 148.06, 143.19, 143.14, 143.09, 141.75,
6 / 29

ACCEPTED MANUSCRIPT
140.63, 134.72, 132.62, 131.21, 130.78, 130.69, 127.62, 127.54, 126.37, 126.23.
Anal. Calcd for C26H19Br: C, 75.92; H, 4.66. Found: C, 76.14; H, 4.52.
Synthesis
of
4,4,5,5-tetramethyl-2-(4-(1,2,2-triphenylvinyl)phenyl)-1,3,2-
dioxaborolane (6)[34]: To a solution of compound 5 (3.22 g, 10 mmol) in anhydrous
THF (15 mL), n-Butyllithium (1.6 mol/L, 7.5 mL, 12 mmol) was added dropwise at –
78 °C. The reaction mixture was stirred for 0.5 h before isopropoxyboronic acid
pinacol ester (2.5 mL, 12 mmol) was added in one portion. The mixture was warmed
to room temperature and stirred for 12 h. Then the mixture was poured into water
while stirring. The organic phase was separated and the aqueous phase was extracted
with dichloromethane (3×30 mL). The combined organic layers were dried over
MgSO4 and evaporated to remove the solvents under vacuum. The residue was
purified by column chromatography (petroleum ether/dichloromethane = 8/1) to
1
provide 6 (1.6 g) as white solid in 50% yield. mp 203-205 °C. H NMR (400 MHz,
CDCl3) δ (ppm): 7.54–7.52(d, J = 8.04 Hz, 2H), 7.09–7.07(m, 8H), 7.04–6.98 (m,
9H). 13C NMR (100 MHz, CDCl3), δ (ppm): 148.26, 143.49, 143.44, 143.39, 141.75,
140.73, 134.92, 132.82, 131.30, 130.98, 130.89, 127.71, 127.65, 126.66, 126.53,
84.11, 22.99. Anal. Calcd for C32H31BO2: C, 83.84; H, 6.82. Found: C, 83.06; H, 7.03.
Synthesis of TPE-Se-TPE: Pd(PPh3)4 (143 mg) was added to a mixture of 3 (340
mg, 1.0 mmol), 6 (1.14 g, 2.5 mmol), THF (50.0 mL) and 2.0 M K2CO3 solution (10.0
mL). The mixture was degassed and heated under reflux with vigorously stirring for
24 h under N2 flow protection. After cooled to room temperature, the mixture was
poured into water and extracted with dichloromethane (3×30 mL). The combined
organic layers were collected, dried over anhydrous MgSO4, filtered and evaporated
to remove the solvent. The resulted crude product was chromatographed on a silica
gel column (petroleum ether/dichloromethane = 10/1) to give TPE-Se-TPE (565 mg)
7 / 29

ACCEPTED MANUSCRIPT
in a yield of 67%. 1H NMR (400 MHz, CDCl3) δ (ppm): 7.68−7.66 (d, J = 8.28 Hz,
4H), 7.56 (s, 2H), 7.19−7.16 (d, J = 8.32 Hz, 4H), 7.13−7.09 (m, 26H), 7.06−7.04 (m,
4H). 13C NMR (100 MHz, CDCl3) δ (ppm): 159.66, 143.80, 143.68, 143.62, 141.42,
140.57, 135.97, 134.37, 131.51, 131.38, 128.65, 127.88, 127.73, 127.65, 126.59,
126.51. Anal. Calcd. for C58H40N2Se: C, 82.55; H, 4.78; N, 3.32; Found: C, 82.59; H,
7.75; N, 3.39. MALDI-TOF (m/z): calcd for TPE-Se-TPE: 844.236, found 844.239.
Synthesis of TPA-Se-TPE: N-phenyl-N-(4-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)phenyl)benzenamine (7) (1.11 g, 3.0 mmol), 3 (1.12 g, 3.0 mmol),
Pd(PPh3)4 (172 mg), THF (70 mL) and 2.0 M K2CO3 solution (15.0 mL) were added
in a 150 mL two-necked round-bottomed flask. The mixture was refluxed for 24 h
under argon atmosphere. After the mixture had been cooled to the room temperature,
the mixture was poured into brine and extracted twice with dichloromethane. The
combined organic layers were dried over MgSO4 and the solvent was removed. The
crude product was purified with column chromatography (silica gel, petroleum
ether/dichloromethane (20/1) as eluent) to yield 894 mg (59%) of 8 as a light yellow
solid. 1H NMR (400 MHz, CDCl3) δ (ppm): 7.96−7.94 (d, J = 7.52 Hz, 1H),
7.83−7.81 (d, J = 8.68 Hz, 2H), 7.52−7.50 (d, J = 7.52 Hz, 1H), 7.37−7.33 (t, J = 7.90
Hz, 4H), 7.10−7.06 (m, 8H).
Pd(PPh3)4 (120 mg) was added to a mixture of 8 (1.05 g, 1.77 mmol), 6 (959 mg,
2.1 mmol), THF (50.0 mL) and 2.0 M K2CO3 solution (10.0 mL). The reaction
mixture was degassed and heated under reflux with vigorously stirring for 24 h under
N2 flow protection. After cooling to room temperature, the mixture was poured into
water and extracted with dichloromethane (3×30 mL). The combined organic layers
were collected, dried over anhydrous MgSO4, filtered and evaporated to remove the
solvent. The resulted crude product was chromatographed on a silica gel column
8 / 29

ACCEPTED MANUSCRIPT
(petroleum ether/dichloromethane = 12/1) to give TPA-Se-TPE (1.09 g) in a yield of
1
82%. H NMR (400 MHz, CDCl3) δ (ppm): 7.88−7.86 (d, J = 8.72 Hz, 2H),
7.78−7.76 (d, J = 8.32 Hz, 2H), 7.69−7.64 (t, J = 9.28 Hz, 2H), 7.37−7.33 (t, J = 7.92
Hz, 4H), 7.19−7.03 (m, 23H), 7.01−6.99 (d, J = 7.96 Hz, 2H). 13C NMR (CDCl3, 100
MHz) δ (ppm): 147.51, 131.52, 131.38, 130.21, 129.36, 128.62, 127.73, 127.65,
126.51, 124.89, 123.27, 122.85, 122.81, 122.07. Anal. Calcd. for C50H35N3Se: C,
79.35; H, 4.66; N, 5.55; Found: C, 79.42; H, 4.73; N, 5.59. MALDI-TOF (m/z): calcd
for TPA-Se-TPE: 757.2, found 757.212.
Synthesis of TPA-Se-TPA: Pd(PPh3)4 (143 mg) was added to a mixture of 3 (340
mg, 1.0 mmol), 7 (928 mg, 2.5 mmol), THF (60.0 mL) and 2.0 M K2CO3 solution
(10.0 mL). The mixture was degassed and heated under reflux with vigorously stirring
for 24 h under N2 flow protection. After cooled to room temperature, the mixture was
poured into water and extracted with dichloromethane (3×30 mL). The combined
organic layers were collected, dried over anhydrous MgSO4, filtered and evaporated
to remove the solvent. The resulted crude product was chromatographed on a silica
gel column (petroleum ether/dichloromethane = 15/1) to give TPA-Se-TPA (509 mg)
1
in a yield of 76%. H NMR (400 MHz, CDCl3) δ (ppm): 7.80−7.78 (d, J = 8.64 Hz,
4H), 7.59 (s, 2H), 7.31−7.27 (t, J = 7.86 Hz, 8H), 7.21−7.18 (m, 12H), 7.07−7.04 (t, J
= 7.28 Hz, 4H). 13C NMR (CDCl3, 100 MHz) δ (ppm): 147.90, 147.56, 134.02,
131.72, 129.34, 127.91, 124.87, 123.24, 122.89. Anal. Calcd. for C42H30N4Se: C,
75.33; H, 4.52; N, 8.37; Found: C, 75.38; H, 4.56; N, 8.29. MALDI-TOF (m/z): calcd
for TPA-Se-TPA: 670.164, found 670.168.
2.2 Measurements and Characterization
1H and 13C NMR spectra were recorded on a Bruker 400 spectrometer operating
respectively at 400 and 100 MHz at room temperature. Chemical shifts were reported
9 / 29

ACCEPTED MANUSCRIPT
as δ values (ppm) relative to an internal tetramethylsilane (TMS) standard. Time-of-
flight mass spectrometry (TOF-MS) was carried out on a Bruker-autoflex III
smartbeam. Thermogravimetric analysis (TGA) was carried out on a Diamond
TG/DTA instrument under a nitrogen atmosphere at a heating rate of 20 oC min-1 and
Td was reported as the temperatures at 5% weight losses. UV-vis absorption spectra
were measured on a HP 8453 spectrophotometer. PL spectra were recorded on an
Instaspec IV CCD spectrophotometer (Oriel Co.) under 325 nm excitation of a HeCd
laser. Cyclic voltammetry was carried out on a CHI660A electrochemical workstation
in a solution of tetrabutylammonium hexafluorophosphate (Bu4NPF6) (0.1 M) in
acetonitrile at a scan rate of 50 mV/s at room temperature under the protection of
argon. A platinum electrode was used as the working electrode. A Pt wire was used as
the counter electrode, and a calomel electrode was used as the reference electrode.
The absolute photoluminescence quantum yield (ФPL) was measured with a
Hamamatsu absolute PL quantum yield spectrometer equipped with an integrating
sphere (Quantaurus-QY, C11347).
2.3 Theoretical Calculations
The geometries of both iridium complexes Y1 and Y2 at the gas phase were fully
optimized by the density functional theory (DFT) method at the 6-31G* basis set with
B3LYP functional [35, 36] without any symmetry constraints by using the Gaussian
09 software package [37].
2.4 OLEDs fabrication and measurements
The ITO-coated glass substrates were ultrasonically cleaned with deionized water,
acetone, detergent, deionized water, and isopropyl alcohol. Then an MoO3 hole
injection layer (2 nm) was obtained by thermal deposition under a vacuum of 4×10‒4
Pa. Then organic stacks of N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine
10 / 29

ACCEPTED MANUSCRIPT
(NPB, 50 nm), TPE-Se-TPE (or TPA-Se-TPE or TPA-Se-TPA) (20 nm) and 4,7-
diphenyl-1,10-phenanthroline (BPhen, 40 nm) served as hole transport layer, emitting
layer and electron transport layer, respectively, were sequentially layered by thermal
deposition under a vacuum of 4×10‒4 Pa. Finally, LiF (1 nm)/Al (100 nm) was served
as conventional bilayer cathode. The layer thickness and deposition rate were
monitored and controlled in situ by using an oscillating quartz thickness monitor. The
typical deposition rate of organic layer was 1‒2 Å/s while that of Al was 3‒5 Å/s. The
current density (J) and brightness (L) versus voltage (V) data were collected using a
Keithley 236 source meter and silicon photodiode. After typical encapsulation with
UV epoxy and cover glass, the devices were taken out from the dry box and the
luminance was calibrated by a PR-705 SpectraScan Spectrophotometer (Photo
Research) with simultaneous acquisitions of the EL spectra.
3. Results and discussion
3.1 Synthesis and Characterization
The synthetic routines to TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA are shown
in Scheme 1. The 4,7-Dibromo-2,1,3-benzoselenadiazole (3) was prepared in good
yield over three steps starting from the readily commercially available materials.
Firstly, 2,1,3-benzothiadiazole was brominized in HBr and recrystallized from
chloroform to give yellow solid 4,7-Dibromo-2,1,3-benzothiadiazole (1) in the yield
of 91%. Secondly, the compound 1 was reacted with NaBH4 at 0 °C to obtain 3,6-
dibromobenzene-1,2-diamine (2). Thirdly, the compound 2 was added in ethanol
solution containing selenium dioxide to produce the compound 3 with high yield [38].
After the lithiation of diphenylmethane, (4-bromophenyl)phenylmethanone was added
to the reaction mixture to generate the resultant alcohol 4, which underwent
dehydration in the presence of PTSA to form 5 in 63% yield. Treatment of 5 with n-
11 / 29

ACCEPTED MANUSCRIPT
butyllithium followed by reaction with isopropoxyboronic acid pinacol ester furnished
compound 6 [33]. The target products TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA
were synthesized by Suzuki coupling reaction of compound 3 with tetraphenylethene
boronic ester (6) and triphenylamine boronic ester (7). The chemical structures of
TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA were fully characterized by NMR
spectroscopy, elemental analysis and time-of-flight mass spectrometry (TOF-MS). All
target products are readily soluble in common organic solvents such as chloroform,
dichloromethane and THF at room temperature, but are insoluble in water.
Photophysical Properties
The photophysical properties of the resultant compounds TPE-Se-TPE, TPA-Se-
TPE and TPA-Se-TPA in neat film were investigated. The UV-vis absorption and
photoluminescence (PL) spectra of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA at
room temperature are shown in Figure 1. The UV–vis absorption spectra of the three
target compounds showed two distinct absorption peaks in THF solution: 330 nm and
433 nm for TPE-Se-TPE, 329 nm and 461 nm for TPA-Se-TPE, 323 nm and 475 nm
for TPA-Se-TPA. The peaks at short wavelength are attributed to the localized π–π*
transition; and the other peaks at longer wavelength are due to the intramolecular
charge transfer (ICT) transition between the donor and acceptor units. The compounds
TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA displayed the maximum PL emission
peaks in neat film at 552 nm, 615 nm and 624 nm, respectively. Compared to TPE-Se-
TPE, TPA-Se-TPE and TPA-Se-TPA exhibit much red-shifted emission with 63 nm
and 72 nm. This suggests that the higher energy transfer between the triphenyamine
unit and the benzoselenadiazole unit than that of the tetraphenylethene unit and the
benzoselenadiazole unit. The absolute photoluminescence quantum yields (ФPL) for
TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA in solid state are summarized in Table 1.
12 / 29

ACCEPTED MANUSCRIPT
The values of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA were recorded to be 14.2,
36.5 and 32.4%, respectively.
3.2 Electrochemical Properties and Theoretical Calculations
The electrochemical behavior of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA were
studied by cyclic voltammetry (CV) using ferrocene as the internal standard and the
results are listed in Table 1. The oxidization peaks with onset potentials of TPE-Se-
TPE, TPA-Se-TPE and TPA-Se-TPA at 0.45, 0.13 and 0.09 eV, respectively, could be
easily observed in the positive scan direction, which may be resulting from the
oxidation of selenium atom in the benzoselenadiazole unit, where the selenium is an
electron-rich atom and easy to be oxidized. The energy levels of the highest occupied
molecular orbital (EHOMO), determined by calculation from the empirical formula of
EHOMO = -(4.8 + Eox), are -5.25, -4.93 and -4.89 eV. Unfortunately, no clear reduction
waves of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA were observed despite many
attempts. The lowest unoccupied molecular orbital energy levels (ELUMO) had to be
calculated based on the equation of ELUMO = EHOMO + Eg, in which energy band gap
(Eg) was estimated from the UV-vis absorption threshold. The ELUMO of TPE-Se-TPE
is calculated to be -2.77 eV, while those of TPA-Se-TPE and TPA-Se-TPA are -2.61
eV and -2.65 eV. To further investigate the structure-property relationship of the
compounds TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA at the molecular level, the
geometrical and electronic structures of the resulting compounds were performed
using density functional theory, see details in theoretical calculations. The electron
density distributions of both HOMO and LUMO for TPE-Se-TPE, TPA-Se-TPE and
TPA-Se-TPA are illustrated in Figure 2. The LUMO distrubutions of TPE-Se-TPE,
TPA-Se-TPE and TPA-Se-TPA were mainly located in the benzoselenadiazole
moieties. While the HOMO distrubutions of TPE-Se-TPE and TPA-Se-TPA were
13 / 29

ACCEPTED MANUSCRIPT
mainly located in the whole molecular framework, HOMO distrubutions of TPA-Se-
TPE was mainly located in the triphenylamine moieties, which further indicated that
there really existed obvious ICT in TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA. The
calculated energies of HOMOs for TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA are
−5.15 eV, −4.89 eV and −4.78 eV, respectively. The corresponding energies of
LUMOs for TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA are −2.44 eV, −2.41 eV and
−2.37 eV, respectively. Based on the calculated HOMO and LUMO energies for these
target compounds, we found that the calculated HOMO–LUMO energy gap of TPE-
Se-TPE, TPA-Se-TPE and TPA-Se-TPA are 2.70 eV, 2.48 eV and 2.41 eV, which is
qualitatively consistent with the experimental results by CV measurement. The results
suggested that the more triphenylamine groups the energy band-gap is smaller, which
is in agreement with the photophysical properties.
3.3 Thermal Properties
The thermal stability of these compounds was evaluated by thermogravimetric
o
analysis (TGA) under a stream of N2 with a scanning rate of 20 C/min. Their TGA
curves are shown in Figure 3 and their degradation temperatures (Td) for 5% weight
loss are listed in Table 1. The recorded Td for TPE-Se-TPE, TPA-Se-TPE and TPA-Se-
TPA are 399, 406 and 460 oC, respectively. The data demonstrate that the resulting
compounds functionalized by tetraphenylethene or triphenylamine can possess good
thermal properties, which is desirable for the application in organic light-emitting
diodes.
3.4 Aggregation-induced emission performances
The AIE properties of the compounds TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA
were examined by studying the PL emission behaviour of their diluted mixtures in
THF/water under different water fractions. The aggregates were prepared by adding
14 / 29

ACCEPTED MANUSCRIPT
various fractions of ultra-pure water into the THF solutions. As shown in Figure 4,
TPA-Se-TPE emits at 615 nm in pure THF solution (10-5 mol L-1). When the water
fraction (fw) is inferior to 40%, the emission of TPA-Se-TPE weakened with a red-
shift of their peaks at the same time. Specifically, more than 95% of its fluorescence
intensity was quenched and a bathochromic shift of about 13 nm could be discerned at
fw of 40%. This may be attributed to the twisted intramolecular charge-transfer (TICT)
effect of TPA-Se-TPE in the gradually strengthened polar mixed solvent of THF/water
with a higher fraction of polar water [39-41]. Afterwards, the fluorescence intensity
promptly enhanced with a blue-shift of peaks and reached the maximum value at fw of
80% due to the aggregate formation. The mechanism of aggregation-induced emission
enhancement (AIEE) may be attributed to the restriction of intramolecular rotation
(RIR). The weaker emission of TPA-Se-TPE in the THF/water mixtures with fw of 90%
compared to that with fw of 80% is probably due to the difference in aggregate
morphology [42, 43]. The similar D–A structures of TPE-Se-TPE and TPA-Se-TPA
also enable them to have ACQ plus AIEE effects dominated by the TICT and RIR,
respectively (Figure S1, ESI†).
3.5 Electroluminescent Devices
To understand the electroluminescent properties of the compounds TPE-Se-TPE,
TPA-Se-TPE and TPA-Se-TPA, OLEDs were fabricated using them as emitting
layers in the configuration: ITO/MoO3/NPB/Emitting Layer/Bphen/LiF/Al. The EL
spectra of the TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA are shown in Figure 5.
The EL spectra of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA displayed yellow to
red emission with a maximal emitting peak at ca. 570 nm, 632 and 640 nm,
respectively, which are identical to the corresponding solid-state PL emission. The
Commission Internationale de L’Eclairage (CIE) coordinates of TPE-Se-TPE, TPA-
15 / 29

ACCEPTED MANUSCRIPT
Se-TPE and TPA-Se-TPA are located at (0.48, 0.51), (0.63, 0.37) and (0.65, 0.34)
respectively. Figure 6 shows the brightness–voltage characteristics (L–V) and the
luminous efficiency–current density (LE–J) for those devices from TPE-Se-TPE,
TPA-Se-TPE and TPA-Se-TPA, the relevant data are presented in Table 2. For the
device of TPE-Se-TPE, a turn-on voltage (Von) of 4.6 V, a maximal luminous
efficiency (LEmax) of 0.19 cd A-1 at a current density of 101 mA cm-2 and a maximum
luminance (Lmax) of 385 cd m-2 are achieved. For the device of TPA-Se-TPA, a Von of
3.5 V, a LEmax of 1.84 cd A-1 at a current density of 1.97 mA cm-2 and an Lmax of 2289
cd m-2 are achieved. Among these compounds, the device of TPA-Se-TPE exhibited
the highest device performance with a low Von of 3.2 V, a good LEmax of 2.91 cd A-1 at
a current density of 33.9 mA cm-2 and an Lmax of 5855 cd m-2. According to the
current density–voltage characteristics (J–V) (Figure S2, ESI†), it suggested that the
more triphenylamine groups in the molecule the carrier transporting is easier, which is
important to the electroluminescent properties. The EL performances for these
luminescent materials are in the order of TPE-Se-TPE < TPA-Se-TPA < TPA-Se-
TPE, which is identical to the order of ФPL in the solid state.
4. Conclusions
In summary, we have successfully synthesized three donor-acceptor luminogens,
TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA, by covalently binding electron-
donating TPA and TPE moieties to an electron-accepting benzoselenadiazole core via
a Suzuki coupling reaction. All the luminogens are soluble in common organic
o
solvents and show high thermal stability with a Td nearly or above 400 C. The
absolute photoluminescence quantum yield in the solid state ranged from 14.2% to
36.5%. The D–A structures of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA enable
them to exhibit ACQ plus AIEE effects dominated by the TICT and RIR,
16 / 29

ACCEPTED MANUSCRIPT
respectively. The best device performances were obtained from TPA-Se-TPE with a
Von of 3.2 V, LEmax of 2.91 cd A-1, EQE of 3.4% and Lmax of 5855 cd m-2. This is the
first report of benzoselenadiazole-based fluorophore with an AIE feature which was
successfully applied to OLEDs.
Acknowledgements
The work was financially supported by the National Natural Science Foundation of
China (No. 51763013, 51403088 and 61565003), the China Postdoctoral Science
Foundation (No. 2016M592111) and the Postdoctoral Science Foundation of Jiangxi
Province (No. 2016KY05).
References
[1] Tang CW, VanSlyke SA. Organic electroluminescent diodes. Appl Phys Lett
1987; 51: 913-15.
[2] Sasabe H, Toyota N, Nakanishi H, Ishizaka T, Pu YJ, Kido J. 3,3'-bicarbazole-
based host materials for high-efficiency blue phosphorescent OLEDs with
extremely low driving voltage. Adv Mater 2012; 24: 3212-7.
[3] D'Andrade BW, Forrest SR. White organic light-emitting devices for solid-state
lighting. Adv Mater 2004; 16: 1585-95.
[4] Burn PL, Lo S-C, Samuel IDW. The development of light-emitting dendrimers for
displays. Adv Mater 2007; 19: 1675-88.
[5] Kido J, Kimura M, Nagai K. Multilayer white light-emitting organic
electroluminescent device. Science (New York, N.Y.) 1995; 267: 1332-4.
[6] Duggal AR, Shiang JJ, Heller CM, Foust DF. Organic light-emitting devices for
illumination quality white light. Appl Phys Lett 2002; 80: 3470-2.
[7] Yook KS, Lee JY. Organic materials for deep blue phosphorescent organic light-
emitting diodes. Adv Mater 2012; 24: 3169-90.
17 / 29

ACCEPTED MANUSCRIPT
[8] Forrest SR. The road to high efficiency organic light emitting devices. Org
Electron 2003; 4: 3.
[9] Zou J, Wu H, Lam C-S, Wang C, Zhu J, Zhong C, Hu S, Ho C-L, Zhou G-J, Wu
H, Choy WCH, Peng J, Cao Y, Wong W-Y. Simultaneous Optimization of Charge-
Carrier Balance and Luminous Efficacy in Highly Efficient White Polymer Light-
Emitting Devices. Adv Mater 2011; 23: 2976-+.
[10] Friend RH, Gymer RW, Holmes AB, Burroughes JH, Marks RN, Taliani C,
Bradley DDC, Dos Santos DA, Bredas JL, Logdlund M, Salaneck WR.
Electroluminescence in conjugated polymers. Nature 1999; 397: 121-8.
[11] Liu X-M, Lin T, Huang J, Hao X-T, Ong KS, He C. Hyperbranched Blue to Red
Light-Emitting Polymers with Tetraarylsilyl Cores:ꢀ Synthesis, Optical and
Electroluminescence Properties, and ab Initio Modeling Studies. Macromolecules
2005; 38: 4157-68.
[12] Liu X-M, He C, Hao X-T, Tan L-W, Li Y, Ong KS. Hyperbranched Blue-Light-
Emitting Alternating Copolymers of Tetrabromoarylmethane/Silane and 9,9-
Dihexylfluorene-2,7-diboronic Acid. Macromolecules 2004; 37: 5965-70.
[13] Shao S, Ding J, Wang L, Jing X, Wang F. Highly Efficient Blue
Electrophosphorescent Polymers with Fluorinated Poly(arylene ether phosphine
oxide) as Backbone. J Am Chem Soc 2012; 134: 15189-92.
[14] Zou Y, Zou J, Ye T, Li H, Yang C, Wu H, Ma D, Qin J, Cao Y. Unexpected
Propeller-Like Hexakis(fluoren-2-yl)benzene Cores for Six-Arm Star-Shaped
Oligofluorenes: Highly Efficient Deep-Blue Fluorescent Emitters and Good Hole-
Transporting Materials. Adv Funct Mater 2013; 23: 1781-8.
[15] Li Z, Jiao B, Wu Z, Liu P, Ma L, Lei X, Wang D, Zhou G, Hu H, Hou X.
Fluorinated 9,9[prime or minute]-spirobifluorene derivatives as host materials for
18 / 29

ACCEPTED MANUSCRIPT
highly efficient blue organic light-emitting devices. J Mater Chem C 2013; 1:
2183-92.
[16] Shao S, Ding J, Wang L, Jing X, Wang F. White Electroluminescence from All-
Phosphorescent Single Polymers on a Fluorinated Poly(arylene ether phosphine
oxide) Backbone Simultaneously Grafted with Blue and Yellow Phosphors. J Am
Chem Soc 2012; 134: 20290-3.
[17] Liang A, Dong S, Zhu X, Huang F, Cao Y. White light-emitting diodes based on
an all-phosphorescent supramolecular polymer. Polym Chem 2015; 6: 6202-7.
[18] Liang A-H, Zhang K, Zhang J, Huang F, Zhu X-H, Cao Y. Supramolecular
Phosphorescent Polymer Iridium Complexes for High-Efficiency Organic Light-
Emitting Diodes. Chem Mater 2013; 25: 1013-9.
[19] Yang X, Zhou G, Wong W-Y. Functionalization of phosphorescent emitters and
their host materials by main-group elements for phosphorescent organic light-
emitting devices. Chem Soc Rev 2015; 44: 8484-575.
[20] Ying L, Ho C-L, Wu H, Cao Y, Wong W-Y. White Polymer Light-Emitting
Devices for Solid-State Lighting: Materials, Devices, and Recent Progress. Adv
Mater 2014; 26: 2459-73.
[21] Luo J, Xie Z, Lam JWY, Cheng L, Chen H, Qiu C, Kwok HS, Zhan X, Liu Y,
Zhu D, Tang BZ. Aggregation-induced emission of 1-methyl-1,2,3,4,5-
pentaphenylsilole. Chem Commun 2001; 1740-1.
[22] Tang BZ, Zhan X, Yu G, Sze Lee PP, Liu Y, Zhu D. Efficient blue emission
from siloles. J Mater Chem 2001; 11: 2974-8.
[23] Dong Y, Lam JWY, Qin A, Liu J, Li Z, Tang BZ, Sun J, Kwok HS. Aggregation-
induced emissions of tetraphenylethene derivatives and their utilities as chemical
19 / 29

ACCEPTED MANUSCRIPT
vapor sensors and in organic light-emitting diodes. Appl Phys Lett 2007; 91:
011111.
[24] Jiang H-J, Zhang J-L, Zhang Q-W, Ye S-H. Synthesis, characterization and
explosive detection of photoluminescent compounds with intramolecular charge-
transfer characteristic. Synth Met 2015; 201: 30-42.
[25] Jiang T, Qu Y, Li B, Gao Y, Hua J. Tetraphenylethene end-capped
[1,2,5]thiadiazolo[3,4-c]pyridine with aggregation-induced emission and large
two-photon absorption cross-sections. RSC Adv 2015; 5: 1500-6.
[26] Mei J, Leung NLC, Kwok RTK, Lam JWY, Tang BZ. Aggregation-Induced
Emission: Together We Shine, United We Soar! Chem Rev 2015; 115: 11718-940.
[27] Jiang Y, Wang Y, Hua J, Tang J, Li B, Qian S, Tian H. Multibranched
triarylamine end-capped triazines with aggregation-induced emission and large
two-photon absorption cross-sections. Chem Commun 2010; 46: 4689-91.
[28] Wang B, Wang Y, Hua J, Jiang Y, Huang J, Qian S, Tian H. Starburst
Triarylamine Donor–Acceptor–Donor Quadrupolar Derivatives Based on Cyano-
Substituted Diphenylaminestyrylbenzene: Tunable Aggregation-Induced Emission
Colors and Large Two-Photon Absorption Cross Sections. Chem Eur J 2011; 17:
2647-55.
[29] Yang R, Tian R, Yan J, Zhang Y, Yang J, Hou Q, Yang W, Zhang C, Cao Y.
Deep-Red Electroluminescent Polymers:ꢀ Synthesis and Characterization of New
Low-Band-Gap Conjugated Copolymers for Light-Emitting Diodes and
Photovoltaic Devices. Macromolecules 2005; 38: 244-53.
[30] Narayanan S, Raghunathan SP, Poulose AC, Mathew S, Sreekumar K, Sudha
Kartha C, Joseph R. Third-order nonlinear optical properties of 3,4-
20 / 29

ACCEPTED MANUSCRIPT
ethylenedioxythiophene copolymers with chalcogenadiazole acceptors. New J
Chem 2015; 39: 2795-806.
[31] Zhang B, Xu J, Hu L, Chen G, Yang W. Absorption-enhanced polymer solar
cells
based
on
broad
band-gap
poly(triphenylamine-alt-
benzo[c][1,2,5]selenadiazole) derivative. Materials Letters 2015; 160: 9-13.
[32] Xin Y, Wen G-A, Zeng W-J, Zhao L, Zhu X-R, Fan Q-L, Feng J-C, Wang L-H,
Wei, Peng B, Cao Y, WeiHuang W. Hyperbranched Oxadiazole-Containing
Polyfluorenes:ꢀ Toward Stable Blue Light PLEDs. Macromolecules 2005; 38:
6755-8.
[33] Hu R, Maldonado JL, Rodriguez M, Deng C, Jim CKW, Lam JWY, Yuen MMF,
Ramos-Ortiz G, Tang BZ. Luminogenic materials constructed from
tetraphenylethene building blocks: Synthesis, aggregation-induced emission, two-
photon absorption, light refraction, and explosive detection. J Mater Chem 2012;
22: 232-40.
[34] Yuan WZ, Gong Y, Chen S, Shen XY, Lam JWY, Lu P, Lu Y, Wang Z, Hu R,
Xie N, Kwok HS, Zhang Y, Sun JZ, Tang BZ. Efficient Solid Emitters with
Aggregation-Induced
Emission
and
Intramolecular
Charge
Transfer
Characteristics: Molecular Design, Synthesis, Photophysical Behaviors, and OLED
Application. Chem Mater 2012; 24: 1518-28.
[35] Becke AD. Density functional thermochemistry. III. The role of exact
exchange. J Chem Phys 1993; 98: 5648-52.
[36] Lee C, Yang W, Parr RG. Development of the Colle-Salvetti correlation-energy
formula into a functional of the electron density. Phys Rev B 1988; 37: 785-9.
[37] Frisch MJ, Trucks GW, Schlegel HB, Scuseria GE, Robb MA, Cheeseman JR,
Scalmani G, Barone V, Mennucci B, Petersson GA, Nakatsuji H, Caricato ML, X.;
21 / 29

ACCEPTED MANUSCRIPT
, Hratchian HP, Izmaylov AF, Bloino J, Zheng G, Sonnenberg JL, Hada M, Ehara
M, Toyota K, Fukuda R, Hasegawa J, Ishida M, Nakajima T, Honda Y, Kitao O,
Nakai H, Vreven T, Montgomery J, J. A.; , Peralta JE, Ogliaro F, Bearpark M,
Heyd JJ, Brothers E, Kudin KN, Staroverov VN, Kobayashi R, Normand J,
Raghavachari K, Rendell A, Burant JC, Iyengar SS, Tomasi J, Cossi M, Rega N,
Millam NJ, Klene M, Knox JE, Cross JB, Bakken V, Adamo C, Jaramillo J,
Gomperts R, Stratmann RE, Yazyev O, Austin AJ, Cammi R, Pomelli C, Ochterski
JW, Martin RL, Morokuma K, Zakrzewski VG, Voth GA, Salvador P, Dannenberg
JJ, Dapprich S, Daniels AD, Farkas Ö, Foresman JB, Ortiz JV, Cioslowski J, Fox
DJ, Gaussian, Inc., Wallingford CT, 2009.
[38] Lee T-W, Kwon Y, Park J-J, Pu L, Hayakawa T, Kakimoto M-a. Novel
Hyperbranched Phthalocyanine as a Hole Injection Nanolayer in Organic Light-
Emitting Diodes. Macromol Rapid Commun 2007; 28: 1657-62.
[39] He Q, Huang H, Sun Q, Lin H, Yang J, Bai F. A novel hyperbranched conjugated
polymer for light emitting devices. Polym Advan Technol 2004; 15: 43-7.
[40] Kim GW, Yang DR, Kim YC, Yang HI, Fan JG, Lee C-H, Chai KY, Kwon JH.
Di(biphenyl)silane and carbazole based bipolar host materials for highly efficient
blue phosphorescent OLEDs. Dyes Pigm 2017; 136: 8-16.
[41] Lv X, Wang B, Tan J, Huang Z, Zhang Q, Xiang S, Liu W, Zhuang S, Wang L.
Constructing diazacarbazole-bicarbazole bipolar hybrids by optimizing the linker
group for high efficiency, low roll off electrophosphorescent devices. Dyes Pigm
2017; 136: 54-62.
[42] Zhang F, Guan Y, Wang S, Li S, Zhang F, Feng Y, Chen S, Cao G, Zhai B.
Efficient yellow-green organic light-emitting diodes based on sublimable cationic
iridium complexes. Dyes Pigm 2016; 130: 1-8.
22 / 29

ACCEPTED MANUSCRIPT
[43] Li W, Xu T, Chen G, Zhang H, Gao X, Zhou X, Huang H, Fan H, Cai M, Zhang
X, Yang L, Zhu W, Wei B. Highly thermally-stable 4,4′-bis(4″-
triphenylsilylphenyl)-1,1′- binaphthalene as the ultraviolet amplified spontaneous
emitter, efficient host and deep-blue emitting material. Dyes Pigm 2016; 130: 266-
72.
23 / 29

ACCEPTED MANUSCRIPT
Table 1. Photophysical, electrochemical and thermal data of TPE-Se-TPE, TPA-Se-
TPE and TPA-Se-TPA
ФPL
(%)
Td
(°C)
λabs [a] λPL[a]
(nm) (nm)
Eox[b] Ered HOMO LUMO Eg
Compound
(V)
(V)
(eV)
(eV)
(eV)
TPE-Se-TPE 330, 433 552 14.2 0.45
TPA-Se-TPE 329, 461 615 36.5 0.09
TPA-Se-TPA 323, 475 624 32.4 0.13
2.48 399
2.32 406
2.24 460
−2.03 −5.25
−2.19 −4.93
−2.15 −4.89
−2.77
−2.61
−2.65
[a] Measured in neat film at room temperature. [b] Measured in a solution of Bu4NPF6 (0.1
M) in acetonitrile at a scan rate of 50 mV/s at room temperature.
Table 2. The EL performances of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA
Von [a]V [b] J [b] EQE [b] Lmax
LEmax
Device
CIE (x, y)
(V) (V) (mA cm−2) (%) (cd m− 2)(cd A−1)
TPE-Se-TPE 4.6 10.7
TPA-Se-TPE 3.2 8.6
TPA-Se-TPA 3.5 4.7
101
33.9
1.97
0.09
3.4
385
5855
2289
0.19 (0.477, 0.508)
2.91 (0.633, 0.365)
1.84 (0.653, 0.344)
2.6
[a] The turn-on voltage at which luminescence reach 1 cd m-2. [b] Device data at maximum LE.
24 / 29

ACCEPTED MANUSCRIPT
Figure captions
Scheme 1. Synthetic routes to TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA.
Figure 1. UV-vis absorption (a) and PL (b) spectra of TPE-Se-TPE, TPA-Se-TPE and
TPA-Se-TPA
Figure 2. The energies and corresponding electron density distribution of HOMO and
LUMO orbitals of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA
Figure 3. TGA curves of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA under nitrogen
atmosphere
Figure 4. (a) PL spectra of TPA-Se-TPE in THF/water mixtures with different water
fractions; (b) Changes of relative PL intensity of TPE-Se-TPE, TPA-Se-TPE and TPA-
Se-TPA in THF/water mixtures with different water fraction.
Figure 5. EL spectra of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-TPA.
Figure 6. The brightness-voltage (L–V) characteristics (a) and luminous efficiency–
current density (LE–J) characteristics (b) of TPE-Se-TPE, TPA-Se-TPE and TPA-Se-
TPA.
25 / 29

ACCEPTED MANUSCRIPT
Scheme 1
Se
N N
S
S
N
N
NaBH4
H2N NH2
Br Br
N
N
SeO2
Br2
Br
Br
Br
Br
HBr
CH3CH2OH
CH3CH2OH
1
2
3
OH
O
O
n-BuLi
THF
PTSA
O B
O
+
O
B
toluene
O
Br
n-BuLi
Br
Br
4
5
6
Se
N
N
Pd(PPh3)4
6
+ 3
TPE-Se-TPE
Pd(PPh3)4
Se
N
Se
N
N
N
6
Pd(PPh3)4
O
B
+
N
N
Br
3
N
O
7
8
TPA-Se-TPE
Se
N
N
Pd(PPh3)4
7
+ 3
N
N
TPA-Se-TPA
26 / 29

ACCEPTED MANUSCRIPT
Figure 1
(a)
1.0
0.8
0.6
0.4
0.2
0.0
TPE-Se-TPE
TPA-Se-TPE
TPA-Se-TPA
300
400
500
600
Wavelength (nm)
(b)
1.0
0.8
0.6
0.4
0.2
0.0
TPE-Se-TPE
TPA-Se-TPE
TPA-Se-TPA
500
600
700
Wavelength (nm)
Figure 2
27 / 29

ACCEPTED MANUSCRIPT
Figure 3
100
80
TPE-Se-TPE
TPA-Se-TPE
TPA-Se-TPA
60
40
0
200
400
600
800
o
Temperature ( C)
Figure 4
f
w(vol%)
(a)
TPA-Se-TPE
1000
800
600
400
200
0
10
20
30
40
50
60
70
80
90
0
500
550
600
650
700
750
Wavelength (nm)
1.5
1.2
0.9
0.6
0.3
(b)
TPE-Se-TPE
TPA-Se-TPE
TPA-Se-TPA
0.0
0
20
40
60
80
Water fraction (vol%)
28 / 29