Polymorph-Dependent Green, Yellow, and Red Emissions of Organic Crystals for Laser Applications

Article abstract of DOI:10.1002/asia.201701207

Color tuning of organic solid-state luminescent materials remains difficult and time-consuming through conventional chemical synthesis. Herein, we reported highly efficient polymorph-dependent green (P1), yellow (P2), and red (P3) emissions of organic crystals made by the same molecular building blocks of 4-(2-{4-[2-(4-diphenylamino-phenyl)-vinyl]-phenyl}-vinyl)-benzonitrile (DOPVB). Single-crystal X-ray diffraction (XRD) and spectroscopic data reveal that all three polymorphs follow the herringbone packing motif in H-type aggregations. On the one hand, from P1, P2 to P3, the reduced pitch translation along π stacks increases the intermolecular interactions between adjacent molecules, therefore leading to gradually red-shifted emissions from 540, 570 to 614 nm. On the other hand, the edge-to-face arrangement and large roll translations avoid strong π–π overlap, making P1, P2 and P3 highly emissive with record-high solid-state fluorescence quantum yields of 0.60, 0.98, and 0.68, respectively. Furthermore, the optically allowed 0–1 transitions of herringbone H-aggregates of P1, P2 and P3 naturally provide a four-level scheme, enabling green and yellow amplified spontaneous emissions (ASE) with very low thresholds.

Full text of DOI:10.1002/asia.201701207

CHEMISTRY
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Accepted Article
Title: Polymorph-dependent green, yellow and red emissions of
organic crystals for laser application
Authors: Hongbing Fu, Zhenzhen Xu, Zhiwei Zhang, Xue Jin, and Qing
Liao
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COMMUNICATION
Polymorph-dependent green, yellow and red emissions of
organic crystals for laser application**
[
a]
[a]
[a,b]
[a]
[a,b]
Zhenzhen Xu* , Zhiwei Zhang , Xue Jin , Qing Liao and Hongbing Fu*
Abstract: Color tuning of organic solid-state luminescent materials
remain difficult and time-consuming through conventional chemical
synthesis. Herein we reported highly efficient polymorph-dependent
green (P1), yellow (P2), and red (P3) emissions of organic crystals
made by the same molecular building blocks of 4-(2-{4-[2-(4-
Diphenylamino-phenyl)-vinyl]-phenyl}-vinyl)-benzonitrile (DOPVB).
Single-crystal and spectroscopy data reveal that all three
polymorphs follow the herringbone packing motif in H-type
aggregations. On the one hand, from P1, P2 to P3, the reduced pitch
translation along -stacks increases the intermolecular interactions
between adjacent molecules, therefore leading to gradually red-
shifted emissions from 540, 570 to 614 nm. On the other hand, the
edge-to-face arrangement and large roll translations avoid strong -
overlap, making P1, P2 and P3 highly emissive with record-high
solid-state fluorescence quantum yields of 0.60, 0.98, and 0.68,
respectively. Furthermore, the optically allowed 0-1 transitions of
herringbone H-aggregates of P1, P2 and P3 naturally provide a four-
level scheme, enabling green and yellow amplified spontaneous
emissions (ASE) with very low thresholds.
Highly efficient organic solid-state luminescent materials
(
OSSLMs) are of current interest in many applications, including
[
1]
[2]
luminescent sensors, bio-labeling and imaging agents, and
organic light-emitting diodes (OLEDs).
[
3]
The -conjugation
Figure
1
(A) Synthesis of DOPVB. (i) NaH, THF, RT, 8h; (ii) 4-
2 3 3
Acetylbenzonitrile, Pd(OAc) , P(o-tolyl) , NBu , DMF, 80℃ , 24h. (B) The
structures, molecular conformations and intermolecular packing
modes are three key factors that influence the optoelectronic
photographs of the crystals in glass sample bottle under the ambient light. (C)
Photographs of P1，P2 and P3 under UV light illumination (330–380 nm) of
mercury lamp in optical microscope. The scale bar is 300 µm.
[
4]
properties of OSSLMs. To date, much effort has been made to
rational design and chemical synthesis of organic chromophores
with extended -skeletons and therefore tunable emission
[
5]
wavelengths. Recently, polymorphisms of OSSLMs made by
the same molecular units are raising particular interest, because
of their significantly different optoelectronic properties stemming
from different molecular conformations and different solid-state
type (ca. 5 kJ/mol), ensuring that organic molecules aggregate
in
a
specific form (polymorphisms) and generate
micro/nanostructures with desirable functions remains a great
challenge.
[
6]
packing modes. As compared with the difficult and time-
consuming chemical synthesis, polymorphs with tunable
emissions not only provide a convenient way to tailor the
emission behavior of OSSLMs, but also provide an excellent
platform to disclose the relationship between the molecular
Optically pumped organic solid-state laser have been widely
[
8]
demonstrated, whereas electrically injected organic solid-state
laser remains a grand challenge. We recently reported organic
microcrystal lasers from both 1D nanowire Fabry-Perot and 2D
[
9]
microplate Whispering-Gallery-Mode (WGM) microresonators.
[
7]
packing mode and solid-state optical properties However,
Bao and co-workers demonstrated that filed-effect transistors
made by organic microcrystals exhibited superior carrier
because of weak intermolecular interactions of van der Waals
[
10]
mobilities than those made by poly-crystalline thin-films.
Therefore, organic microcrystals offer great opportunities to
combine high optical-gain and high carrier mobility properties
together on the way to achieve electrically injected organic solid-
state lasers. However, most of organic semiconductors, which
are highly emissive in the diluted solution, display reduced or
completely quenched emission in the solid-states, attributed to
the formation of detrimental species such as excimers and
[
a]
Dr. Z. Z. Xu, Z. W. Zhang, Dr. X. Jin, Prof. Q. L, Prof. H. B. Fu
Beijing Key Laboratory for Optical Materials and Photonic Devices
Department of Chemistry, Capital Normal University
Beijing 100048, People's Republic of China
E-mail: xuzhenzhen@cnu.edu.cn, hbfu@cnu.edu.cn
Dr. X. Jin, Prof. H. B. Fu
Tianjin Key Laboratory of Molecular Optoelectronic Sciences
Department of Chemistry, School of Sciences, Tianjin University
Collaborative Innovation Center of Chemical Science and
Engineering
[
b]
[
11]
exciplexes through intermolecular interactions.
This is
particular true for those organic semiconductors exhibiting high
carrier mobilities, such as p-type pentacene, rubrene and n-type
perylene diimides. To overcome this issue, various strategies
have been developed to adjust the intermolecular interactions.
Tianjin 300072, People's Republic of China
E-mail: hongbing.fu@tju.edu.cn
Supporting information for this article is given via a link at the end of
the document.
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COMMUNICATION
Figure 2 (A) Normalized excitation and emission spectra of P1(green line), P2(yellow line) and P3(red line) placed on a quartz plate. (B) Energy level diagram for
the optical transitions of DOPVB H-aggregates. Green energy levels correspond to nodeless excitons accessed by photon absorption, which then vibrationally
relax to the lowest energy |10> node excitons. Because of optical rules, the |10> ↔ |00> transitions are forbidden. However, the 0−n (n ≥ 1) sideband emissions,
i.e., |10>→|0n>, are allowed.
For example, Tang and other groups have reported aggregation
induced enhanced solid state emission (AIEE), based on
tetraphenylethylene skeleton through the restriction of
and weaker PL from the bodies, which were typical features of
an active optical waveguide, indicating the high quality of
crystals.
[
12]
intramolecular rotation in the solid-state. However, it is still
imperative and challenging to develop OSSLMs with tunable
wavelengths, excellent amplified spontaneous emission (ASE)
properties, and high carrier mobilities together.
Figure 2A depicts the emission and excitation spectra of
crystals P1, P2 and P3 placed on a glass substrate. For
comparison, the steady-state absorption and florescence
spectra of the DOPVB in toluene solution were shown in Figure
S2. Table 1 summarizes the related photo-physical parameters.
The maximum absorption peak of the monomers is at 441 nm
In this paper, we report controlled preparation of three kinds of
polymorphs of DOPVB microcrystals, which exhibit highly
efficient green (P1), yellow (P2) and red (P3) emissions,
respectively. All three polymorphs follow the herringbone
packing motif, in which H-aggregation is advocated. We found
that the main parameter that determines the emission maxima of
-
1
-1
with a molar extinction coefficient of ε = 49600 M ·cm , while its
emission spectrum exhibits vibrionic progression bands at 486
and 511 nm with a florescence quantum yield of Ф=0.81.
Compared with the absorption of the monomer, the excitation
spectra of these polymorphs exhibit a strongly blue-shifted
maximum around 367 nm, with additional A1 bands around 493
nm for P1, 501 nm for P2 and 533 nm for P3. The blue-shifts of
excitation maximum of these crystals than the absorption
maximum of monomers suggest that the DOPVB molecules
form H-aggregates in these crystals. The PL spectra of these
crystals are dominated by the 0−1 transition. P1 exhibits a
maximum 0-1 emission at 540 nm together with a weak shoulder
at around 565 nm. The CIE (Commission Internationale de
L’Eclairage) coordinate in Figure S3 calculated from the
spectrum is (0.38, 0.60), which is in the region of bright-green.
P2 shows yellow emission (CIE=0.52, 0.47), which exhibits
broad and structureless fluorescence peak with the maximum at
570 nm. Meanwhile, P3 shows near normal red emission
(CIE=0.63, 0.35) with the maximum emission red-shifted to 614
nm. The red-shift of the emission from P1 to P3 is consistent
[
13]
is the pitch translation along -stacks, which reduces from P1,
P2 to P3, leading to the increased intermolecular interactions
between adjacent molecules and therefore red-shifted emissions
from 535, 570 to 614 nm, respectively. Moreover, the edge-to-
[13]
face herringbone arrangements with large roll translations
minimize the - overlap between adjacent molecules, leading
record-high fluorescence quantum yields, 0.60, 0.98, and 0.68
for P1, P2 and P3, respectively. The optimized energy level of
highly emissive H-aggregates and the suitable shapes for a
waveguide structure lead to wavelength-tunable ASE with
2
2
thresholds as low as 9.5 µJ/cm for P1 and 1.94 µJ/cm for P2.
DOPVB was synthesized using a slightly modified version of
[
14]
the procedure reported in the literature (Figure 1A). Three
kinds of polymorph crystals with high quality and homogeneity
were obtained in high throughput under different growth
conditions (Figure 1B-C, Figure S1). The color of these crystals
differs from yellow-green (P1), orange-yellow (P2) to red (P3)
shown in Figure 1B. P1 was a green-emitting hexagon block
crystal with a size 2 mm × 1.5 mm prepared by the solvent
diffusion method at the liquid–liquid interface between n-hexane
and the tetrahydrofuran. Yellow-emitting rhombic block crystal
P2 with a size 1.5 mm × 1 mm and red-emitting slab-like crystal
P3 with a size 3 mm × 1 mm were prepared by slowly
Table 1．Photo-physical parameters of DOPVB monomers in toluene solution
and polymorphs P1, P2 and P3.
Sample
λ
em
Φ
F
τ
FL
k
r
k
nr
-1
-
1
[
nm]
[%]
81
60
98
68
[ns]
1.84
4.89
5.82
6.42
[ns ]
[ns ]
0.103
0.081
0.003
0.049
Solution
P1
487
540
570
614
0.44
0.123
0.169
0.104
2 2
evaporating of the saturated methylbenzene and CH Cl
P2
solutions at room temperature, respectively. Under the
illumination of mercury lamp, P1, P2 and P3 show the strong
fluorescence, with bright photoluminescence (PL) at the edges
P3
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with the calculation results in Figure S4. The value of difference
in the emission maxima between P1 and P3 is as large as 74
nm, which is among the relatively large value ever reported.
The fluorophores with π-conjugated skeleton are intrinsically
prone to cause severe concentration quenching in the H-
aggregated state as a result of the strong π-π interaction.
Especially for red emitters, it is a formidable challenge to obtain
radiative decay rates (knr) are calculated and shown in Table 1.
The fact that k
monomers is the fingerprint of H-aggregation model.
Moreover, for all crystals, the respective k is clearly larger than
nr, which is consistent the high quantum yields of these three
different crystals.
r
of the crystals are slower than that of the
[
15]
r
k
Considering that the different photo-physical properties
originate from one molecule, the molecular conformations and
packing modes are crucial for understanding the different
[
5c]
PL quantum yields exceeding 0.3 in the pure solid state.
Therefore, it is noteworthy that the high solid state florescence
quantum yields were measured to be 0.60 for green-emissive P1, emissive color with high Ф. All the crystals P1, P2 and P3 belong
0
.98 for yellow-emissive P2 and 0.68 for the red-emissive P3.
To further clarify the nature of the excited states, time-
to the triclinic space group P-1 with Z = 4 (Table S1). In all
crystals, there are two different conformations of DOPVB
molecules, respectively (named as Ⅰ and Ⅱ in Figure 3A,
details in Figure S6). In conformer Ⅰ, the diphenylamine (DPA)
group is nonplanar with the bis(styryl)benzene framework, while
it is
resolved fluorescence measurements were performed in Figure
S5. The average fluorescence lifetimes τ were estimated to be
1
.84 ns for monomers, 3.29 ns for P1, 5.82 ns for P2 and 6.42
ns for P3, respectively (Table 1). According to the equation k
/τ and knr= 1/τ - k , the radiative decay rates (k ) and the non-
r
=
Φ
F
r
r
Figure 3. (A-C) Crystal structures: top view and side view of the molecule (A), molecular packing of 16 molecules as view approximately as view approximately
down the π-stacking axis (B) and molecular packing of 16 molecules view down the long molecular axes(C) of crystal P1 (left), P2 (middle) and P3 (right).
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Table 2．Pitch and roll angles, slip distances and edge-to- face angles for P1,
P2 and P3.
S7). Moreover, the stacks packed in an edge-to-face mode. We
defined a parameter, namely, edge-to-face angle (EtF) as the
dihedral angle between each central benzene ring of the
adjacent molecule in adjacent stacks. And, the EtF angles of 53°,
87° and 60° are obtained for P1, P2 and P3. This edge-to-face
arrangement and large roll translations in herringbone motif are
beneficial for preventing excimer formation and suppressing the
concentration quenching of fluorescence, thereby keeping the
strong fluorescence of the solid samples. The largest dihedral
angle (86.73°) of the P2 effectively avoids π-π interactions
between the molecules of adjacent stacks, leading to the highest
Ф (0.98) compared with P1 (0.60) and P3 (0.68).
Stack Ⅰ
Stack Ⅱ
EtF
P
d
P
R
d
R
P
d
P
R
d
R
(deg)
(
deg)
(Å)
(deg)
67.8
49.2
53.4
(Å)
6.25
3.51
3.59
(deg)
(Å)
(deg)
69.9
44.5
59.0
(Å)
P1
P2
P3
66.5
19.9
13.7
5.85
1.10
0.65
67.4
23.1
16.3
5.70
1.29
0.76
6.50
3.28
4.32
53
87
60
more coplanar in conformer Ⅱ. The bis(styryl)benzene
framework is slightly distorted, with the dihedral angles between
terminal benzene rings and the central benzene ring in the range
of 2.91~39.44°. Considering the different molecular conformation
from P1 to P3 might attribute to their differences in photo-
physical properties, the Frontier Molecular Orbital (FMO) and the
UV-Vis spectra of these six molecules with different
conformations in crystals were calculated by time dependent
density functional theory(TD-DFT) using B3LYP/6-31G** within
the Gaussian 09 suite, which were shown in Table S2. The
variations of energy band gap induced by the different
conformation are about 0.02 - 0.04 eV. Considering band edge
of excitation spectra is red-shifted by 40 nm form 493 nm for P1
to 533 nm for P3, the molecular conformational alteration from
P1 to P3 is not the main reason for the their differences in
excitation and emission spectra and the packing mode plays a
dominant role in the photo-physical properties of the crystals.
As shown in the Figure 3B-C, the P1, P2 and P3 all show the
similar molecular packing. The molecules with same
conformation are forced into a π-stack, named as stack I and
stack II, respectively, in which, the adjacent molecules are
antiparallel with the DPA group and cyano group on the opposite
sides. Moreover, the adjacent stacks “roll” in the opposite
direction, producing a herringbone structure. Figure 3B shows a
view of the packing of DOPVB molecules as seen approximately
down the π-stacking axis. The molecules are tilted about their
short axis with a tilting angle of 50° for P1, 54° for P2 and 66° for
P3. The bigger tilting angle means higher degree of overlap,
resulting the stronger intermolecular interactions between
molecules in adjacent stacks, which help to explain the red-
shifted emission from P1 to P3.
The edge-to-face packing structures with P1-P3 suggest a
loosely molecular packing. In fact, the average volume occupied
3
by a single DOPVB molecule in the crystal is 643.07 Å for P1,
3
3
666.75 Å for P2 and 631.73 Å for P3, which is much larger
than its molecular size (Table S1). The loosely molecular
packing permits the intramolecular motion of these molecules.
However, the crystal packing is stabilized by multiple interatomic
short contacts and C-H…π interactions, which were shown in
Figure S8. These weak intermolecular interactions will fix the
molecular to inhibit the motion of these DOPVB molecules,
consistent with the smaller knr for the crystal P1 to P3 than
DOPVB in solution (Table 1).
As reported, the highly emissive H-aggregated organic
semiconductors can be superior gain materials for laser
applications, in which the optically allowed 0-1 transitions
[
9a, 9d]
naturally provide a four-level scheme.
Considering the good
waveguide property, the ASE properties of crystals P1, P2 and
P3 were studied. The ASE characteristics were successfully
[13]
The measured pitch and roll angle and the slip distances of
these π-stacks in P1，P2 and P3 are collected in Table 2. On
the one hand, the pitch angles (P) of these π-stack become
smaller from 66.5°, 67.4° for P1 to 13.7°,16.3° for P3 with the
reduced slip distances along the long molecular axis (d
p
) from
5.85 Å , 5.70 Å for P1 to 0.65 Å, 0.76 Å for P3. The reduced
pitch translation along the π-stacks which should lead to the
stronger intermolecular interactions between adjacent molecules,
accounts for the red-shift of the emission from P1 to P3. On the
other hand, all the stacks have large roll angles (R),
R
corresponding to large side slip distances (d ) about 3.3 ~ 6.5 Å.
Figure 4. PL spectra as a function of the pump laser energy and dependence
of the peak intensity (red line) and FWHM of emission spectra (black line) of
crystal P1 (A) and P2 (B) under the different pump energy.
When viewed normal to the molecular plane, the adjacent
molecules slide completely from one another, leaving little
spatial overlap of the π-systems on adjacent molecules (Figure
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Chemistry - An Asian Journal
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COMMUNICATION
observed in the P1 and P2 crystals, when optically pumped with
a 400 nm femtosecond pulse laser by using our homemade PL
setup in Scheme S1. Figure 4A and 4B show the PL spectra of
P1 and P2 crystals under different pump density (P) at room
temperature. When the single crystals were excited at 400 nm,
development of a sharp emission band at 540 nm for P1 and at
Cheng, H. Zhang, Y. Liu, Y. Wang, Angew. Chem. Int. Ed. 2015, 54,
13068-13072.
[
4]
a) B. Xu, J. He, Y. Mu, Q. Zhu, S. Wu, Y. Wang, Y. Zhang, C. Jin, C. Lo,
Z. Chi, A. Lien, S. Liu, J. Xu, Chem. Sci. 2015, 6, 3236-3241; b) X. Gu,
J. Yao, G. Zhang, Y. Yan, C. Zhang, Q. Peng, Q. Liao, Y. Wu, Z. Xu, Y.
Zhao, H. Fu, D. Zhang, Adv. Funct. Mater. 2012, 22, 4862-4872; c) D.
Yan, D. G. Evans, Mater.Horiz. 2014, 1, 46-57.
5
70 nm for P2 were clearly observed on increasing the pumping
[5]
a) M. Shimizu, T. Hiyama, Chemistry-an Asian Journal 2010, 5, 1516-
1531; b) F. Würthner, T. E. Kaiser, C. R. Saha-Möller, Angew. Chem.
Int. Ed. 2011, 50, 3376-3410; c) M. Shimizu, R. Kaki, Y. Takeda, T.
Hiyama, N. Nagai, H. Yamagishi, H. Furutani, Angew. Chem. Int. Ed.
energy. Simultaneously, the PL spectra become sharp peaks
with the FWHMs from 66 nm to 10 nm for green-emissive P1
and from 137 nm to 10 nm for the yellow-emissive P2. The
nonlinear characteristics of the pumping energy-dependent PL
intensity furthermore verify the ASE phenomenon. And the
thresholds of the ASE are as low as ~9.5 μJ·pulse for P1 and
~
the ASE thresholds for organic single crystals. However, the
ASE phenomenon has not observed around 614 nm for P3 upon
increasing the pump laser energy. Further investigations are
underway.
2012, 51, 4095-4099; d) B. Wang, Y. Wang, J. Hua, Y. Jiang, J. Huang,
S. Qian, H. Tian, Chem. Eur. J 2011, 17, 2647-2655; e) G. Li, Y. Wu, J.
Gao, C. Wang, J. Li, H. Zhang, Y. Zhao, Y. Zhao, Q. Zhang, J. Am.
Chem. Soc. 2012, 134, 20298-20301.
-
1
-
1
1.94μJ·pulse for P2, which are among the lowest values of
[
6]
a) K. Wang, H. Zhang, S. Chen, G. Yang, J. Zhang, W. Tian, Z. Su, Y.
Wang, Adv. Mater. 2014, 26, 6168-6173; b) J. W. Chung, Y. You, H. S.
Huh, B.-K. An, S.-J. Yoon, S. H. Kim, S. W. Lee, S. Y. Park, J. Am.
Chem. Soc. 2009, 131, 8163-8172; c) Z. He, L. Zhang, J. Mei, T. Zhang,
J. W. Y. Lam, Z. Shuai, Y. Q. Dong, B. Z. Tang, Chem. Mater. 2015, 27,
6601-6607; d) P. Galer, R. C. Korošec, M. Vidmar, B. Šket, J. Am.
In summary, highly emissive organic crystals with different
colors from green through yellow to red were obtained based on
one new compound DOPVB. The large difference in emission
might originate from the different pitch translation along the π-
stacks in the herringbone packing structure. The reduced pitch
translations from P1, P2 to P3 increase the intermolecular
interactions between the adjacent molecules in the π-stacks,
accounts for the red-shifted emissions from 540, 570 to 614 nm.
The ultrahigh quantum yield could be attributed to the large roll
translations and the edge-to-face packing mode which minimize
the π−π interactions. What's more, the optically allowed 0-1
transitions of H-aggregates in herringbone motif naturally
Chem. Soc. 2014, 136, 7383-7394..
[
[
7]
8]
Z. Zhang, Y. Zhang, D. Yao, H. Bi, I. Javed, Y. Fan, H. Zhang, Y. Wang,
Cryst. Growth Des. 2009, 9, 5069-5076.
a) I. Samuel, G. Turnbull, Chem. Rev 2007, 107, 1272-1295; b) H.-H.
Fang, J. Yang, J. Feng, T. Yamao, S. Hotta, H.-B. Sun, Laser
Photonics Rev. 2015, 9, 128-128.
[9]
a) Z. Xu, Q. Liao, Q. Shi, H. Zhang, J. Yao, H. Fu, Adv. Mater. 2012, 24,
OP216-OP220; b) X. Wang, Q. Liao, Q. Kong, Y. Zhang, Z. Xu, X. Lu,
H. Fu, Angew. Chem. Int. Ed. 2014, 53, 5863-5867; c) X. Wang, Q.
Liao, X. Lu, H. Li, Z. Xu, H. Fu, Sci. Rep. 2014, 4, 7011; d) Z. Xu, Q.
Liao, X. Wang, H. Fu, Adv. Optical Mater. 2014, 2, 1160-1166.
[
[
10] J. Mei, Y. Diao, A. L. Appleton, L. Fang, Z. Bao, J. Am. Chem. Soc.
013, 135, 6724-6746..
2
provide
a four-level scheme. The optimized energy level
11] R. H. Friend, R. W. Gymer, A. B. Holmes, J. H. Burroughes, R. N.
Marks, C. Taliani, D. D. C. Bradley, D. A. Dos Santos, J. L. Bredas, M.
Logdlund, W. R. Salaneck, Nature 1999, 397, 121-128.
together with the high-quality crystals with the high quantum
yield, enable ASE characters with very low threshold of 9.5
-
1
[
[
[
12] Y. N. Hong, J. W. Y. Lam, B. Z. Tang, Chem. Soc. Rev. 2011, 40,
5361-5388.
μJ·pulse for green-emissive single crystals P1 and 1.94
-
1
μJ·pulse for yellow-emissive single crystals P2. Although
crystals P3 were not found obvious ASE property, the efficient
red-emissive fluorescence with the ultrahigh quantum yield of
13] M. D. Curtis, J. Cao, J. W. Kampf, J. Am. Chem. Soc. 2004, 126, 4318-
4328.
14] E. Cariati, C. Dragonetti, E. Lucenti, F. Nisic, S. Righetto, D. Roberto, E.
0.68 is very important for the optoelectronic devices, such as
Tordinab, Chem. Commun. 2014, 50, 1608-1610.
OLEDs and fluorescent sensors.
[15] F. C. Spano, Accounts. Chem. Res. 2010, 43, 429-439.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (Grant Nos. 21190034, 91222203,
2
1273251, 21221002, 91333111, 21503139, and 21673144),
the National Natural Science Foundation of China (Grant Nos.
162011), project of State Key Laboratory on Integrated
2
Optoelectronics of Jilin University (IOSKL2014KF16), project of
Beijing Municipal Education Commission (KM20161002800 8),
project of Construction of Innovative Teams and Teacher Career
Development for Universities and Colleges Under Beijing
Municipality (IDHT20140512), the National Basic Research
Program of China (973) and 2013CB933500, and the Chinese
Academy of Sciences.
Keywords: polymorph •organic crystals• amplified spontaneous
emission • high photoluminescence quantum yeild• photophysics
[
[
1]
2]
S. Thomas III, G. Joly, T. Swager, Chem. Rev. 2007, 107, 1339-1386.
Z. Xu, Q. Liao, Y. Wu, W. Ren, W. Li, L. Liu, S. Wang, Z. Gu, H. Zhang,
H. Fu, J. Mater. Chem. 2012, 22, 17737.
[
3]
a) A. C. Grimsdale, K. Leok Chan, R. E. Martin, P. G. Jokisz, A. B.
Holmes, Chem. Rev. 2009, 109, 897-1091; b) S. Wang, X. Yan, Z.
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Chemistry - An Asian Journal
10.1002/asia.201701207
COMMUNICATION
COMMUNICATION
Highly luminescent single crystals with
difference in the emission colour from
green through yellow to red were
obtained based on one new
compound DOPVB. Excitingly, the
Zhenzhen Xu*, Zhiwei Zhang, Xue Jin,
Qing Liao and Hongbing Fu*
Page No. – Page No.
red-emissive
ultrahigh fluorescence quantum yield
Ф) of 0.68. The other two crystalline
forms are green-emissive with Ф of
crystals
possess
Polymorph-dependent green, yellow
and red emissions of organic crystals
of laser application
(
0.60 and the yellow-emissive with Ф of
0.98, which displayed excellent ASE
characteristics with extremely low
threshold.
This article is protected by copyright. All rights reserved.