Solvothermal Synthesis of Ultrathin Cesium Lead Halide Perovskite Nanoplatelets with Tunable Lateral Sizes and Their Reversible Transformation into Cs4PbBr6 Nanocrystals

Article abstract of DOI:10.1021/acs.chemmater.8b00612

The versatility of perovskite crystal structure has become the great advantage of lead halide perovskite nanocrystals (NCs) during their functional applications. Here we report an effective solvothermal method for the controllable synthesis of CsPbBr

Full text of DOI:10.1021/acs.chemmater.8b00612

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Article
Solvothermal Synthesis of Ultrathin Cesium Lead Halide
Perovskite Nanoplatelets with Tunable Lateral Sizes and
Their Reversible Transformation into Cs4PbBr6 Nanocrystals
Wei Zhai, Jing Lin, Qiaoling Li, Kun Zheng, Yang Huang, Yuanzhao Yao, Xin
He, Lanlan Li, Chao Yu, Chang Liu, Yi Fang, Zhenya Liu, and Chengchun Tang
Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.8b00612 • Publication Date (Web): 10 May 2018
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Chemistry of Materials
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Solvothermal Synthesis of Ultrathin Cesium Lead Halide Perovskite
Nanoplatelets with Tunable Lateral Sizes and Their Reversible
Transformation into Cs4PbBr6 Nanocrystals
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Wei Zhai†,‡, Jing Lin†,‡,*, Qiaoling Li†,‡, Kun Zheng§, Yang Huang†,‡,*, Yuanzhao Yao⊥, Xin He†,‡,
Lanlan Li†,‡, Chao Yu†,‡, Chang Liu†,‡, Yi Fang†,‡, Zhenya Liu†,‡, Chengchun Tang†,‡
† School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, P. R. China
‡ Hebei Key Laboratory of Boron Nitride Micro and Nano Materials, Hebei University of Technology, Tianjin 300130,
P. R. China
§ Institute of Microstructure and Properties of Advanced Materials, Beijing Key Lab of Microstructure and Property
of Advanced Material, Beijing University of Technology, Beijing 100124, P. R. China
⊥Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki
305-0044, Japan
ABSTRACT: The versatility of perovskite crystal structure has become the great advantage of lead halide perovskite nano-
crystals (NCs) during their functional applications. Here we report an effective solvothermal method for the controllable
synthesis of CsPbBr3 nanoplatelets (NPLs) and their transformation to Cs4PbBr6 NCs. Through solvothermal reaction of a
mixture of Cs-oleate and PbBr2 precursors, CsPbBr3 NPLs can be synthesized in mass production. The lateral sizes of CsP-
bBr3 NPLs can be precisely tuned by varying the solvothermal reaction temperatures and times, while the thickness of
NPLs keeps constantly at ~4.2 nm, which is in quantum confinement regime. The fine-tuning of lateral NPLs sizes results
in precise modulation of their photoluminescence emission. Moreover, an interesting phase transformation from cubic
CsPbBr3 NPLs to rhombohedral Cs4PbBr6 NCs, and the reversible transformation from Cs4PbBr6 NCs to CsPbBr3 NPLs can
be readily achieved by changing the solvothermal reaction sources. The present solvothermal approach is simple, conven-
ient, controllable, and can be easily extended to preparation of other perovskite NCs with different halide compositions.
INTRODUCTION
attracted increased attention. In 2015, Kovalenko group
reported the synthesis of CsPbX3 NCs by an air-free hot
injection method. The halide compositions can be easily
changed via ion-exchange transformations, resulting in
the tunable photoluminescnece (PL) emission.18 Deng
group developed a ligand-mediate reprecipitation method
for manipulating the shape of CsPbX3 NCs. Diverse
CsPbX3 NCs, including quantum dots, nanocubes, nano-
rods and nanoplatelets (NPLs), have been synthesized
and shown distinct shape-dependent PL emissions.20
Moreover, Manna group reported the interesting mono-
layer-level thickness control over CsPbBr3 NPLs to achieve
thickness-dependent PL emission.28 Very recently, the
chemical transformation of CsPbBr3 NCs to get a new
kind of lead−halide depleted perovskite derivative, i.e.
Cs4PbX6 NCs, has also attract much attention.29-31 The
Cs4PbX6 phase has been considered as a type of zero-
dimensional perovskite, showing a differently insulator
bandgap.32, 33
Lead halide perovskite nanocrystals (NCs) recently have
gained huge interest due to their outstanding optical and
electronic properties, thus have shown great potential for
applications in light-emitting diodes (LEDs),1-5 photovol-
7
taic cells,6, photodetectors,8-10 etc. Due to the intrinsic
instability and soft nature, lead halide perovskite NCs can
be synthesized in a variety of sizes, shapes, and composi-
tions,11-13 such as organic-inorganic hybrid perovskites
CH3NH3PbX3 (X=Cl, Br, I)15-17 and all-inorganic perovskites
CsPbX3 (X=Cl, Br, I)18, 19 in various morphologies (quan-
tum dots,18 nanowires,12, 21 nanoplatelets,22, 23 nanocubes,24,
etc). The versatility of perovskite crystal structure has
become the great advantage of lead halide perovskite NCs
for their functional applications.
25
Precisely control over the morphology, structure and
composition of lead halide perovskite NCs not only offers
great opportunity for accessing novel nanostructures, but
also allows for understanding the growth evolution of
NCs and establishing their structure-property link. Since
Although great efforts have been devoted to the con-
trollable synthesis of lead halide perovskite NCs, many
challenges still remain. The air-free hot injection method
has been considered as the most mature approach for
the pioneering work reported by Kovalenko group,18,
the research on controllable synthesis of all-inorganic
26, 27
CsPbX3 NCs with tailored morphology and structure has
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synthesis of CsPbX3 NCs.11, 18, 27, 34 However, the rapid reac-
Page 2 of 9
solution displays yellow color with a very high concentra-
tion (right), suggesting large-scale production of CsPbBr3
NPLs. The diluted NPLs dispersion (50 times diluted)
shows a brighter yellowish green color (left). A ~0.192 g
amount of yellow powder was successfully fabricated per
single experimental run (Figure 1e), implying that the
CsPbBr3 NPLs synthesized by the solvothermal method
are easy to achieve mass production.
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tion in very short time is not facilitate for the controllable
synthesis. With the aim of precisely control over such tiny
NCs, a relatively mild crystal growth environment is fa-
35
vorable. In this paper, we develop a facile solvothermal
method for the controllable synthesis of CsPbBr3 NPLs
and their transformation to Cs4PbBr6 NCs. The readily
effective method results in the production of uniform
CsPbBr3 NPLs in a large-scale. Owing to the sealed envi-
ronment of the solvothermal method, there is no extra
procedures for an inert atmosphere which are usually
necessary in the other methods. 18, 20 In the solvothermal
synthesis, the reaction between Cs-oleate and PbBr2 pre-
cursors can take place at relatively low temperatures and
the kinetics of the reaction can also be depressed. As a
result, we can succeed in achieving monodisperse CsPbBr3
NPLs with precisely tuned lateral sizes by simply adjust-
ing the reaction times or temperatures. In addition, we
demonstrate that the developed solvothermal method can
be extended for further structure and composition control
over the cesium lead halide NCs. An successful reversible
transformation between CsPbBr3 NPLs and Cs4PbBr6 NCs
can be achieved by simply changing the amount of Cs-
oleate or PbBr2 precursors.
After continuously dilution from the diluted CsPbBr3
dispersion (shown in left of Figure 1d) for about 50 times,
the obtained solution was used for testing of their spectral
properties. Figure 1f shows the UV-vis absorption, PL
emission and excitation spectra of the CsPbBr3 NPLs. The
characteristic absorption peak is located at ~449 nm. The
excitation spectrum exhibits an excitation peak at ~448
nm, which is in good agreement with the UV-vis absorp-
tion result. The emission spectrum consists of a narrow
emission peak centered at ~456 nm. Because of the size of
CsPbBr3 NPLs relative to its exciton Bohr diameters (∼7.0
nm), the observed blue shift of CsPbBr3 relative could be
explained by the quantum confinement effect.38 PL quan-
tum yield (QY) measurements show a high QY of ~50%
for the as-prepared CsPbBr3 NPLs, which is higher than
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bulk crystal
and CsPbBr3 nanosheets.28,
The high
PLQY could be related to a low density of trap states in
the present NPLs.39 The PL decay curve of the NPLs is
shown in Figure 1g, which can be fitted well with the tri-
exponential decay function. The estimated average PL
lifetime is of ~4.87 ns, which is comparable with those of
previously reported CsPbBr3 NPLs (~3-4.3 ns).28, 39
RESULTS AND DISCUSSION
The CsPbBr3 NPLs were prepared by a solvothermal
method using a mixture of Cs-oleate and PbBr2 precursors
at relatively low temperatures (60-180 °C). Detailed syn-
thetic conditions are shown in Supporting Information.
The proposed growth process has been illustrated in
Scheme 1. Firstly, PbBr2 was dissolved into the octade-
cene (ODE)/oleylamine (OLA)/oleic acid (OA) solution to
get a PbBr2 precursor. After dissolving of Cs2CO3 into
ODE/OA, Cs-oleate precursor was also generated. The
precursors were fully mixed together at room temperature
and then transferred into an autoclave. After solvother-
mal reaction, CsPbBr3 NPLs were obtained. All the opera-
tions were completed in ambient atmosphere.
Interestingly, the optical properties of the CsPbBr3
NPLs can be precisely controlled by simply changing the
solvothermal reaction times, as displayed in Figure 2a.
With an increase of reaction time, the emission peak
shifts from 453 nm to 465 nm, implying that our approach
can achieve more precise modulation of PL emissions of
perovskite CsPbBr3 as compared with other reported syn-
43
thetic methods.24, 27, 42 Figure 2b show the UV-vis ab-
sorption and PL emission spectra of CsPbBr3 NPLs pre-
pared at different reaction times. CsPbBr3 NPLs with tun-
able absorption peak positions ranging from 446 nm to
460 nm could be achieved by varying the reaction time
from 30 min to 24 h. We also measured the PL lifetimes of
the different CsPbBr3 samples (Figure S2). As the reaction
time increases, the lifetime of NPLs increases slightly
from 3.2 ns to 9.9 ns. There is no significant change in the
PLQY from 39% to 52% (Figure S3), indicating that pro-
longed solvothermal reaction time did not cause excessive
surface defects in the CsPbBr3 NPLs.
The perovskite phase of as-prepared sample has been
confirmed by powder X-ray diffraction (XRD) analysis. As
shown in Figure 1a, the diffraction pattern can be well
indexed into cubic CsPbBr3 (PDF card No. 54-752). No
other phases were detected, suggesting the high purity of
the product. Transmission electron microscopy (TEM)
image shown in Figure 1b indicates that the CsPbBr3
product has regular NPL morphology. The sharp edges
suggest a single crystalline nature for each NPL. The small
black spots existing in the NPLs are metallic lead nano-
particles, which can be confirmed by the HAADF-STEM
image (Figure S1). Similar lead nanoparticles have also
been observed in other previously reported CsPbBr3 NCs,
TEM images of the CsPbBr3 samples are shown in Fig-
ure 2c-f. All of the products consist of numerous regular
NPLs with good monodispersity and uniform size. With
an increase of reaction time, the shape of the NPLs gradu-
ally changes from narrow rectangle into square. The aver-
age later dimensions change from 100.7 ± 9.4 nm * 15.2 ±
5.3 nm to 44.1 ± 3.8 nm * 42.4 ± 5.9 nm (Figure 2g-j), in-
dicating that the lateral size control can be well achieved
MAPbBr3 sheets36 and CsPbBr3 nanosheets37. Through
28
characterization of high-resolution TEM (HRTEM) image
of perpendicularly oriented NPLs (Figure 1c), the thick-
ness of NPLs can be estimated to be ~4.2 nm, correspond-
ing to 7 monolayers of CsPbBr3.38 Figure 1d shows a photo
image of as-prepared product dispersed in n-hexane. The
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Scheme 1. Schematic diagram of solvothermal synthesis process.
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Figure 1. (a) XRD pattern of CsPbBr3 NPLs prepared at 100 °C for 60 min. (b) TEM image of the lying flat CsPbBr3 NPLs
prepared at 100 °C for 60 min. (c) TEM image of the perpendicularly oriented CsPbBr3 NPLs. (d) Photograph of CsPbBr3
NPLs dispersed in n-hexane with low concentration (left) and high concentration (right). (e) Photograph of the CsPbBr3
NPLs powder prepared per single experimental run. (f) Optical absorption (UV-vis, green line), PL emission (PL, black
dash line), and PL excitation (PLE, red line) spectra of the sample. (g) Time-resolved PL decay and fitting curves of the
light emission at 456 nm from CsPbBr3 NPLs.
by tuning the solvothermal reaction times (also see Fig-
ure S4).
2.83 to 2.70 eV when the thickness of CsPbBr3 NPLs in-
creases from 3 to 5 monolayers28). This value is much
larger than the average PL shift distances observed in our
samples.
It has been previously demonstrated that the CsPbBr3
NPLs with a thickness relative to the exciton Bohr of CsP-
41
bBr3 display strong thickness-dependent PL emission.28,
To validate the hypothesis that the PL shift origins from
the tunable lateral size, we further performed TEM analy-
sis on the stacks of aligned CsPbBr3 NPLs to estimate their
thickness. As shown in Figure 2k and 2l, the NPLs are
lying perpendicularly with respect to the carbon film. For
the initial sample (30 min, 100 °C), the NPLs have a thick-
ness of ~4.2 nm. Interestingly, after the reaction time was
prolonged to 24 h, the thickness of the obtained CsPbBr3
sample remains fixed at ~4.2 nm. It is also noteworthy
that, since only a single emission peak has been observed
The control of the plate thickness with various number of
monolayers enables regularly PL position shift due to the
strong quantum confinement. However, it is noteworthy
that, in our method, it is most likely that the tunable lat-
eral size is responsible for the red-shifted PL emission,
rather than the thickness variation.39 In fact, both theo-
retical study and experimental data have shown that, if
the number of CsPbBr3 monolayer increase, PL position
will shift with an average distance of more than ~10 nm 28,
38, 41, 44
(Manna group observed a distinct PL shift from
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Figure 2. (a) PL emission spectra of CsPbBr3 NPLs prepared at 100 °C for 30, 60, 200, 420 min and 24 h respectively. (b)
UV-vis absorption (solid line) and PL emission spectra (dash line) of the different CsPbBr3 NPLs. (c-f) TEM images of
CsPbBr3 NPLs prepared at various reaction times. (g-j) The corresponding statistical histograms on the lateral sizes of
CsPbBr3 NPL samples. (k) TEM image of the perpendicularly oriented CsPbBr3 NPLs prepared at 100 °C for 30 min. (l)
TEM image of the perpendicularly oriented CsPbBr3 NPLs prepared at 100 °C for 24 h.
in the spectra, all the CsPbBr3 samples should have a uni-
form size distribution. Therefore, by varying the sol-
vothermal reaction times, we were able to fine-tune the
lateral size of the NPLs while keeping their thickness
fixed in the strong quantum confinement regime, and
achieving the precise PL emission control. We also con-
duct a theoretical calculation to evaluate the red-shift PL
of the NPLs with different sizes. Preliminary results are
shown in Figure S5.
plays a vital role in the size control. The low temperature
and high pressure environment enable the reaction be-
tween Cs-oleate and PbBr2 precursors to take place at
relatively low temperatures and the kinetics of the reac-
tion can also be depressed. As a result, CsPbBr3 NPLs with
tuned lateral sizes can be obtained by adjusting the reac-
tion times. In addition, we changed the amine ligands
with different carbon chains instead of OLA. No NPLs
were obtained (Figure S6), indicating that the OLA lig-
ands play an important role on the formation of CsPbBr3
NPLs. During the solvothermal reaction, the OLA ligands
capping on the nuclei surface promote the anisotropic
NPL growth effectively. The vertical growth rate of CsP-
bBr3 nuclei has been depressed, leading to the formation
of NPLs. It is also noteworthy that, with the solvothermal
time increasing, the lateral sizes of NPLs gradually
change, while the vertical thickness still remains con-
stantly. Even after long reaction for 24 h, the average size
of the NPLs still remains in quantum confinement re-
It is noteworthy that the lateral sizes of CsPbBr3 NPLs
prepared after different solvothermal reaction times are
still relative to the quantum confinement regime, which is
quite different from CsPbBr3 nanosheets with microme-
ter-sized lateral dimension reported by Manna group.39
Therefore, the tunable lateral size control could lead to
the precisely controlled PL emission. Unlike the hot injec-
tion method which can immediately quench the reaction
by ice-water bath 1, 18, the present solvothermal synthesis
in the sealed environment still leads to quality NPLs with
precisely tunable lateral sizes. We believe that the rela-
tively low crystal growth rate in the solvothermal reaction
gime.
Therefore,
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Figure 3. (a) XRD patterns of various products obtained by changing the reaction conditions, showing the conversion
from cubic CsPbBr3 to rhombohedral Cs4PbBr6 and a reversible transformation from rhombohedral Cs4PbBr6 to cubic
CsPbBr3. (b) UV-vis absorption (solid line) and PL emission (spherical dashed line) of Cs4PbBr6 NCs (blue line) and
CsPbBr3 NPLs (green line). (inset) Photographs of two samples, showing distinc color change.
Figure 4. (a-d) TEM images of samples prepared by solvothermal reaction using increased amount of Cs-oleate
precursors (2 mL, 3.5 mL, 7.0 mL and 20 mL, respectively), showing transformation from pure CsPbBr3 NPLs (a) into pure
Cs4PbBr6 NCs (d). (e-g) TEM images of samples prepared by solvothermal reaction of the pre-synthesized Cs4PbBr6 NCs
with different amount of PbBr2 precursor (10 mL, 20 mL and 35 mL, respectively), showing revisible transformation from
Cs4PbBr6 NCs to CsPbBr3 NPLs. (h-j) The structural models of cubic CsPbBr3 and rhombohedral Cs4PbBr6. (k-n) HRTEM
images and the corresponding FFT patterns of CsPbBr3 NPLs and Cs4PbBr6 NCs, respectively.
the precise lateral size control can be achieved via chang-
ing the solvothermal reaction times. The reason for NPL
growth with dimension variations under the particular
solvothermal reactions is unkown till date and needs fur-
ther investigations.
60 °C to 180 °C. TEM images also show the well-dispersed
homogeneous NPLs have lateral size variation with the
temperature increase. The gradually increase of lateral
width and decrease of lateral length enables the red shift
of PL emission.
The solvothermal reaction temperature is also critical
in controlling the lateral size and tuning the PL properties
of CsPbBr3 samples. As shown in Figure S7-S8, the PL
emission peaks of the samples could be tuned from 450
nm to 465 nm by varying the reaction temperatures from
Moreover, the present solvothermal method can be fur-
ther extended for structure and composition control over
the cesium lead halide NCs. In fact, our method enables
the successful transformation of CsPbBr3 NPLs to
Cs4PbBr6 NCs by increasing the amount of Cs-oleate pre-
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cursor and the reversible transformation from Cs4PbBr6
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obtained (Figure 4g). Figures 4h-j show the structural
models and phase transformation between cubic CsPbBr3
and rhombohedral Cs4PbBr6.
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NCs to CsPbBr3 NPLs through adding a certain amount of
PbBr2 precursor to the pre-synthesized Cs4PbBr6 NCs. To
the best of our knowledge, our work constitute the first
report on the successful reversible structural and compo-
sition transformation between CsPbBr3 NPLs and
Cs4PbBr6 NCs.
HRTEM images clearly show the well-defined CsPbBr3
NPLs and hexagonal-shaped Cs4PbBr6 NCs (Figures 4k, l),
respectively. The measured d-spacing of 6.8 Å matches
well with the {110} plane of rhombohedral Cs4PbBr6. The
corresponding fast Fourier transform (FFT) patterns are
show in Figures 4m-n. SEM image of the synthesized
Cs4PbBr6 NCs also displays uniform and monodisperse
morphology (Figure S12). The large area monolayer of
NCs indicates the high yield production of Cs4PbBr6 NCs.
The average size of the resulting Cs4PbBr6 NCs is ~12.5
nm. In fact, Cs4PbBr6 NCs with increased diameters can be
obtained by simply prolong the solvothermal reaction
time as shown in Figure S13.
In fact, herein the solvothermal growth of CsPbBr3 NPLs
is under Pb rich reaction conditions with an excess of
PbBr2 precursor.45 By gradually increasing the amount of
Cs-oleate precursor (from 2 mL to 20 mL), the obtained
product changes from cubic CsPbBr3 phase into rhombo-
hedral Cs4PbBr6 phase, as determined by XRD analysis
shown in Figure 3a. After adding of 20 mL Cs-oleate pre-
cursor, the obtained product shows peaks at 2θ=12.6, 12,9,
20.1, 22.4, 25.6 and 30.5° corresponding to diffractions
from {012}, {110}, {113}, {300}, {024} and {223} planes of
rhombohedral Cs4PbBr6 (PDF card No 73-2478). The color
of the product changes from initial light green to milky
white (Inset of Figure 3b). Interestingly, we also find that
the Cs4PbBr6 NCs can be further transformed into CsP-
bBr3 NPLs by a post synthesis reaction with PbBr2 precur-
sor. By reacting a certain amount of PbBr2 precursor with
the presynthesized Cs4PbBr6 NCs, the product changed
into pure perovskite CsPbBr3 phase completely (Figure
3a). More detailed structure transformation has been dis-
played in Figure S9 and supporting information.
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CONCLUSIONS
In summary, a facile solvothermal method has been de-
veloped for the large-scale preparation of ultrathin CsP-
bBr3 NPLs using a mixture of Cs-oleate and PbBr2 precur-
sors. Through varying the reaction temperatures and/or
times, the lateral sizes of CsPbBr3 NPLs can be well con-
trolled while their thicknesses are still kept in the quan-
tum confinement regime. Different with the thickness-
dependent PL emission reported by other research
groups, our method enables the fine-tuning of lateral NPL
sizes, leading to more precise modulation of PL emis-
sions. Moreover, the CsPbBr3 NPLs can be converted into
hexagonal-shaped Cs4PbBr6 NCs by using increased
amount of Cs-oleate precursor during the solvothermal
reaction. Interestingly, through solvothermal reaction of
PbBr2 precursor with the pre-synthesized Cs4PbBr6 NCs,
an reversible transformation from Cs4PbBr6 NCs to CsP-
bBr3 NPLs have been achieved. The developed solvother-
mal method leads to the successful control over the size,
structure and composition of cesium lead halide NCs,
which can find widespread applications in solar cells,
light-emitting diodes, photodetectors and lasers. We also
envision that the synthetic approach can be easily extend-
ed to synthesis of other perovskite NCs with different
halide compositions.
Optical studies indicate that the transformed Cs4PbBr6
NCs exhibit different absorption and PL emission peaks
compared with initial CsPbBr3 NPLs (Figure 3b). The UV-
vis characteristic absorption peak has been shifted to ~314
nm. These absorbance feature is consistent with previous
experimental and theory studies on Cs4PbBr6 NCs,46 im-
plying its wide bandgap. We believe that Cs4PbBr6 NCs
will not exhibit PL emission in the visible range because
of the wide bandgap (Cs4PbBr6=3.95 eV).47 The observed
weak PL emission originates from minor CsPbBr3 impuri-
ties mixed in the Cs4PbBr6 product, even if apparently no
trace of CsPbBr3 phase can be found in XRD results. Since
CsPbBr3 displays a high PLQY, the green PL emission can
be detected from only a very small trace of CsPbBr3 impu-
rities in the product. Similar opinion has also been re-
ported by Akkerman et al.47 PL emissions of the interme-
diate products with mixed phases are also shown in Fig-
ure S10.
ASSOCIATED CONTENT
The structural and composition transformation be-
tween CsPbBr3 NPLs and Cs4PbBr6 NCs was further con-
firmed by TEM analysis. The NPLs gradually become ir-
regular and some NCs with hexagonal shape begin to ap-
pear (Figures 4a-c). HRTEM images of the intermediate
product are shown in Figure S11. Upon increasing the
amount of Cs-oleate precursor to 20 mL, monodisperse
Cs4PbBr6 NCs with uniform hexagonal shape can be ob-
tained (Figure 4d). Moreover, by post-solvothermal reac-
tion of the pre-synthesized Cs4PbBr6 NCs with different
amounts of PbBr2 precursor, an interesting reversible
transformation from Cs4PbBr6 NCs into CsPbBr3 NPLs
takes place (Figures 4d-g). Finally pure CsPbBr3 NPLs
with well size distribution and shape uniformity can be
Supporting Information.
Experimental details on conditions for the various syntheses,
additional data from structural analysis (HAADF-STEM,
TEM, FFT, Time-resolved PL decay, SEM, XRD, UV-vis and
PL spectra), theoretical calculation, additional data from
statistical diagrams and optical photos. This material is avail-
able free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
* E-mail: linjing@hebut.edu.cn (J. Lin)
* E-mail: huangyang@hebut.edu.cn (Y. Huang)
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(12) Wang, Y.; Sun, X.; Shivanna, R.; Yang, Y.; Chen, Z.; Guo, Y.;
Wang, G. C.; Wertz, E.; Deschler, F.; Cai, Z.; Zhou, H.; Lu, T. M.;
Shi, J. Photon Transport in One-Dimensional Incommensurately
Epitaxial CsPbX3 Arrays. Nano Lett. 2016, 16, 7974-7981.
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ACKNOWLEDGMENT
This work was supported by the National Natural Science
Foundation of China (51572068, 51772075), the Natural Sci-
ence Foundation of Hebei Province (E201620212), the Hun-
dred Talents Program of Hebei Province (E2014100011), and
the Program for Changjiang Scholars and Innovative Re-
search Team in University (PCSIRT: IRT13060).
(13) Zhang, D.; Eaton, S. W.; Yu, Y.; Dou, L.; Yang, P. Solution-
Phase Synthesis of Cesium Lead Halide Perovskite Nanowires. J.
Am. Chem. Soc. 2015, 137, 9230-9233.
(14) Liang, J.; Liu, J.; Jin, Z. All-Inorganic Halide Perovskites for
Optoelectronics: Progress and Prospects. Solar RRL 2017, 1,
1700086.
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