Centimeter-sized inorganic lead halide perovskite CsPbBr3 crystals grown by an improved solution method

Article abstract of DOI:10.1021/acs.cgd.7b01086

As a member of the lead-halide perovskite family, inorganic perovskite CsPbBr₃ exhibits excellent optical and electrical properties with higher stability to the environment. However, former efforts to obtain large-size CsPbBr₃ single crystals with satisfactory quality using low temperature solution methods reached limited results. In this work, we have studied the growth of CsPbBr₃ crystals using the antisolvent vapor-assisted crystallization (AVC) method. By adjusting the mole ratio of PbBr2 and CsBr, the phase diagram of the final products is acquired. Five regions are identified, including the Cs₄PbBr₆ single phase region, Cs₄PbBr₆ and CsPbBr₃ two phases region, CsPbBr₃ single phase region, CsPbBr₃ and PbBr2· 2[(CH₃)₂SO] metastable two phases region, and CsPbBr₃ and PbBr2·2[(CH₃)₂SO] two phases region. Three methods are adopted to improve the size and crystalline quality of CsPbBr₃. The growth rate is effectively tailored by diluting the antisolvent MeOH solution using DMSO to reduce the MeOH vapor pressure. Centimeter-size bright CsPbBr₃ crystals have been obtained. The room temperature bandgap of CsPbBr₃ is estimated at ～2.29 eV by the transmission spectra. The photoluminescence spectra show two strong emission peaks, located at 530 and 555 nm, respectively, which are related to the free and bond excitons. The resistivity is as large as 2.1 × 109 Ω· cm. Hall effect measurements demonstrate the CsPbBr₃ is p-type conductivity with a hole carrier concentration of 4.55 × 107 cm^-3 and the mobility of 143 cm² V^-1 s^-1. The resulting Au/CsPbBr₃/Au device exhibits strong photoresponse to optical light, with an on-off ratio of two orders under a light emitting diode (～1 mW/cm2) with a wavelength of 365-420 nm. Our research would shed more light on the growth and the photoresponse properties of CsPbBr₃ crystals.

Full text of DOI:10.1021/acs.cgd.7b01086

Article
pubs.acs.org/crystal
Cite This: Cryst. Growth Des. XXXX, XXX, XXX-XXX
Centimeter-Sized Inorganic Lead Halide Perovskite CsPbBr3 Crystals
Grown by an Improved Solution Method
Hongjian Zhang, Xin Liu, Jiangpeng Dong, Hui Yu, Ce Zhou, Binbin Zhang,* Yadong Xu,*
and Wanqi Jie
State Key Laboratory of Solidification Processing & Key Laboratory of Radiation Detection Materials and Devices & School of
Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China
ABSTRACT: As a member of the lead-halide perovskite family, inorganic perovskite CsPbBr3
exhibits excellent optical and electrical properties with higher stability to the environment.
However, former efforts to obtain large-size CsPbBr3 single crystals with satisfactory quality
using low temperature solution methods reached limited results. In this work, we have studied
the growth of CsPbBr3 crystals using the antisolvent vapor-assisted crystallization (AVC)
method. By adjusting the mole ratio of PbBr2 and CsBr, the phase diagram of the final products
is acquired. Five regions are identified, including the Cs4PbBr6 single phase region, Cs4PbBr6
and CsPbBr3 two phases region, CsPbBr3 single phase region, CsPbBr3 and PbBr2·
2[(CH3)2SO] metastable two phases region, and CsPbBr3 and PbBr2·2[(CH3)2SO] two
phases region. Three methods are adopted to improve the size and crystalline quality of
CsPbBr3. The growth rate is effectively tailored by diluting the antisolvent MeOH solution
using DMSO to reduce the MeOH vapor pressure. Centimeter-size bright CsPbBr3 crystals
have been obtained. The room temperature bandgap of CsPbBr3 is estimated at ∼2.29 eV by
the transmission spectra. The photoluminescence spectra show two strong emission peaks,
located at 530 and 555 nm, respectively, which are related to the free and bond excitons. The resistivity is as large as 2.1 × 109 Ω·
cm. Hall effect measurements demonstrate the CsPbBr3 is p-type conductivity with a hole carrier concentration of 4.55 × 107
cm−3 and the mobility of 143 cm2 V−1 s−1. The resulting Au/CsPbBr3/Au device exhibits strong photoresponse to optical light,
with an on−off ratio of two orders under a light emitting diode (∼1 mW/cm2) with a wavelength of 365−420 nm. Our research
would shed more light on the growth and the photoresponse properties of CsPbBr3 crystals.
antisolvent vapor-assisted crystallization (AVC),10 respectively.
1. INTRODUCTION
Dirin9 reported CsPbBr3 crystals grown from DMSO using the
Compared with the hybrid perovskites, all inorganic lead halide
ITC method and the related solutions. Millimeter-sized
perovskites have excellent photoelectrical properties, as well as
CsPbBr3 crystals were obtained. However, when it was used
higher chemical stability to the environment. As a member of
for γ-ray detection, only a broad photopeak was observed
inorganic perovskites, CsPbBr3 (CPB) has direct optical band
illuminated by a 241Am source at 220 K, but no peak appeared
gap, large optical absorption (∼2.3 eV),1,2 narrow emission line
at room temperature. The mobility lifetime product (μτ) is ∼2
width, high luminescence, and high quantum yield, which make
× 10−4 cm2 V−1, which is slightly lower than that of Bridgman-
it suitable for application in the fabrication of strong
grown CsPbBr3 crystals.1 The resistivity is about 2 GΩ·cm,
which is also smaller than that grown by the Bridgman method
(343 GΩ·cm).1 Another AVC solution method is suggested by
Rakita et al. and other groups.10−12 Cha et al.,11 Ding et al.,12
and Miao et al.13 reported the photodetector properties of
solution-growth CsPbBr3 crystals. However, only millimeter
sized crystals with relative low resistivity (less than 1 GΩ·cm)
and poor mobility ∼13.6 cm2 V−1 s−1 were obtained due to the
defects and impurities.13
luminescent colloidal quantum dots (QDs),3−5 air-stable
perovskite solar cells,6 highly sensitive visible light detectors,7
highly polarization-selective three-photon absorption,8 and
high-energy detectors.1,9
To understand the potential optoelectrical properties of
CsPbBr3, high quality of CsPbBr3 bulk crystals are desirable.
Stoumpos1 reported CsPbBr3 bulk crystals grown by the
Bridgman method at high temperature (above 600 °C) used for
X- and γ-rays detection. However, the obtained CsPbBr3 single
Except for the low resistivities,9−13 mobilities,13 and
lifetimes,9 due to the defects and impurities, a more essential
problem is to control the phase in the Cs−Pb−Br system when
growing CsPbBr3 crystals from solution. From the phase
crystals suffered from phase transition (Pm3m above 410 K,
̅
P4/mbm from 410 to 375 K, Pbnm below 375 K) after the
crystallization, resulting in a high density of grown-in defects.1
Compared with melt growth, the solution growth can avoid the
phase transition in the crystal and should be a favorable method
for preparing CsPbBr3 perovskite crystals. Two low temper-
ature solution growth methods have been reported recently,
including inverse temperature crystallization (ITC)9 and
Received: August 5, 2017
Revised: September 22, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.cgd.7b01086
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Crystal Growth & Design
Article
Figure 1. (a) The schematic diagram of CsPbBr3 crystals grown by the AVC method. (b) The pictures of the final crystals obtained from the
precursor solution with n changing from 0.25 to 4, where n is the starting mole ratio of PbBr2 and CsBr. (c) The obtained yellow, orange, and white
crystals are determined as Cs4PbBr6, CsPbBr3, and PbBr2·2[(CH3)2SO] using the XRD patterns refinements.
diagram,14 it is seen that there are three phases including
2.2. Growth of CsPbBr3 Single Crystals. CsPbBr3 single crystals
CsPbBr3, CsPb2Br5, and Cs4PbBr6, respectively. Rakita et al.10
were grown by the AVC method. As shown in Figure 1a, about 20 mL
and Saidaminov et al.2 found that it is difficult to control the
of clear precursors were put in the inner container, and 30 mL of
antisolvent (MeOH or diluted MeOH) was added in the outer
exact composition of the obtained crystals from the solution
container. MeOH solution was volatilized from the outer container to
due to the complex factors, such as the ratio of the starting
the inner one, forming a saffron yellow precipitation of CsPbBr3. It is
materials, the kinds of solution and antislovent, and even the
temperature. CsPbBr3 and Cs4PbBr6 tend to generate
noted that the mole ratios of PbBr2 and CsBr from 1 to 1.5 is required
to form pure CsPbBr3 crystals. This growing process lasted 3−14 days,
simultaneously if the ratios of the starting materials PbBr2
and CsBr are not adjusted carefully.2,10 Only several millimeters
size CsPbBr3 crystals are obtained from the solution
method.2,9,10
So it is still a challenge to obtain large size CsPbBr3 crystals
with high quality by optimizing the growth conditions of the
solution method. In this work, we study the low temperature
solution growth of CsPbBr3 crystal by the AVC method. The
phase diagram of Cs−Pb−Br system is determined according to
the ratio of PbBr2 and CsBr. To control the growth rate, we
propose a new method by using dilute antisolvent to reduce the
vapor pressure of MeOH.
depending on the composition of the mixed antisolvent. The final
crystals were washed with dimethylformamide (DMF) solution at
room temperature. By using the optimum conditions that the mole
ratio of PbBr2 and CsBr in the precursor is 1.5 and the mixed
antisolvent composition is 50% MeOH and 50% DMSO, we obtained
the largest CsPbBr3 crystals with a size of 42 × 5 × 3 mm3.
2.3. Characterizations and Measurements. The X-ray
diffraction (XRD) patterns of both powders and single crystal were
collected using D/Max2500PC with Cu Kα1 in the range of 10−90°
(2θ) under a tube voltage of 40 kV and 40 mA. The UV−vis spectra of
CsPbBr3 crystals were carried out on a UV-2550 spectrometer with an
integrating sphere over the spectral range of 400−800 nm. A FLS-920
fluorescence spectroscopy was used to collect photoluminescence
(PL) spectra, with the excitation wavelength of 405 nm. Current−
voltage (I−V) and current−time (I−t) were measured by electrical
properties measurement system (Agilent 4155C). A light emitting
diode (LED) (∼1 mW/cm2) was employed as the illumination light to
perform the time-dependent photoresponse with the wavelength of
365−420 nm.
2. EXPERIMENTAL SECTION
2.1. Preparation of Precursors. CsBr (≥99.5%) and PbBr2
(≥99.5%) were used as the starting materials, and methylalcohol
(≥99.5%) and dimethyl sulfoxide (DMSO, ≥99.5%) as the solvents
for the growth of CsPbBr3 crystals. Nine millimoles of PbBr2 and 6
mmol of CsBr were dissolved by 15 mL of DMSO with continuous
stirring for 1 h at room temperature. After that, the solution was
filtered using 30 μm-sized filter paper to remove the green-yellow
precipitate. Then, the clear solution was titrated with MeOH until the
orange precipitate no longer dissolved. Finally, the titrated mixed
solution was filtered again to obtain the precursor for crystal growth. A
series of variable precursors were obtained by changing the mole ratios
of PbBr2 and CsBr from 0.25 to 4.
3. RESULTS AND DISCUSSION
3.1. Phase Diagram in Cs−Pb−Br System. The starting
mole ratio of PbBr2 and CsBr is very important for the final
crystallization from DMSO solution. Dirin9 and Saidaminov2
found that if the ratio of PbBr2 and CsBr is equal to 1:1, the
resulting CsPbBr3 is always mixed with Cs4PbBr6. Pure
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1 − n
4n − 1
CsPbBr3 phase can be achieved when the ratio was increased to
2:1. In our work, the variable mole ratios of PbBr2 and CsBr
(n:1) have been studied for the crystallization process, where n
changes from 0.25 to 4. When the antisolvent MeOH
volatilized into the precursors, complex crystallizations can be
observed at the bottom of the container. Figure 1b shows the
pictures of the evolution of the resulting crystallizations with a
different mole ratio of PbBr2 and CsBr (n:1). When n varies
from 0.25 to 1, the colors of the obtained crystallization change
from bright yellow to orange gradually. Further increasing n
from 1 to 1.5, the color turns orange, and the grain sizes
become large. When n changes from 1.5 to 4, another white
stick-like crystallization was generated and mixed with the
orange crystals. To determine the phases of crystallizations with
different colors, the XRD patterns were measured, as illustrated
in Figure 1c. After the refinements of XRD patterns, the yellow,
orange, and white crystallizations were determined as Cs4PbBr6,
CsPbBr3, and PbBr2·2[(CH3)2SO], respectively. It should be
noted that the white stick-like crystals are not PbBr2, but the
organic crystal PbBr2·2[(CH3)2SO].15 Its space group is Pmmn,
and the lattice parameters are a = 11.108 Å, b = 12.400 Å, and c
= 4.548 Å, respectively.
nPbBr2 + CsBr →
Cs4PbBr6 +
CsPbBr3
3
3
⎛
⎜
⎞
⎟
1
4
< n < 1
⎝
⎠
PbBr2 + CsBr → CsPbBr3 (1 ≤ n < 1.3)
nPbBr2 + CsBr + 2(n − 1)(CH3)2SO
→ CsPbBr3 + (n − 1)PbBr2·2[(CH3)2SO]
(1.3 ≤ n ≤ 1.5) (metastable) (n > 1.5)
According to eq 1, when n is below 1/4, only green Cs4PbBr6
crystals precipitate from the solution. When n is between 1/4
and 1, green Cs4PbBr6 and orange CsPbBr3 crystals can grow
up simultaneously. When n is between 1 and 1.3, only the
orange CsPbBr3 crystals grow from the solution. When n is
between 1.3 and 1.5, orange CsPbBr3 crystals can grow up at
first. After a slight vibration, the extra PbBr2 in the solution can
form the complex PbBr2·2[(CH3)2SO] with DMSO gradually.
This is a metastable region. When n is above 1.5, both orange
CsPbBr3 and white PbBr2·2[(CH3)2SO] crystals are generated.
3.2. Control of the Crystal Growth. The crystallization
process takes place once the precursor solubility is reduced by
the interdiffusion of the antisolvent. Figure 3 shows the
To identify the variable crystallizations at different values of
n, the starting components dependent phase diagram is plotted
in Figure 2a. It is suggested that when the value of n is between
Figure 2. (a) The phase diagram of the final products in Cs−Pb−Br
systems grown from DMSO solution using MeOH as an antisolvent. It
is noted that the metastable region (n = 1.3−1.5) is observed with the
components of CsPbBr3 and PbBr2·2[(CH3)2SO]. (b) After a slight
vibration of the solution, an increasing amount of the white PbBr2·
2[(CH3)2SO] crystals is observed over time.
Figure 3. Relationship of the obtained mass (or moles) of CsPbBr3
crystals and the moles of MeOH volatilized into the precursor
solution. Accordingly, the pictures of CsPbBr3 crystals obtained in the
solution are shown below this curve.
1.3 and 1.5, the metastable region is observed. As shown in
Figure 2b, the state of the solutions changes over time (0 s to
30 s) after a slight disturbance. At the beginning, only orange
CsPbBr3 crystals are generated at the bottom of the container.
After a slight vibration, the white PbBr2·2[(CH3)2SO] crystals
are formed quickly. Thirty seconds later, the orange CsPbBr3
crystals are almost covered by the white PbBr2·2[(CH3)2SO]
crystals.
According to the results of the crystallization experiments,
five crystallization regions are obtained as a function of the
value of n. We propose the following four reactions to explain
the crystallization process.
relationship between the mass (or molar quantity) of the
resulting CsPbBr3 crystals and the antisolvent MeOH
volatilized in the precursor solution. The mole ratio of CsPbBr3
and MeOH in the solution is about 7 × 10−3. Accordingly,
CsPbBr3 crystals were generated from the precursor solution, as
shown in the bottom of Figure 3. When 625 mmol of MeOH
volatilized into the solution, the mass of CsPbBr3 crystals can
achieve at as large as 1.8 g. Therefore, the maximum volume
could be 0.40 cm3 considering the density of CsPbBr3 is about
4.55 g/cm3. This indicates that the antisolvent MeOH can
produce large CsPbBr3 crystals by reducing the solubility of the
precursor solution.
In order to obtain large crystals with high quality, it is
necessary to control the growth rate and the amount of
nucleation. For this solution growth, three aspects should be
taken into account, including (1) the diffusion of the
⎛
⎞
⎟
1
4
1
4
1
4
⎜
PbBr2 + CsBr → Cs4PbBr6 n ≤
⎝
⎠
(1)
C
DOI: 10.1021/acs.cgd.7b01086
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Crystal Growth & Design
Article
Figure 4. (a) The vapor pressures of the composited antisolvent MeOH and DMSO with changing XMeOH, where XMeOH is the mole ratio of MeOH.
The value of XMeOH of the green dash line is the concentration of MeOH in antisolvent solution of outer container, while the green dash line
represents the concentrate of MeOH in the precursor solution in the inner container. When MeOH in the antisolvent solution is volatized into the
precursor solution, the concentration of MeOH in two containers change along the pink line. Finally, they both have the same value of XMeOH. (b)
The orange CsPbBr3 crystals are obtained at the variable value of XMeOH in the antisolvent solutions from 100% to 50%. With decreasing value of
XMeOH, the maximum sizes of crystals are increased. (c) The XRD patterns of the CsPbBr3 crystals are shown with a set of peaks identified as (0l0)
faces.
Figure 5. (a) The transmittance and PL spectra of CsPbBr3 crystals. (b) The energy gap is fitted as 2.29 eV by the Tauc plot curve. (c) The PL
spectra are measured at the variable incident powers from 0.55 mW to 5.06 mW. The inset is the relationship between incident powers and PL
intensities. The fitting values of γ for two peaks are 1.44 and 1.48, respectively. (d) The color picture presents the changes of PL intensities at
variable powers and wavelengths.
antisolvent from the outside container to the inner one; (2) the
concentration of Pb2+ and Br− in the precursor solution; (3)
the vapor pressure of the antisolvent MeOH in the outside
container.
possibly because MeOH diffuses still too fast from the outside
container into the inner one by controlling the area of pores,
and thus this method is not effective to improve the size and
quality of CsPbBr3 crystals.
First, the sizes of the pores connecting inside and outside
containers were adjusted for controlling the diffusion of
antisolvent MeOH. When the areas of the pores were adjusted
from several square centimeters to hundreds square microns,
the crystallization rate did not result in a significant difference.
Within 1−2 days, the amounts of crystal were not increased
anymore. Because of the fast growth rate of CsPbBr3 crystals,
the maximum size of obtained crystals is usually only several
millimeters, which is similar to the previous reports. This is
Second, increasing the amount of PbBr2 could influence the
crystallization rate. At the same growth time, the relative larger
CsPbBr3 crystals are generated by increasing the amount of
PbBr2, as shown in Figure 1b. Therefore, more Pb2+ and Br−
ions in the DMSO solution can decrease the CsPbBr3 crystals
dissolving speed. But when the PbBr2 is too large amount, the
white stick-like crystals PbBr2·2[(CH3)2SO] will dissolve out
from the DMSO solution. Further growth of CsPbBr3 crystals,
however, is prevented because of the appearance of these white
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Article
crystals. So the value of n is suggested at the metastable region
(n = 1.3−1.5), which ensures the growth of a relatively large
amount of PbBr2 simultaneously, and avoids the formation of
the white stick-like PbBr2·2[(CH3)2SO] crystals.
strongly bound excitons.16,17 Because the free exciton is more
close to the bandgap, we think the 530 nm peak is attributed to
free exciton emission and the 550 nm peak is contributed by
the bound-exciton emission. The color picture in Figure 5d also
presents the changes of PL intensities at variable powers and
wavelengths. The positions of two peaks are constant with the
changing of incident powers. And the full width at half-
maximum (fwhm) of two peaks are around 17 nm, which are
broadened slightly with the increased incident powers.
The photoresponse properties of CsPbBr3 grown by the
improved AVC method have also been evaluated. Au/CsPbBr3/
Au structure device was fabricated by thermally evaporating Au
contacts with the thickness of 60 nm on the opposite face of the
wafers, as shown in Figure 6a. I−V curves are measured in dark
Third, reducing the vapor pressure of the antisolvent MeOH
can decrease the CsPbBr3 crystal growth rate effectively.
According to the ideal solution partial pressure law, the vapor
pressure of the antisolvent MeOH is controlled by mixed
MeOH and DMSO. At room temperature, the vapor pressure
of DMSO is about 49 Pa, which is three orders lower than
MeOH (1−2 × 105 Pa). So the partial pressure of DMSO can
be ignored for the calculation of the vapor pressure of MeOH
in the mixed solution. As shown in Figure 4a, the vapor
pressure of MeOH is reduced by decreasing the mole amount
of MeOH. The precursor solution is consisted of DMSO and
30−40% MeOH, where MeOH is used to prepare the saturated
solution. In order to ensure that MeOH in the outside
container can enter into the precursor, the concentration of
MeOH in the antisolvent solution should not be below 30−
40%. By this diluted antisolvent method, the growth time can
last from 2 days to 2 weeks. MeOH over DMSO with the mole
ratios of 100%, 80%, 70%, 60%, and 50% are applied when n =
1.5 for the crystal growth. As shown in Figure 4b, the sizes of
orange CsPbBr3 crystals are increased from millimeters to
centimeters. The maximum size of CsPbBr3 crystals is about 42
× 5 × 3 mm3 at 50% MeOH in the antisolvent. The
transparency of CsPbBr3 crystals obtained from diluted MeOH
antisolvents is better than the ones from pure MeOH. XRD
patterns of CsPbBr3 single crystal from the diluted antisolvent
exhibits a set of (0 l 0) diffraction surface, as shown in Figure
4c. The inset in Figure 4c is the crystal structure of CsPbBr3,
which is related to the space group Pnma. The lattice
parameters are a = 8.37 Å, b = 8.425 Å, c = 12.011 Å, α = β
= γ = 90°.
3.3. Optical and Photoresponse Properties. The optical
properties of CsPbBr3 grown by the improved AVC method
have been studied at room temperature. Figure 5a shows the
transmission spectra and the PL spectra from 400 to 800 nm.
From the transmission spectrum, a sharp rise in the curve is
observed at around 550 nm, which is in agreement with the
previous reports.1,2,11 And a relative higher average trans-
mittance of ∼57% is obtained from 550 to 800 nm. By fitting
the Tauc plot, the energy band gap (Eg) was calculated to be
∼2.29 eV, demonstrated in Figure 5b, which is higher than 2.25
eV1 that grown from the melt method, 2.16 eV12 and 2.21 eV2
that grown by the solution method. It is noted that two peaks at
around 530 and 555 nm, respectively, are observed with strong
intensity in the room temperature PL spectrum under an
incident power of 5.06 mW. Only one broad peak at around
550 nm in the PL spectra has been reported from the solution-
grown CsPbBr3 crystals,2,9−11,15 while Stoumpos et al. observed
two peaks at 46 K PL from the melt-grown CsPbBr3 crystals.1
In order to interpret the two peaks, the incident power
dependent PL spectra were measured from 510 to 600 nm.
Figure 5c shows the power dependent PL spectra from 5.06
mW to 0.5 mW. The positions of two peaks are constant with
the value of 530 and 555 nm, respectively, under different
incident powers. Analysis of the PL peak intensity (I) versus
incident beam intensity (F) displays a power law dependence (I
α Fγ) for both the 530 nm and the 555 nm peaks. The inset
picture of Figure 5c shows the values of the exponential
coefficient γ are 1.44 and 1.48, respectively. The values between
1 < γ < 2, generally, is indicative of PL emission through
Figure 6. (a) The schematic diagram of the electrode structure with
Au electrodes and the measurement of the photoresponse. (b) The I−
V curves of CsPbBr3 single crystal measured from −1 V to 1 V at dark.
(c) The photoresponse of CsPbBr3 are shown at variable wavelengths
of 365−420 nm with the incident power about 1 mW/cm2.
with bias from −1 to 1 V, Figure 6b. The dark current of
CsPbBr3 crystal is about 0.1 nA at 1 V. And the bulk resistivity
of CsPbBr3 crystal at room temperature is about 2.1 × 109 Ω·
cm, which is close to that of CdTe crystals.18 This ensures the
CsPbBr3 as a potential semiconductor for room temperature X-
or γ-rays detection with lower electronic noise. Figure 6c shows
the photoresponse illuminated by an LED light in the
wavelengths range of 365−420 nm and with the intensity of
∼1 mW·cm−2. The ON/OFF ratio is as high as about 102 at 1
V bias, which is several times higher than the data reported by
Ding et al.5 Hall effect measurements are carried out on the as-
grown CsPbBr3 crystals. CsPbBr3 exhibits p-type conductivity
with a hole carrier concentration of 4.55 × 107 cm−3 and the
mobility of 143 cm2 V−1 s−1, as shown in Table 1. Except for
the melt-grown CsPbBr3, the CsPbBr3 crystals grown in our lab
have a higher quality than the reported crystals obtained by the
solution method (including AVC and ITC).
4. CONCLUSIONS
Centimeter-size CsPbBr3 crystals were grown by a modified
AVC solution method at low temperature. By controlling the
mole ratio of PbBr2 and CsBr, the phase diagram with five
regions was obtained, including Cs4PbBr6, CsPbBr3, PbBr2·
2[(CH3)2SO] single phase regions and the mixed phases
regions. To improve the size and crystalline quality of CsPbBr3
crystals, three methods were employed to tailor the growth
speed. The most effective method is to dilute the MeOH
solution with DMSO. The vapor pressure of the antisolvent
MeOH is controlled by changing the diluted ratios. At the ratio
of 50%, a CsPbBr3 crystal with a size of 42 × 5 × 3 mm3 was
E
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Article
a
Table 1. Electronic Parameters of CsPbBr3 Single Crystals Grown by Different Methods
crystal growth method
AVC
size (mm3)
resistivity (Ω·cm)
mobility (cm2 V−1 s−1
)
carrier concentration (cm−3
)
ref
42 × 5 × 3
2 × 1 × 1
0.67 × 2.0 × 0.51
millimeter-sized
3 × 2 × 1
2.1 × 109
4.0 × 106
6.2 × 107
∼1 × 106
1 × 108
143
4.55 × 107
1.13 × 1010
this work
AVC
AVC
AVC
ITC
13.6
13
11
12
2
52 (electron)
11 (hole)
1.1 × 109 (electron)
1.4 × 108 (hole)
ITC
7 × 3 × 2
centimeter-sized
2 × 109
3.43 × 1011
9
1
melt-grown crystallization
1000
a
Where AVC and ITC is antisolvent vapor-assisted crystallization method and inverse temperature crystallization method, respectively.
(9) Dirin, D. N.; Cherniukh, I.; Yakunin, S.; Shynkarenko, Y.;
Kovalenko, M. V. Chem. Mater. 2016, 28, 8470−8474.
(10) Rakita, Y.; Kedem, N.; Gupta, S.; Sadhanala, A.; Kalchenko, V.;
Bohm, M. L.; Kulbak, M.; Friend, R. H.; Cahen, D.; Hodes, G. Cryst.
Growth Des. 2016, 16, 5717−5725.
obtained. The bandgap of CsPbBr3 is 2.29 eV. Two strong
emission peaks at 530 and 555 nm in the PL spectra were
observed, which are attributed to the strong bond excitons. The
obtained p-type CsPbBr3 crystals exhibited high resistivity of
∼2.1 × 109 Ω·cm. The CsPbBr3 device shows a promising
photoresponse to the optical light, with an on−off ratio of
∼100 under an LED light at the wavelength of 365−420 nm
(∼1 mW·cm−2).
(11) Cha, J. H.; Han, J. H.; Yin, W.; Park, C.; Park, Y.; Ahn, T. K.;
Cho, J. H.; Jung, D. Y. J. Phys. Chem. Lett. 2017, 8, 565−570.
(12) Ding, J. X.; Du, S. J.; Zuo, Z. Y.; Zhao, Y.; Cui, H. Z.; Zhan, X. Y.
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(13) Miao, X.; Qiu, T.; Zhang, S.; Ma, H.; Hu, Y.; Bai, F.; Wu, Z. J.
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AUTHOR INFORMATION
Corresponding Authors
*Tel: +86-29-88460445; e-mail: zbb@nwpu.edu.cn (B.Z.).
*E-mail: xyd220@nwpu.edu.cn (Y.X.).
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ORCID
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Binbin Zhang: 0000-0002-1874-1881
Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
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This work was supported by the National Natural Science
Foundations of China (Nos. U1631116 and 51202197). Project
was also supported by the National Key Research and
Development Program of China (2016YFE0115200), the
Natural Science Basic Research Plan in Shaanxi Province of
China (2016KJXX-09), and the Fundamental Research Funds
for the Central Universities (3102017zy057).
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DOI: 10.1021/acs.cgd.7b01086
Cryst. Growth Des. XXXX, XXX, XXX−XXX