Air-stable CsPb1-xBixBr3 (0 ≤ x ? 1) perovskite crystals: Optoelectronic and photostriction properties

Article abstract of DOI:10.1039/c7tc00417f

The growth of single crystals allows a more accurate and reliable study of the intrinsic electrical and optical properties of halide perovskite materials. However, all-inorganic halide perovskite single crystals are difficult to prepare due to the poor solubility of the reactant precursors. In this paper, we report a series of air-stable Cs-based halide perovskite single crystals, CsPbBr₃ and CsPb_1-xBi_xBr₃ (x ? 1), prepared via a modified antisolvent vapour-assisted crystallization method. The Cs-based halide perovskites exhibited low trap density and high carrier mobility that are comparable to those of organic-inorganic hybrid halide perovskite materials. Most importantly, the Bi-doped CsPb_1-xBi_xBr₃ perovskites also indicated excellent light absorption (covering the entire visible wavelength) and photostriction (effective photostriction of about 8 × 10^-4) performances, which greatly expands the optoelectronic and optomechanical applications of these inorganic halide perovskite materials.

Full text of DOI:10.1039/c7tc00417f

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ISSN 2050-7526
PAPER
~
Nguyên T. K. Thanh, Xiaodi Su et al.
Fine-tuning of gold nanorod dimensions and plasmonic properties using
the Hofmeister effects
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Air-stable CsPb1−xBixBr3 (0 ≤ x
optoelectronic and photostriction properties
) perovskite crystals:
Received 00th January 20xx,
Accepted 00th January 20xx
Xiaoliang Miao,a Ting Qiu,a Shufang Zhang,*a He Ma, a Yanqiang Hu,a Fan Bai,a Zhuangchun Wu*b
DOI: 10.1039/x0xx00000x
www.rsc.org/
The growth of single crystals allows more accurate and reliable study the intrinsic electrical and optical properties of halide
perovskite materials. However, all-inorganic halide perovskites single crystals are difficult to prepare due to poor solubility
of the reactant precursors. In this paper, we report a series of air-stable Cs-based halide perovskite single crystals, CsPbBr3
and CsPb1−xBixBr3 (x
), prepared via a modified antisolvent vapour-assisted crystallization method. The Cs-based halide
perovskites exhibited low trap density and high carrier mobility that comparable to those of organic-inorganic hybrid
halide perovskite materials. Most importantly, the Bi-doped CsPb1−xBixBr3 perovskites also indicated excellent light
absorption (covering the entire visible wavelength) and photostriction (effective photostriction of about 8×10-4)
performances, which greatly expands the optoelectronic and opto-mechanical applications of these inorganic halide
perovskite materials.
studied in thin film solar cells and LEDs, the intrinsic electrical and
optical properties of CsPbX3 still require further study. Generally, it
is difficult to understand the ultimate potential properties of CsPbX3
1 Introduction
Organic-inorganic hybrid halide perovskite materials have been
widely studied in optoelectronic and electronic field in the past
years owing to their high absorption coefficient, excellent carrier
mobility and long carrier life time.1-6 In particularly, solar cells with
CH3NH3PbI3 (MAPbI3) and formamidinium lead iodide (FAPbI3) as
light absorbers have attracted tremendous research interest and
the efficiency of perovskite solar cells has raised explosively from
3.8% to over 22% in few years.7,8 Nevertheless, the further large-
scale applications of such perovskite solar cells are still limited by
the air-instability of these organic-inorganic hybrid perovskites.
Most recently, their counterparts air-stale all-inorganic halide
perovskite materials such as CsPbX3 (X= Cl, Br, and I) are emerging
to be efficient light-harvesting and photoluminescent materials.9-11
The Cs-based perovskites have been proved to have better
mechanical and air stability than the MA or FA-based hybrid halide
perovskites and to be favourable as optoelectronic materials.12, 13
However, the larger bandgap of CsPbX3 lead to a narrower light
absorption. Therefore, perovskite solar cells based on pure CsPbX3
as light absorber are hardly to obtain high efficiency. CsPbX3 has
been frequently incorporated with MAPbI3 or FAPbI3 as light-
harvesters to improve the stability of solar cells.14,15 On the other
hand, although the Cs-based perovskites have been intensively
in the form of polycrystalline thin films because a lot of defects such
as grain boundaries, voids, and surface defects are in the
polycrystalline films. In comparison, single crystals with very few
defects provide an excellent prototype to study the utmost of these
perovskite materials. So far, several approaches for growth of the
MA-based and FA-based perovskite single crystals have been
reported. Bakr and co-workers reported an antisolvent vapour-
assisted crystallization approach that can grow MAPbX3 (X = I or Br)
single crystals with volumes exceeding 100 mm3.18 Huang and co-
workers reported using a top-seeded solution method with a
temperature gradient and obtained a MAPbI3 single crystal with size
of 10 mm.19 Later, an inverse temperature crystallization method
was reported to grow MAPbX3 (X= Cl, Br, and I) single crystals within
several minutes.20,21 For growth of the FA-based perovskite single
crystals, Yang and co-workers using a modified inverse temperature
crystallization method and obtained a 5 mm sized FAPbI3 single
crystal.22 Liu and co-workers grew a large FAPbI3 single crystal with
20 mm in size.23 However, the growth of Cs-based perovskite single
crystal is rarely reported.24,25 This is mainly due to poor solubility of
the reactant precursors of CsPbX3 and uncontrollability of the
growth of CsPbX3 perovskite single crystals. Hence, it is always a
challenge to grow large-sized Cs-based halide perovskite single
crystals.
In this paper, we present a series of Cs-based halide perovskite
a.College of Materials Science and Engineering, Nanjing University of Science and
Technology, Nanjing 210094, China. E-mail: zhangshufang@njust.edu.cn
b.Institute of Functional Materials, Donghua University,Shanghai, 201620, China. E-
mail: zwc@dhu.edu.cn
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
CsPbBr3 and CsPb Bi Br (x
) single crystals prepared via a
1
−
x
x
3
modified antisolvent vapour-assisted crystallization method and
explore the structures and electrical and optical properties of these
single crystals. To extend light absorption of CsPbBr3, we chose Bi3+
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system (Perkin Elmer) with Mg Kα radiation (hν = 1486.6 eV).
Transmission electron micrographs were taken
with relatively strong absorption ability as the doping element.
Although the Bi3+ has a higher valence than Pb2+, the much closed
ionic radius of Bi3+ and Pb2+ provides some possibility of
substitutional doping within the crystal. The CsPbBr3 and
using FEI Tecnai G20 transmission electron microscope (TEM). The
relative dielectric constants (ε) of the single crystals were measured
by an impedance analyser. Current-voltage (I–V) measurements
CsPb1−xBixBr3 (x
) single crystals all exhibited excellent electrical
properties e.g. low trap density and high carrier mobility
comparable to those of the MA-based and FA-based perovskite
single crystals. The optical absorption measurements demonstrated
were performed by using
Photostrictive responses measurements were recorded by a Brook
Multimode atom force microscopy (AFM). During the
a Keithley 2400 Source Meter.
8
that the Bi-doped CsPb1−xBixBr3 (x
) crystals have much broader
photostriction test, the light (from either a halogen lamp or a laser
diode) was guided through an optical fibre into the built-in optical
microscope of the AFM. The light intensity at the sample location
absorption spectra than CsPbBr3 and the absorption spectra cover
the entire visible spectrum, which greatly expands the potential
applications of Cs-based inorganic hybrid perovskites in
was carefully calibrated using
a commercial energy meter
optoelectronic field. More importantly, the CsPb1−xBixBr3 (x
)
(Newport, 91,150 V). Furthermore, the beam size was adjusted as
about 0.1 cm2 on the sample location.
single crystals demonstrated excellent photostriction performances,
endowing these materials with tremendous prospects in emerging
applications, such as microactuations and microsensings.
Results and discussion
3.1 Single crystal growth and structural characterization
Experimental
The single crystals were grown using a modified antisolvent vapour-
assisted crystallization method. The CsPbBr3 and CsPb1−xBixBr3
2.1 Chemicals and reagents
Lead bromide (PbBr2, >98%), cesium bromide (CsBr, 99.9%),
bismuth bromide (BiBr3, >98%), N,N-dimethylformamide (DMF,
anhydrous, 99.8%), and toluene (99.9%) were purchased from
Sigma Aldrich. All salts and solvents were used as received without
any further purification.
(x
) seed crystals were firstly grown by a cooling solution
method, followed by placing the seed crystals in a saturated
precursor solution wrapped by vapour of the anti-solvent to obtain
larger crystals. The as-grown single crystals had an average size of 2
mm and the largest size is ∼4 mm (Fig.1a and Fig. S1). There was no
significant difference in shapes of the CsPbBr3 and CsPb1−xBixBr3
2.2 Growth of CsPbBr3 and CsPb1-xBixBr3 (x
) single crystals
(x
) single crystals, which are all in cuboid shape. Apparently,
A mixture of CsBr and PbBr2 in molar ratio of 1:1 was dissolved in
DMF to form supersaturated solution with calculated
colour of the pure CsPbBr3 and the Bi-doped CsPb1−xBixBr3 (x
)
a
crystals was very different. With the bismuth component increases,
the crystal colour changed from orange to dark red. The elemental
compositions of the as-grown single crystals are analysed by EDS
and the charts of EDS are shown in Fig S2. The stoichiometric
component of the CsPbBr3 crystal was confirmed by the EDS. The
concentration as 1.5 M. The supersaturated solution was stirred
thoroughly at 70° for further use. The crystals growth process is
schematically shown in scheme 1. To grow seed crystal of CsPbBr3,
the supersaturation solution was heated to 150° and filtered out
the suspended insoluble materials. The filtered solution was then
gradually cooled to 70° and kept for 10 h for the growing of seed
crystals. Afterwards, a seed crystal with good quality then was
placed into the saturated precursor solution surrounded by toluene
as antisolvent and kept at room temperature. High-quality,
millimeter-sized CsPbBr3 single crystals were synthesized after
keeping for 7 days.
components of the Bi-doped CsPb1−xBixBr3 (x
) crystals were also
close to the stoichiometric ratios. We also measured XPS of the
CsPbBr3 and the Bi-doped CsPb1−xBixBr3 crystals to confirm the
components (Fig S3). The XPS spectrum of CsPbBr3 crystal indicated
the ratio of Cs: Pb: Br is closed to 1: 1:3, which is consistent with the
EDS result. In the XPS spectra of the Bi-doped CsPb1−xBixBr3 (x
)
crystals, there was an additional peak at 164 eV except the peaks
for Cs, Pb, and Br, which is corresponding to the Bi 4f5/2 component
of Bi3+.26 Another component of Bi3+, Bi 4f7/2, was overlapped with
Cs+ 4P3/2 at 159 eV. The ratio of Bi/Pb was increased in the
CsPb0.9Bi0.1Br3 crystal compared with the CsPb0.975Bi0.025Br3 crystal. It
is noted that the Br element components in the Bi-doped crystals
are slightly larger than that of the CsPbBr3 because of the higher
valence of Bi3+ than Pb2+. For a simple expression, the formulas of
The same way was also applied for preparation of the
CsPb1−xBixBr3 (x
PbBr2 and BiBr3 instead of pure PbBr2 as the initial metallic resource.
A series of CsPb1−xBixBr3 (x ) single crystals were obtained by
) single crystals except for using a mixture of
combining PbBr2 and BiBr3 in molar ratios of Pb/Bi = 39:1 and 9:1.
2.3 Measurement and Characterization
Powder X-ray diffraction (XRD) patterns of the CsPbBr3 and
the Bi-doped CsPb1−xBixBr3 (x
) crystals were approximately
CsPb1−xBixBr3 (x
) were collected by a Bruker D8 diffractometer
denoted as CsPb0.975Bi0.025Br3 and CsPb0.9Bi0.1Br3, respectively.
The crystal structure of the as-grown crystals were analysed by
XRD performed on the single crystal powders. The XRD diffraction
with Cu Kα radiation (λ=1.5406 Å). Absorption spectra of the single
crystals were measured with a UV-vis-NIR spectrophotometer (UV-
3600, Shimadzu). The elemental compositions of the single crystals
were analysed via energy dispersive X-ray spectroscopy (EDS) by
patterns of the CsPbBr and CsPb Bi Br (x
) crystals are shown
3
1
−
x
x
3
in Fig. 1b and 1c, respectively. For the CsPbBr3 single crystals, all of
the diffraction peaks are indexed to a monoclinic perovskite phase
field-emission
scanning
electron
microscopy
(FE-SEM;
(PDF 54-0751) with a= 9.843 Å, b= 6.874Å, and c= 4.127 Å,
α=β= 90°,
Quanta 250FEG). X-ray Photoelectron Spectroscopy (XPS)
measurements were carried out in a RBD upgraded PHI-5000C ESCA
and = 122.61°. The strong peaks at 15.2°, 21.3°, 30.7°, 43.8° are
γ
2 | J. Name., 2012, 00, 1-3
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corresponding to the (001), (010), (002), and (020) lattice planes. Capacitances (c) of the single crystals were determined from the
The diffraction pattern of the single crystal powders matches well capacitance−frequency curves and the ε of single crystals was
with the standard diffraction pattern, indicating high crystallinity of calculated using equation (1):
the CsPbBr3 crystals. The diffraction patterns of the Bi-doped
CsPb1−xBixBr3 (x
) crystals are in good agreement with another
monoclinic perovskite phase (PDF 18-0364), which merely slightly
deviates from the cubic perovskite structure of Pm m (221) space where d and A are the thickness and the area of the single crystals,
group. Comparing to the XRD diffraction pattern of the CsPbBr3, the and ε0 is the vacuum permittivity. The
major peaks of the CsPb1−xBixBr3 (x ) crystals slightly shifted to CsPb0.975Bi0.025Br3 and CsPb0.9Bi0.1Br3 can be generally estimated as
lower 2 , suggesting a lattice shrinkage in the CsPb1−xBixBr3 (x 37, 27 and 25.6 respectively.
ε of CsPbBr3,
θ
)
crystals. This lattice shrinkage might be induced by the substitution
The electronic properties of the single crystals were studied by
of Pb2+ (1.19 Å) by Bi3+ (1.03 Å). It is possible to form a substitutional fabricating simple devices with structure of Au/perovskite single
doping because the radius discrepancy of these two kinds of ions is crystal/Au and testing I–V characteristics of the devices under dark.
not
very
large
(about
13%).
Moreover, All of the three kinds of single crystals showed similar I–V
no characteristic peaks of Bi3+ were found in the XRD patterns of characteristics, as shown in Fig. 4a-c. There are obvious kinks in the
CsPb1−xBixBr3 (x
) crystals, which is also an evidence that the Bi3+ I–V curves and each of the I–V curves is divided into three regions.
ions substituted the Pb2+ ions in the crystal structures. Further When the applied voltage is lower than the first kink point voltage,
comparing the lattice constants of CsPb0.975Bi0.025Br3 (a= 5.82 Å, b= the current increases linearly according to the increase of applied
5.83Å, and c= 5.87 Å,
α
=
γ
= 90°, and
β
γ
=89.99°) andCsPb0.9Bi0.1Br3 (a= voltage (n= 1), demonstrating an Ohmic relationship (I ∝ V)
= 90°, and =89.89°), slightly between I and V. From this region (n= 1), we can generally estimate
5.81 Å, b= 5.82Å, and c= 5.87 Å,
α=
β
shorter lattice constants in CsPb0.9Bi0.1Br3 than CsPb0.975Bi0.025Br3 the conductivity (σ) of CsPbBr3, CsPb0.975Bi0.025Br3 and CsPb0.9Bi0.1Br3
was observed. The slightly decrease in lattice constant is also in to be 2.47×10-8 (Ω cm)-1, 6.75×10-7 (Ω cm)-1, and 8.01×10-7 (Ω cm)-1,
good agreement with the substitution of Pb2+ by Bi3+. We further respectively. The conductivities of CsPb0.975Bi0.025Br3 and
measured TEM of the CsPbBr3 and the Bi-doped CsPb0.975Bi0.025Br3 to CsPb0.9Bi0.1Br3 are obviously higher than that of the pure CsPbBr3,
analysis the crystal structures. As shown in Fig S4, the TEM images which is mainly attributed to higher carrier concentration and lower
demonstrate that the CsPbBr3 and CsPb0.975Bi0.025Br3 crystals are in bandgaps of the Bi-doped perovskites than that of the CsPbBr3
similar shapes. The high-resolution TEM (HRTEM) images show single crystal. With the applied voltage pass through the first kink
clear lattice fringes with of distance 0.41 nm, indicating that the point voltage, the current shows a rapid nonlinear increase (n> 3),
crystals had a perovskite cubic crystal structure, which is well indicating that all of the trap states have been filled by the injected
consistent with the XRD results. The TEM results are in consistent carriers. The voltage at which all the trap states are filled (the first
with the results published in the literature.26
kink point voltage) is defined as the trap-filled limit voltage (VTFL),
which is determined by the trap density: 29
3.2 Optical and electronic properties
The synthesized crystals were big enough for testing their optical
and electronic properties. The absorption spectra of CsPbBr3 and
where e is the elementary charge, and ntrap is the trap density. For
the CsPbBr3 single crystal, the VTFL values is 27.8 V and the trap
density ntrap can be calculated as 2.8×1010 cm-3. The calculated trap
density of CsPbBr3 is very close to that of the MA-based perovskite
CsPb1−xBixBr3 (x
) single crystals are shown in Fig. 2. The CsPbBr3
single crystal demonstrates strong light absorption up to around
560 nm and corresponds to a band gap of about 2.21 eV, which is in
good agreement with previous reports.9 The sharp band edge in the
absorbance spectrum suggests very few in-gap defect states in the
crystal. On the other hand, significant red shifts of the band edge
are observed in the absorption spectra of the Bi-doped
single crystal.21 Using
a similar way, the trap density of
CsPb0.975Bi0.025Br3 and CsPb0.9Bi0.1Br3 are estimated as 3.4×1010 cm-3
and 2.8×1010 cm-3, respectively. The trap density for Bi-doped single
crystals is higher than the CsPbBr3 crystal, which could be related to
the difference in crystal structure, bandgap, electronic structure,
and defect density after the doping of Bi3+ ion. When the biased
voltage higher than the second kink point voltage, the increase of
current exhibits a quadratic dependence on the increase of voltage
(n= 2), fitting well with the Mott's space charge-limited current
(SCLC) theory. The dark current of the perovskite single crystals well
follow Mott-Gurrent Law: 19,30
CsPb1−xBixBr3 (x
) comparing to the CsPbBr3 single crystal. The Bi-
induced bandgap narrowing is consistent with the results reported
recently.27 Previous theoretical studies suggested that the outer ns2
electrons of the doping ions played very important role to modulate
the bandgaps of perovskite materials and the interacting states
introduced by the Bi3+ doping ions might cause the decrease of the
bandgaps.27,28 The band edges of CsPb1−xBixBr3 (x
) crystal are
located at about 700 nm, corresponding to a band gap of about
1.77 eV. With the Bi component increases, the absorption is slightly
improved. The absorption spectra of the CsPb1−xBixBr3 (x
) single
where ꢀ, JD, ε0 ,ε, V and L is the carrier mobility, current density,
crystals cover entirely the visible spectrum, suggesting great
promising of this kind of Bi-doped perovskites for optoelectronic
applications.
vacuum permittivity, relative dielectric constant, applied voltage,
and thickness of the perovskite single crystals, respectively.
According to the Mott-Gurney’s law, we can generally estimate the
carrier mobility of the three kinds of perovskite single crystals to be
13.6, 21.6, and 39.5 cm2V-1S-1, respectively. In addition, the carrier
The relative dielectric constants (ε) of the single crystals were
estimated from the capacitance−frequency measurement (Fig. 3).
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concentrations nc of the perovskite single crystals also can be
estimated by:
respectively (Fig S6). Especially, a great effective photostriction of
about 6.5×10-5 has been achieved for the CsPb0.9Bi0.1Br3 crystal,
which is much higher than that of the previously reported
photostrictive crystals (Table 2). Such high photostrictive effect
makes the Bi-doped inorganic halide perovskites with great
The carrier concentrations of these three perovskite single crystals
thus can be estimated as 1.13×1010, 1.96×1011, and 1.27×1011 cm-3, potential for applications in light-driven-mechanical devices. It is
respectively. The carrier mobility and carrier concentrations of
CsPbBr3 single crystal are comparable to the previously reported
values of MAPbI3 and FAPbI3, as summarized in Table 1. The carrier
concentrations of CsPb0.975Bi0.025Br3 and CsPb0.9Bi0.1Br3 are much
higher than that of CsPbBr3 and MAPbI3, which is in good
agreement with the presence of trivalent Bi ion in the crystals that
donates more holes and leads to the larger carrier density.
worth mentioning that the photostriction values of these crystals
are most likely underestimated because the light only can penetrate
into a depth of several micrometres in the tested crystals. We
further measured the photostriction of CsPb0.9Bi0.1Br3 crystal under
1000 W/m2 illumination with a 650 nm laser. As shown in the 3D
image of the AFM (Fig 6a), the CsPb0.9Bi0.1Br3 crystal exhibited rapid
and reversible size dilatation and the crystal size was greatly dilated
3.3 Photostriction behaviours
more than 600 nm, corresponding to
a huge effective
photostriction of about 8×10-4 (Fig 6b). The photostriction
coefficient (photostriction/light density) was greatly increased to
8×10-7m2/W. The significant increase of photostriction under
illumination of long-wavelength laser also suggested the
wavelength selectivity of the CsPb0.9Bi0.1Br3 crystal for
photostriction, indicating such Bi-doped inorganic halide
perovskites very promising for possible light-driven actuator
applications.
Photostriction phenomenon refers to nonthermal changes in size of
materials under illumination, which is promising for applying in
many future technologies such as advanced remote switchable
devices and light-induced actuators. The photostriction
phenomenon has been widely observed in many kinds of materials
such as ferroelectrics, polar and non-polar semiconductors, and
organic-based materials. Recently, photostriction in the emerging
perovskite-structured materials has received widespread attention.
For example, visible-light-induced size changes in BiFeO3 crystals
have been observed by experimental method.32,33 Numerical
techniques also suggested large photostrictive effects can be
obtained in BiFeO3 crystals.34 Very recently, giant photostrictive
response in hybrid organic–inorganic halide perovskite MAPbI3 was
reported.31 However, photostriction phenomenon in air-stable
inorganic halide perovskites e.g. CsPbBr3 has not been reported yet.
In this work, we evaluate the photostriction performances of the
prepared inorganic halide perovskites under different light
intensity. Single crystals with thickness of 0.44, 0.62 and 0.90 mm
were selected for CsPbBr3, CsPb0.975Bi0.025Br3, and CsPb0.9Bi0.1Br3
Generally, photostriction in ferroelectrics is interpreted as the
combination of
a bulk photovoltaic effect and converse
piezoelectricity.34 The halide perovskites are theoretically and
experimentally considered to be ferroelectric when the structures
are non-centrosymmetric. Considering the non-centrosymmetric
monoclinic structures of CsPb0.975Bi0.025Br3 and CsPb0.9Bi0.1Br3
crystals, ferroelectricity might exist in the Bi-doped inorganic halide
perovskites. Therefore, the photostriction in CsPb0.975Bi0.025Br3 and
CsPb0.9Bi0.1Br3 crystals could be explained by superposition of the
bulk photovoltaic effect and piezoelectricity. The lattice
deformation was induced by an effective electric field that was
formed by spontaneously separating of the photo-generated
carriers with the non-centrosymmetric structures. In addition, in
comparison to the narrow light absorption of CsPbBr3 crystal, the
enhancement of light absorption for long-wavelength light in the Bi-
doped inorganic halide perovskites also helps to lower the
excitation energies for generation of the carriers and thus easier to
deform with lower light energy.
respectively for the photostriction measurements (Fig S5).
A
halogen lamp was used as the light resource and the light was
guided through the AFM built-in optical system onto the surface of
the crystals. The height of the crystals was measured by placing the
AFM tip at the surface of the crystals. The CsPbBr3 single crystal
indicated reproducible size dilation upon white light illumination
and the dilation gradually became more obvious with the increase
of light intensity, as shown in Fig 5a. According to the literature,34
the much slower plateaus in Fig 5 are due to the thermal bending of
the AFM tips. Therefore, we take the instantaneous height leaps as
the light induced size dilatation. The effective photostriction (ꢁH/H)
of about 3×10-5 has been obtained for the CsPbBr3 when the light
intensity was 1000 W/m2. The effective photostriction of CsPbBr3
was much smaller than that of the hybrid organic–inorganic
analogue MAPbI3 crystal.35 This is because the atoms in CsPbBr3
crystal packed more closely with strong covalent and ionic bonds
than the hydrogen bonding in MAPbI3. Such strongly packed atoms
make it energetically costly for the CsPbBr3 lattices to dilate, thus
leading to the poorer photostriction. Unexpectedly, we amazedly
observed significant increase of the effective photostriction in the
Bi-doped CsPb0.975Bi0.025Br3 and CsPb0.9Bi0.1Br3 crystals, as shown in
Fig. 5b and 4c. Comparing to the CsPbBr3 crystal, the effective
photostriction values were increased by 70% and 100%,
Conclusions
We have prepared a series of air-stable inorganic halide perovskite
single crystals, CsPbBr3, CsPb0.975Bi0.025Br3 and CsPb0.9Bi0.1Br3 via a
modified anti-solvent vapour-assisted crystallization method.
Optical absorption measurements demonstrated that the Bi-doped
CsPb0.975Bi0.025Br3 and CsPb0.9Bi0.1Br3 crystals have broad absorption
covering the entirely visible spectrum, making them promising
materials for photovoltaic and other optoelectronic applications.
The low trap density and high carrier mobility of these inorganic
halide perovskites also indicated their great potentials for
applications in high-performance optoelectronic devices. Most
importantly, the Bi-doped CsPb0.975Bi0.025Br3 and CsPb0.9Bi0.1Br3
crystals showed excellent photostriction performances, which will
expand the applications of such kind of perovskites to emerging
applications, such as microactuations and microsensings.
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23 Y. Liu, J. Sun, Z. Yang, D. Yang, X. Ren, H. Xu, Z. Yang and S. F.
Liu, Adv. Opt. Mater., 2016, , 1829-1837.
Acknowledgements
4
24 K. Heidrich, H. Künzel and J. Treusch, Solid State Commun.,
1978, 25, 887-889.
We acknowledge the financial support from the National Natural
Science
Foundation
of
China
(21403112),
the
25 C. C. Stoumpos, C. D. Malliakas, J. A. Peters, Z. Liu, M.
Sebastian, J. Im, T. C. Chasapis, A. C. Wibowo, D. Y. Chung
and A. J. Freeman, Cryst. Growth Des., 2013, 13, 2722-2727.
26 R. Begum, M. R. Parida, A. L. Abdelhady, B. Murali, N. M.
Alyami, G. H. Ahmed, M. N. Hedhili, O. M. Bakr, and O. F.
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27 A. L. Abdelhady, Makhsud I. Saidaminov, B. Murali, V.
Adinolfi, O. Voznyy, K. Katsiev, Erkki Alarousu, R. Comin, I.
Dursun, L. Sinatra, E. H. Sargent, O. F. Mohammed, and
Natural Science Foundation of Jiangsu Province (BK20140778), and
the Fundamental Research Funds for the Central Universities,
No.3091501333 and A Project Funded by the Priority Academic
Program Development of Jiangsu Higher Education Institutions
(PAPD). The AFM and EDS experiments were performed at the
Materials Characterization Facility of Nanjing University of Science
and Technology.
Osman M. Bakr, J. Phys. Chem. Lett., 2016,
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Figures:
Scheme 1. Schematic diagram of the crystals growth process.
Figure 1. (a) Single crystals of CsPbBr3 and CsPbxBi1-xBr3 prepared by a modified antisolvent vapour-assisted crystallization method. (b) X-ray
diffraction pattern of the CsPbBr3 single-crystalline powder. (c) X-ray diffraction patterns of the CsPbxBi1-xBr3 single-crystalline powder.
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Figure 2. UV-vis-NIR absorption spectra of the CsPbBr3 and CsPbxBi1-xBr3 single crystals.
Figure 3. The capacitance dependent frequency curves for the CsPbBr3 and CsPbxBi1-xBr3 single crystals.
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Figure 4. Dark Current–voltage curves of (a) CsPbBr3, (b) CsPb0.975Bi0.025Br3, and (c) CsPb0.9Bi0.1Br3 single crystals for electronic properties
characterization.
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Figure 5. Effective photostriction (ꢁH/H) of (a) CsPbBr3, (b) CsPb0.975Bi0.025Br3, and (c) CsPb0.9Bi0.1Br3 single crystals under different light
density; the photostriction of (a′) CsPbBr3, (b′) CsPb0.975Bi0.025Br3, and (c′) CsPb0.9Bi0.1Br3 single crystals under 1000 W/m2 illumination of
white light.
Figure 6. (a) Photostriction (ꢁH) of the CsPbBr3 single crystal under 1000 W/m2 illumination of a 650 nm laser. (b) Effective photostriction
(ꢁH/H) of the CsPbBr3 single crystal under 1000 W/m2 illumination of the 650 nm laser.
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Table 1 Electronic parameters of different halide perovskite single crystals.
Single crystal
Trap density (ntrap),
Carrier concentration (nc),
Refs
Conductivity (σ),
Carrier mobility (ꢀ),
cm-3
cm-3
cm2 V-1 S-1
(ꢂ cm)-1
2.47×10-8
6.75×10-7
8.01×10-7
1.8×10-8





2.84×1010
3.4×1010
2.83×1010
3.3×1010
5.8×109
1.13×1010
1.96×1011
1.27×1011
2×1010
CsPbBr3
13.6
Current work
CsPb0.975Bi0.025Br3
CsPb0.9Bi0.1Br3
MAPbI3
21.6
Current work
39.5
Current work
2.5
18
18
19
20
20
21
21
5×109∼2×1010
9 (±2) ×109

MAPbBr3
MAPbI3
115, 38
Hole, 164± 25
24
3.6×1010
3×1010
MAPbBr3
MAPbI3
1.4×1010


67.2
5.1×109
MAPbCl3
179
MAPbBr3

hole, 2.6×1010
electron, 1.1×1011
hole, 1.8×109
electron, 4.8×1010
6.2×1011
2.6×1012
1.345×1010

34
hole, 8.8×1011
hole, 3.87×1012
MAPbI3
4.36
21

1.1×10-7
8.9×10-9
1.8×10-8
∼10-8
1.5×109
3.1×1011
2.8×109
∼109
4.4
22
22
23
31
31
α-FAPbI3
δ-FAPbI3
FAPbI3
0.179
hole, 40 ± 5
MAPbBr3


∼10-4

1011∼1012
Bi-doped MAPbBr3
Table 2 Photostrictive performances of different materials.
Light
White light
Photostriction coefficient, (m2/W) Refs
Photostriction, ꢁH/H
3×10-5
3×10-8
Crystals
CsPbBr3 crystal
Current work
5×10-5
5×10-8
CsPb0.975Bi0.025Br3 crystal White light
Current work
6.5×10-5
8×10-4
6.5×10-8
8×10-7
White light
Current work
CsPb0.9Bi0.1Br3 crystal
Laser (650 nm)
White light
Current work
5×10-5
5×10-8
MAPbI3 crystal
Si crystal
35
36
37
38
39
40
33
35
41
42
43
43
43
43
44
45
-6.4×10-6
7.84×10-10
7.5×10-5
4×10-7
-7.56×10-17
Laser
7.84×10-13
∗
Ge crystal




7.5×10-8
∗
CdS crystal
4×10-10
∗
GaAs crystal
SbSI crystal
4×10-5
4×10-8
∗
3×10-5
9.2×10-8
BiFeO3 crystal
MAPbI3 film (4 ꢀm)
BiFeO3 film (35 nm)
PbTiO3 film (20 nm)
As2Se3 film
LED (365 nm)
White light
Laser
1.25×10-3
4.6×10-3
2.5×10-3
6.4×10-2
5.4×10-2
-5.6×10-2
-1.1×10-1
2×10-1
1.25×10-6
1.15×10-17
2.5×10-18
1.6×10-4
Thin films
Laser
White light
White light
White light
White light

1.35×10-4
-1.4×10-4
-2.75×10-4
As2S3 film
Ge2Se3 film
Ge2S3 film
2×10-4
∗
Nematic elastomers
Diarylethenes

-7×10-2
-1.35×10-5
* We use 1,000 W/m2 to calculate the photostrictive coefficients as the light intensity was not reported in the references.
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Table of contents
Air-stable CsPb1−xBixBr3 (0 ≤ x
) perovskite crystals: optoelectronic and
photostriction properties
Xiaoliang Miao,a Ting Qiu,a Shufang Zhang,*a He Ma, a Yanqiang Hu,a Fan Bai,a Zhuangchun Wu*b
Heterovalent Bi-doped CsPb1−xBixBr3 perovskites greatly improve the light absorption and photostriction of CsPbBr3 crystals
.
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Supporting Information
Air-stable CsPb1−xBixBr3 (0 ≤ x
) perovskite crystals: optoelectronic and
photostriction properties
Xiaoliang Miao, Ting Qiu, Shufang Zhang,* He Ma, Yanqiang Hu, Fan Bai, Zhuangchun Wu*
This file includes Figure S1-S6:
Figure S1. Photographs of the (a) CsPbBr3, (b) CsPb0.975Bi0.025Br3, and (c) CsPb0.9Bi0.1Br3 single crystals.
Figure S2. EDS results of the CsPbBr3, CsPb0.975Bi0.025Br3, and CsPb0.9Bi0.1Br3 single crystals.
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Figure S3. XPS spectra of CsPbBr3, CsPb0.975Bi0.025Br3, and CsPb0.9Bi0.1Br3 single crystals.
Figure S4. TEM images of CsPbBr3, CsPb0.975Bi0.025Br3, and CsPb0.9Bi0.1Br3 thin films.
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Figure S5. Schematic diagram of the photostriction measurement procedures.
Figure S6. Comparison of the effective photostriction (ꢁH/H) of CsPbBr3, CsPb0.975Bi0.025Br3, and CsPb0.9Bi0.1Br3 single crystals under 1000
W/m2 illumination of white light.
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