Synthesis of all-inorganic CsPb2Br5 perovskite and determination of its luminescence mechanism

Article abstract of DOI:10.1039/c7ra10693a

All-inorganic cesium lead halide perovskite materials, such as CsPbBr₃ and CsPb₂Br₅, have drawn immense attention recently due to their potential applications in optoelectronics. However, unlike the extensively-studied CsPbBr₃, many of the fundamental properties of CsPb₂Br₅ remain unclear, such as its electronic structure and photoluminescence (PL) mechanism. In this work, we developed a novel environmentally friendly chemical method to synthesize CsPb₂Br₅, where only water and ethanol were used as solvents. The optical property and electronic structure of CsPb₂Br₅ were then examined both experimentally and theoretically. For the first time we found that the band-edge emission of CsPb₂Br₅ was not in the visible range as reported in the literature but rather located in the ultraviolet range. By monitoring the PL property during phase conversion between CsPb₂Br₅ and CsPbBr₃, we propose that previously-reported visible emission might be due to the involvement of CsPbBr₃ during sample preparation. Overall, this study presents a novel green method for the preparation of CsPb₂Br₅ and clarifies the optical properties and electronic structure of CsPb₂Br₅.

Full text of DOI:10.1039/c7ra10693a

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Synthesis of all-inorganic CsPb2Br5 perovskite and
determination of its luminescence mechanism†
Cite this: RSC Adv., 2017, 7, 54002
Jing Li,a Huijie Zhang,a Song Wang,b Debing Long,a Mingkai Li,a Yizhong Guo,a
a
a
Zhicheng Zhong,a Kaifeng Wu,c Duofa Wang
and Tianjin Zhang
*
*
All-inorganic cesium lead halide perovskite materials, such as CsPbBr3 and CsPb2Br5, have drawn immense
attention recently due to their potential applications in optoelectronics. However, unlike the extensively-
studied CsPbBr3, many of the fundamental properties of CsPb2Br5 remain unclear, such as its electronic
structure and photoluminescence (PL) mechanism. In this work, we developed a novel environmentally
friendly chemical method to synthesize CsPb2Br5, where only water and ethanol were used as solvents.
The optical property and electronic structure of CsPb2Br5 were then examined both experimentally and
theoretically. For the first time we found that the band-edge emission of CsPb2Br5 was not in the visible
range as reported in the literature but rather located in the ultraviolet range. By monitoring the PL
property during phase conversion between CsPb2Br5 and CsPbBr3, we propose that previously-reported
visible emission might be due to the involvement of CsPbBr3 during sample preparation. Overall, this
study presents a novel green method for the preparation of CsPb2Br5 and clarifies the optical properties
and electronic structure of CsPb2Br5.
Received 27th September 2017
Accepted 18th November 2017
DOI: 10.1039/c7ra10693a
rsc.li/rsc-advances
Niu et al.6 Many efforts are being attempted to mitigate this
degradation issue but with very limited success.7 As a type of
1. Introduction
perovskite material, the all-inorganic perovskites have recently
been proposed as promising candidates for optoelectronics
because of their higher chemical stability as compared to their
hybrid organic–inorganic counterparts.8–10 Cesium lead halide
(CsPbX3, X ¼ Cl, Br, and I) is the most widely reported material,
which was typically prepared in the range of 140–200 ꢀC by wet
chemical method.11 A variety of optoelectronic devices based on
CsPbX3 have been reported.
Very recently, a new type of inorganic perovskite material,
CsPb2Br5, has been found to also exhibit superior optical
property and potential application in optoelectronic device.12–15
Especially interesting is that unlike CsPbBr3 that requires high
temperature for the synthesis, CsPb2Br5 can be prepared in
a facile way at room temperature, which is very attractive for the
future applications. Yu et al. rst reported on the synthesis of
CsPb2Br5 and its efficient photoluminescence (PL) in the visible
region (512 nm) with a quantum yield of 87%.12 Zhou et al.
demonstrated visible amplied spontaneous emission (ASE)
from CsPb2Br5 microplates with very low pump threshold.13 Sun
et al. reported the formation of CsPb2Br5 as a by-product during
the preparation of CsPbBr3 and also noted an enhancement in
the light emission efficiency of CsPbBr3 LED due to the gener-
ation of CsPb2Br5.14 However, there is a debate about the
luminescence mechanism of inorganic CsPb2Br5 perovskite.
Based on the density functional theory (DFT) simulation as well
as experimental work, it has been noted that the visible light
emission gradually decreases and ultimately disappears
In the recent years, newly emerging metal halide perovskite
crystals, in particular organic–inorganic perovskites such as
CH3NH3PbX3 (X ¼ Cl, Br, and I), have attracted tremendous
scientic attention, thanks to the rapid development of perov-
skite solar cells whose power conversion efficiency already
exceeds 20% since the rst report of 3.81% in the year of 2009.1,2
In addition to the applications in photovoltaics, perovskites are
also reported in high-efficiency light emitting diodes (LEDs),
lasers and photodetectors. From the standpoint of practical
application, however, hybrid organic–inorganic perovskites
suffer from low environmental- and photo-stability due to their
undesirable reaction with water and degradation under UV light
irradiation.3–5 Perovskite solar cells start to degrade within
several hours without encapsulation; the chemical processes
that cause the degradation of perovskite lms were reviewed by
aHubei Collaborative Innovation Center for Advanced Organic Chemical Materials,
Ministry of Education, Key Laboratory of Green Preparation and Application for
Materials, Hubei Provincial Key Laboratory of Polymers, Department of Materials
Science and Engineering, Hubei University, Wuhan 430062, People's Republic of
China. E-mail: duofawang@hotmail.com; zhangtj@hubu.edu.cn
bHubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices,
Hubei University of Arts and Science, Xiangyang, Hubei 441053, China
cState Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical
Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
† Electronic supplementary information (ESI) available: Full video of the chemical
reaction; energy dispersive X-spectroscopy of CsPb2Br5; total energy calculation of
unit cell for each reactant and the resultant chemical eqn (2). See DOI:
10.1039/c7ra10693a
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accompanying the phase conversion from CsPbBr3 to CsPb2Br5.
Jiang et al. emphasized that CsPb2Br5 is an indirect bandgap
semiconductor and PL-inactive.15 Therefore, fundamental
research on the optical property and electronic structure of
CsPb2Br5 is imperative, which is important to explain the
current controversial experimental observations and to explore
its mechanism of luminescence.
In this context, we report a facile method on the fabrication
of tetragonal perovskite, CsPb2Br5 at ambient temperature as
well as its phase conversion between CsPb2Br5 and CsPbBr3. By
precisely controlling the phase conversion and monitoring the
evolution of PL property, we nd that CsPb2Br5 has a bandgap
of 3.13 eV and correspondingly exhibits a band-edge emission
in the ultraviolet region, and hence, the frequently observed
visible PL peak can be attributed to the CsPbBr3 by-product in
CsPb2Br5. These results not only clarify the luminescence
mechanism of CsPb2Br5 being under debate, but also provide
valuable insights for the development of CsPb2Br5 based
photoelectric devices.
3. Results and discussion
The CsPb2Br5 was synthesized via a chemical precipitation
method and the details are described in the Experimental
Section. Briey, cesium acetate (CsAc) was rst dissolved in
a mixed solvent of puried water and ethanol and PbBr2 solid
was added into the above solvent mixture. As shown by the
video (Movie S1) in the ESI,† the reaction is very fast and effi-
cient and results in the formation of CsPb2Br5 just several
seconds aer the addition of PbBr2 which “emits” green light
under UV light irradiation. As CsPb2Br5 does not dissolve well in
water, a precipitate was obtained at the bottom. The obtained
precipitate was further treated with HBr to remove the impuri-
ties and then washed with water. We propose the following
equations representing the chemical reactions involved in the
synthesis, where CsAc is hydrolyzed at rst to generate CsOH,
which then reacts with PbBr2:
CsAc + H2O / CsOH + HAc
CsOH + PbBr2 / CsPb2Br5 + Pb(OH)Br
Pb(OH)Br + HBr / PbBr2 + H2O
(1)
(2)
(3)
2. Experimental
Synthesis of CsPb2Br5
To investigate the possibility of eqn (2), which is crucial for
the formation of CsPb2Br5, the total energy (Et) of the chemical
reaction was calculated by employing rst principles. The
change in total energy (DEt) of ꢂ4.558 eV indicates that the
reaction is exothermic and should occur spontaneously. The
details of calculations can be found in the ESI (Table S1†). The
chemical reaction eqn (1) was conrmed experimentally that
the PH value was changed to 9 aer the CsAc is added to the
mixture solvent of water and ethanol.
CsPb2Br5 nanoplates were synthesized by chemical precipita-
tion conducted at room temperature. Firstly, puried water and
ethanol were mixed to obtain the solvent mixture (total volume
¼ 2 ml, VH O : VEtOH ¼ 1 : 3). CsAc (1 mmol) was added into the
2
above solution and dissolved completely. PbBr2 (2.5 mmol) was
added into CsAc solution and mixed mechanically which
resulted in the formation of CsPb2Br5 as a precipitate at the
bottom of the solution. The precipitate was further treated with
HBr to remove the impurities and then washed with water.
Fig. 1a shows the scanning electron microscopy (SEM)
image, which illustrates that the formed CsPb2Br5 nano-
particles are prone to aggregate to form a cluster. Energy
dispersive spectroscopy (EDS) analysis (Fig. S1 in the ESI†)
reveals the molar ratio of Cs/Pb/Br to be 1/2.1/5.9, which agrees
well with the stoichiometry of the compound.
The crystalline structure was characterized by powder X-ray
diffraction (PXRD) (Fig. 1b). As shown in this gure, all the
diffraction peaks match well with the standard tetragonal phase
of CsPb2Br5 (PDF#25-0211). The presence of small amounts of
PbBr2 has also been noted. The microstructure of CsPb2Br5 was
further characterized by TEM, as shown in Fig. 1c and d. High
resolution TEM reveals the crystalline CsPb2Br5 phase with the
lattice fringe of 0.744 nm, corresponding to the (002) plane of
CsPb2Br5. This is well consistent with the XRD results.
Fig. 2a–e illustrate the detailed structure of CsPb2Br5. The
tetragonal phase of CsPb2Br5 belongs to the space group of
I4/mcm and it exhibits a sandwich structure consisting of
[Pb2Br5]ꢂ layers and intercalated Cs+. The Cs+ ions stay in the
gaps between the two rectangular pyramid grooves, which have
a staggered arrangement. There are two types of bromine atoms
occupying different positions in the cell which combine with
lead atoms forming a Pb–Br coordination polyhedron. One lead
atom and eight bromine atoms make up a hendecahedron.
Characterization of CsPb2Br5
The crystal structure was measured by using a X-ray dif-
fractometer (Bruker D8 Advance) with Cu-Ka radiation
˚
(l ¼ 1.5406 A). The SEM and EDS were measured using
JSM7100F. Absorption spectra were obtained by UV-Visible-NIR
Spectrophotometer (SHIMADZU UV-3600). Edinburgh FLS 980
was used to measure the steady-state uorescence spectrum.
First principle calculations
First-principle calculations were performed on the basis of
density functional theory (DFT) as implemented in the
QUANTUM ESPRESSO code. The exchange and correlation
terms were described using general gradient approximation
(GGA) of Perdew–Burke–Ernzerhof (PBE). The energy cutoff for
the plane wave basis set was 600 eV. The accuracy of self-
consistent eld (SCF) energy convergence and the conver-
gence accuracy of the internal stress of crystal is less than 1.4 ꢁ
10ꢂ5 eV per atom and 0.05 GPa, respectively. For the different
alloy congurations, Monkhorst–Pack grids were determined
automatically for Brillouin zone integration and KPPRA
parameter was set to 1000.
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Fig. 1 (a) SEM images of CsPb2Br5 cluster. (b) PXRD pattern of
tetragonal CsPb2Br5 particles (black dots represent PbBr2). The
intensity is in logarithmic scale. (c) Low-resolution, and (d) high
resolution lattice resolved TEM image of a representative CsPb2Br5
cluster.
Combining ball-and-stick models and polyhedral models
exhibit the tetragonal phase of CsPb2Br5 with an interesting
sandwich structure. DFT-based rst-principles calculations (see
details in the Experimental Section) determined the lattice
constants as: a ¼ b ¼ 0.86 nm and c ¼ 1.59 nm.
The optical absorption and emission spectra of CsPb2Br5 are
shown in Fig. 3a. An obvious absorption edge at 380 nm could
be noted which is different from the previously reported value of
520 nm.12,13 In the PL spectrum, the two luminescence peaks at
385 nm and 460 nm were detected which exhibit a small Stokes
shi as compared to absorption. Fig. 3b gives the plots of
(Ahn)1/2 vs. photo energy, from which a bandgap of 3.13 eV can
be found for CsPb2Br5.
Fig. 2 Crystal structure of tetragonal CsPb2Br5. (a), (b) Top and side
views of ball-and-stick models for CsPb2Br5 unit cell. (c), (d) Top and
side views of polyhedral models for the tetragonal structure of
CsPb2Br5, with sandwiched structure by alternating Cs+ and (Pb2Br5)ꢂ
layers. (e) Schematic of Pb–Br hendecahedron (red ball: Cs+, green
ball: Pb2+, blue ball: Brꢂ).
To reconcile the absorption and emission properties of
CsPb2Br5 observed here with previous reports (band edge at
ꢃ515 nm), we scrutinized the absorption spectrum and indeed
found another weak absorption edge at ꢃ515 nm as highlighted
with the red circle in Fig. 3a. Since two absorption edges were
observed, a reasonable assumption is that the one observed at
515 nm is due to an impurity, the most possible origin of which
would be CsPbBr3 considering that there exists a phase transi-
tion between CsPbBr3 and CsPb2Br5 as well as that the
absorption edge of CsPbBr3 is well known to be located at
515 nm and PbBr2 does not show light emission at room
temperature.16,17
To conrm the above speculation, we annealed CsPb2Br5
sample and measured the phase transition and meanwhile
monitored the associated absorption and PL properties. Fig. 4a
is the PXRD data of CsPb2Br5 annealed at different tempera-
tures. As shown in this gure, the diffraction peaks corre-
sponding to CsPbBr3 and PbBr2 were detected when the sample
was treated with thermal annealing, and the intensity of the
corresponding diffraction peaks increased with annealing
temperature. It indicates that part of the CsPb2Br5 is decom-
posed into CsPbBr3 as shown by eqn (4),
CsPb2Br5 / CsPbBr3 + PbBr2
(4)
XPS characterization results in Fig. 4b reveals that there is no
obvious peak shi of binding energy aer the thermal anneal-
ing due to the same chemical valence of Pb in CsPb2Br5 and
CsPbBr3. The microstructure and composition of the annealed
sample was further revealed by TEM and shown in Fig. 4c and d.
The CsPb2Br5 and CsPbBr3 are clearly observed in the high
resolution TEM, which consistent with XRD results.
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Fig.
4
(a) PXRD pattern of tetragonal CsPb2Br5 particles after
annealing at different temperatures (red squares represent CsPbBr3
(PDF#18-0364), black dots represent PbBr2), sample 1 is of high purity
CsPb2Br5 (black) without annealing, sample 2 is CsPb2Br5 after
annealing at 220 ꢀC (red), sample 3 is CsPb2Br5 after annealing at
400 ꢀC (blue). (b) XPS spectra of the pure as-grown CsPb2Br5 and
annealed composite CsPb2Br5–CsPbBr3 with element Pb 4f. (c) Low-
resolution, and (d) high-resolution TEM image of a representative
CsPb2Br5 cluster after annealing at 400 ꢀC.
Fig. 3 (a) Absorption (black) and PL spectra (blue) of CsPb2Br5 parti-
cles, the PL spectrum under 250 nm excitation. (b) Corresponding
(Ahn)1/2 vs. energy (hn) curve of CsPb2Br5. The optical band gap of
CsPb2Br5 is measured to be ꢃ3.13 eV.
Fig. 5a shows the notable increase in absorption between 380
and 530 nm. This absorption band grows with increasing
annealing temperature. When the sample was annealed at
400 ꢀC, the absorption edge at 380 nm was not distinguishable
any more due to being overwhelmed by the absorption of
CsPbBr3, which might explains the absence of the absorption
edge at 380 nm as observed in previous reports. The consistency
between the PXRD and absorption results demonstrates that
the absorption at 515 nm is indeed induced by CsPbBr3.
The PL spectra in Fig. 5b also shows the luminescence peaks
corresponding to CsPbBr3.11,18 In addition, the position of PL
peak shis from 515 to 530 nm with thermal annealing. This is
ascribed to the size effect. In the as-grown sample, the contents
of CsPbBr3 is too low to be detected by XRD and the grain size
must be very small. Whereas, it could grown into larger size with
the decomposition of CsPb2Br5 aer thermal annealing. The
band structure of CsPb2Br5 was investigated theoretically by
rst principles calculations based on DFT (Fig. 5c). It could be
seen that CsPb2Br5 exhibits an indirect band gap of 3.079 eV
with the conduction band minimum and valence band
maximum at the G and K points respectively. The obtained
bandgap value agrees reasonably well with the value as obtained
from the absorption spectrum.
Fig. 5 (a), (b) Absorption and PL spectra of CsPb2Br5 particles. The
black, red and blue represents the sample of as-grown, annealed at
220 ꢀC, and 400 ꢀC, respectively. The PL excitation is 400 nm. (c) DFT
calculated band structure of CsPb2Br5 with a bandgap of 3.079 eV.
Moreover, we investigated the partial cation exchange of Cs
by Rb to from Cs1ꢂxRbxPb2Br5. When RbAc was introduced
together with CsAc, Cs1ꢂxRbxPb2Br5 compound was successfully
synthesized. As shown in Fig. 6a, the ion exchange by Rb did not
change the crystalline structure but the lattice constant was
reduced due to the smaller atomic radius of Rb. Fig. 6b plots the
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valuable insights for the development of CsPb2Br5 based
optoelectronic devices.
Conflicts of interest
There are no conicts to declare.
Acknowledgements
This work has been supported by National Natural Science
Foundation of China (No. 11174071, 11304088 and 51372180)
and Special Technical Innovation Project of Hubei Province (No.
2016AAA035).
Notes and references
1 W. S. Yang, B. W. Park, E. H. Jung, N. J. Jeon, Y. C. Kim,
D. U. Lee, S. S. Shin, J. Seo, E. K. Kim, J. H. Noh and
S. I. Seok, Science, 2017, 356, 1376.
2 A. Kojima, K. Teshima, Y. Shirai and T. Miyasaka, J. Am.
Chem. Soc., 2009, 131, 6050–6051.
3 J. B. You, L. Meng, T. B. Song, T. F. Guo, Y. Yang,
W. H. Chang, Z. R. Hong, H. J. Chen, H. P. Zhou, Q. Chen,
Y. S. Liu, N. D. Marco and Y. Yang, Nat. Nanotechnol., 2016,
11, 75.
4 Q. D. Tai, P. You, H. Q. Sang, Z. K. Liu, C. L. Hu,
H. L. W. Chan and F. Yan, Nat. Commun., 2016, 7, 11105.
5 W. Z. Li, W. Zhang, S. V. Reenen, R. J. Sutton, J. D. Fan,
A. A. Haghighirad, M. B. Johnston, L. D. Wang and
H. J. Snaith, Energy Environ. Sci., 2016, 9, 490.
Fig. 6 (a) PXRD patterns of the parent CsPb2Br5 particles and anion
exchanged samples with increasing quantities of anion-exchange of
Rbꢂ. (b) Absorption (black) and PL spectra (red) of RbPb2Br5, the PL
spectrum under 250 nm excitation.
6 G. Niu, X. Guo and L. Wang, J. Am. Chem. Soc., 2015, 3, 8970–
8980.
7 T. A. Berhe, W. N. Su, C. H. Chen, C. J. Pan, J. H. Cheng,
H. M. Chen, M. C. Tsai, L. Y. Chen, A. A. Dubale and
B. J. Hwang, Energy Environ. Sci., 2016, 9, 323–356.
8 N. Yantara, S. Bhaumik, F. Yan, D. Sabba, H. A. Dewi,
N. Mathews, P. P. Boix, H. V. Demir and S. Mhaisalkar, J.
Phys. Chem. Lett., 2015, 6, 4360.
absorption and PL spectra of RbPb2Br5. Compared to CsPb2Br5
in Fig. 3a, the absorption and PL are red-shied, indicating that
ion exchange of A-site could be utilized to tune the bandgap and
extend the optical response of Cs1ꢂxRbxPb2Br5 to the visible
range.
9 S. W. Eaton, M. Lai, N. A. Gibson, A. B. Wong, L. Dou, J. Ma,
L. W. Wang, S. R. Leone and P. D. Yang, Proc. Natl. Acad. Sci.
U. S. A., 2016, 113, 1993.
4. Conclusions
In conclusion, we developed a novel environmentally green 10 J. Xue, Y. Gu, Q. S. Shan, Y. S. Zou, J. Z. Song, L. M. Xu,
method to synthesize CsPb2Br5, where only water and ethanol
were used as solvents. The optical property and electronic
Y. H. Dong, J. H. Li and H. B. Zeng, Angew. Chem., Int. Ed.,
2017, 56, 5232.
structure of CsPb2Br5 have been explored experimentally as 11 L. Protesescu, S. Yakunin, M. I. Bodnarchuk, F. Krieg,
well as theoretically. For the rst time, we observed the
R. Caputo, C. H. Hendon, R. X. Yang, A. Walsh and
ultraviolet emission from CsPb2Br5. Employing the technique
M. V. Kovalenko, Nano Lett., 2015, 15, 3692.
of UV-vis absorption, PL, and rst principle calculation, we 12 K. H. Wang, L. Wu, L. Li, H. B. Yao, H. S. Qian and S. H. Yu,
nd that the ultraviolet emission is ascribed to band-edge Angew. Chem., Int. Ed., 2016, 55, 8328.
emission of CsPb2Br5, which has a bandgap of 3.13 eV. The 13 X. S. Tang, Z. P. Hu, W. Yuan, W. Hu, H. B. Shao, D. J. Han,
visible emission at 515 nm that was previously ascribed to
band edge emission of CsPb2Br5 is now unambiguously
J. F. Zheng, J. Y. Hao, Z. G. Zang, J. Du, Y. X. Leng, L. Fang
and M. Zhou, Adv. Opt. Mater., 2016, 5, 1600788.
assigned CsPbBr3, which emerged as a by-product due to 14 X. L. Zhang, B. Xu, J. B. Zhang, Y. Gao, Y. J. Zheng, K. Wang
thermally induced phase conversion between CsPb2Br5 and and X. W. Sun, Adv. Funct. Mater., 2016, 26, 4595.
CsPbBr3. This study not only claries the luminescence 15 G. P. Li, H. Wang, Z. F. Zhu, Y. J. Chang, T. Zhang, Z. H. Song
mechanism of CsPb2Br5 being under debate, but also provides
and Y. Jiang, Chem. Commun., 2016, 52, 11296.
54006 | RSC Adv., 2017, 7, 54002–54007
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16 J. Liang, C. X. Wang, Y. R. Wang, Z. R. Xu, Z. P. Lu, Y. Ma, 17 K. Nitsch, V. Hamplova, M. Nikl, C. Canale, K. Polak and
H. F. Zhu, Y. Hu, C. C. Xiao, X. Yi, G. Y. Zhu, H. L. Lv, M. Rodova, Chem. Phys. Lett., 1996, 258, 518–522.
L. B. Ma, T. Chen, Z. X. Tie, Z. Jin and J. Liu, J. Am. Chem. 18 X. M. Li, Y. Wu, S. L. Zhang, B. Cai, Y. Gu, J. Z. Song and
Soc., 2016, 138, 15829–15832.
H. B. Zeng, Adv. Funct. Mater., 2016, 26, 2435.
This journal is © The Royal Society of Chemistry 2017
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