Lead-Free Hybrid Material with an Exceptional Dielectric Phase Transition Induced by a Chair-to-Boat Conformation Change of the Organic Cation

Article abstract of DOI:10.1021/acs.inorgchem.7b01863

Hybrid organic-inorganic perovskite materials have demonstrated great potential in the field of photovoltaics and photoelectronics. On the basis of the high degree of structural flexibility and compatibility, diverse molecular functional materials have been assembled by modifying the length of the organic components and/or dimensionality of the inorganic frameworks. In this paper, we present a chiral lead-free organic-inorganic hybrid, (piperidinium)₂SbCl₅ (1), which follows the one-dimensional inorganic frameworks of the corner-sharing SbCl₆ octahedra. Strikingly, 1 displays a dielectric phase transition at T_c = 338 K, changing from the chiral space group of P2₁2₁2₁ to polar Pna2₁ upon heating. Crystal structure analyses reveal that an unusual thermally activated conformation change of the piperidinium cations affords the driving force to the phase transition of 1. That is, organic piperidinium moieties display a chairlike conformation below T_c, which transforms to a boatlike structure above T_c. Such an unprecedented change is strongly coupled to the dielectric transition along with notable steplike anomalies, which suggest that 1 could be used as a potential switchable dielectric material. Besides, the temperature-dependent conductivity and theoretical analysis of its electronic structure disclose the semiconducting behavior of 1. This study paves the pathway to the design of new lead-free semiconducting perovskites with targeted properties for optoelectronic application.

Full text of DOI:10.1021/acs.inorgchem.7b01863

Article
Cite This: Inorg. Chem. XXXX, XXX, XXX-XXX
pubs.acs.org/IC
Lead-Free Hybrid Material with an Exceptional Dielectric Phase
Transition Induced by a Chair-to-Boat Conformation Change of the
Organic Cation
†
,‡
†
,†
†
†
†
†
Shiguo Han, Jing Zhang, Zhihua Sun,* Chengmin Ji, Weichuan Zhang, Yuyin Wang, Kewen Tao,
‡
,†
Bing Teng, and Junhua Luo*
†State Key Laboratory of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences,
Fuzhou 350002, P. R. China
‡
College of Physics, Qingdao University, Qingdao 266071, P. R. China
*
S Supporting Information
ABSTRACT: Hybrid organic−inorganic perovskite materials have demon-
strated great potential in the field of photovoltaics and photoelectronics. On
the basis of the high degree of structural flexibility and compatibility, diverse
molecular functional materials have been assembled by modifying the length of
the organic components and/or dimensionality of the inorganic frameworks.
In this paper, we present a chiral lead-free organic−inorganic hybrid,
(
piperidinium) SbCl (1), which follows the one-dimensional inorganic
2 5
frameworks of the corner-sharing SbCl octahedra. Strikingly, 1 displays a
6
dielectric phase transition at T = 338 K, changing from the chiral space group
c
of P2 2 2 to polar Pna2 upon heating. Crystal structure analyses reveal that
1
1
1
1
an unusual thermally activated conformation change of the piperidinium
cations affords the driving force to the phase transition of 1. That is, organic
piperidinium moieties display a chairlike conformation below T , which
c
transforms to a boatlike structure above T . Such an unprecedented change is
c
strongly coupled to the dielectric transition along with notable steplike anomalies, which suggest that 1 could be used as a
potential switchable dielectric material. Besides, the temperature-dependent conductivity and theoretical analysis of its electronic
structure disclose the semiconducting behavior of 1. This study paves the pathway to the design of new lead-free semiconducting
perovskites with targeted properties for optoelectronic application.
INTRODUCTION
been conceived as an effective strategy to construct new
electric-ordered materials.
■
Hybrid organic−inorganic perovskite materials (HOIPMs)
have received extraordinary research attention in the past
decade because of their fascinating potential in optoelectronic
Methylammonium lead halides (i.e., CH NH PbX , with X =
3
3
3
Cl, Br, and I) are the most notable hybrid perovskites and have
1
−7
made a breakthrough of power conversion efficiencies for
applications.
organic and inorganic components, allowing for a high degree
Such hybrids combine the excellent merits of
2
7−32
photovoltaic solar cells.
Remarkable semiconducting
8
,9
properties have been identified in crystals of CH NH PbI ,
3
3
3
of structural tunability and rich physical properties. Usually,
the inorganic frameworks offer opportunities for semiconduct-
ing behavior and a wide range of band gaps.
including large absorption coefficients, outstanding ambipolar
10−12
charge transport, pimping exciton binding energy and high
In contrast,
33−37
tolerance to defects, etc.
In addition, the phase transition
organic counterparts provide the possibility of structural
diversities and dynamic behavior, such as the random motions
and potential ferroelectricity were also observed in
CH NH PbI , which originated from the dynamic disordering
1
3−15
3
3
3
of molecular dipoles.
As a consequence, the flexible
+
38−40
of CH NH3 cations.
38 μC/cm has been theoretically estimated in CH NH PbI ,
and the ferroelectric domain walls were also observed from the
solution-processed thin films.
For instance, a large polarization of
3
organic moieties afford large freedom through low barriers to
reorientation within the lattices, which greatly contribute to
dielectric/ferroelectric responses.
recently reported two-dimensional hybrid perovskites, such as
benzylammonium) PbCl and (cyclohexylammo-
2
∼
3
3
3
16−24
As demonstrated by the
41−47
It was deemed that the
polarization also makes a contribution to their photoelectric
(
2
4
48
behavior. However, all of these hybrid perovskites contain
poisonous metal lead, which will aggravate the pollution
nium) PbBr I , the dramatic order−disorder changes of
2
4−4x 4x
organic components induce their structural phase transitions,
along with giant dielectric responses and ferroelectric proper-
2
5,26
ties.
In this context, the delicate introduction of organic
Received: July 25, 2017
cationic moieties with dynamic reorientations or motions has
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.7b01863
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Inorganic Chemistry
Article
Figure 1. Temperature-dependent heat-flow measurements: (a) DSC; (b) specific heat measurements of 1.
impacts of the environment and become an obstacle for their
further commercialization. As the preliminary indicator, the
phase transition is inseparable for the exploration of ferro-
Powder X-ray Diffraction (PXRD). PXRD was used to check the
phase purity of 1, and the result matches well with the simulated data,
as seen in Figure S1. In addition, a Mini Flex II powder X-ray
diffractometer was used to collect the variable-temperature PXRD
data.
4
9−55
electric materials.
Under this circumstance, it is highly
desirable to explore new lead-free hybrid phase-transition
materials for specified device applications.
We have reported a series of lead-free HOIPMs, such as (N-
Thermal Measurement. A Netzsch DSC 200 F3 calorimeter was
used to record differential scanning calorimetry (DSC) and specific
heat (C ) data. Also, a Netzsch STA 449C unit was used to collect
p
methylpyrrolidinium) Sb Br and (N-methylpyrrolidi-
3
2
9
thermogravimetric and differential thermal analysis (TG/DTA) data.
Dielectric Constant Measurement. Dielectric constant tests
were performed on the pressed-powder pellets that were covered by
silver conducting glue. A Tonghui TH2828A analyzer was used to
record the temperature variability of the real part (ε′) of 1 with a
frequency of 700 kHz.
Single-Crystal X-ray Diffraction. A Super-Nova diffractometer
with Mo Kα radiation (λ = 0.71073 Å) was used to measure the
structure data at room temperature (300 K) and high temperature
5
6,57
nium) Sb Cl Br .
These materials display a structural
3
2
9−9x 9x
phase transition accompanied by remarkable ferroelectric
semiconducting properties. However, all of these phase-
transition mechanisms belong to the order−disorder trans-
formation of organic cations. In a subsequent study, we further
performed the chemical modification of these hybrid perov-
skites for phase-transition properties, and we present a chiral
organic−inorganic hybrid, (piperidinium) SbCl (1), which
2
5
(353 K). Crystallographic data in CIF format are given in the
consists of a one-dimensional (1D) perovskite-like anionic
following: CCDC 1541036 for 300 K and 1541037 for 353 K. The
Crystalclear software package (Rigaku, 2005) was utilized to collect
structure information. The SHELXLTL software package was used to
framework constructed by corner-sharing SbCl coordinated
6
octahedra. More strikingly, compound 1 displays a dielectric
64
phase transition at T = 338 K, transforming from a chiral space
solve and refined variable-temperature crystal structures. Crystallo-
graphic data are listed in Table S1.
c
group of P2 2 2 (below T ) to a polar one of Pna2 (above
1
1
1
c
1
Circular Dichroism (CD) Spectroscopy. Solid-state CD spec-
troscopy of compound 1 was performed on a MOS-450 spectrometer
within a range of 200−500 nm at 295 K using KBr pellets.
Second-Harmonic-Generation (SHG) Measurement. A funda-
mental laser (Vibrant 355 II, OPOTEK) beam with a low divergence
was used to detect the SHG properties of 1 at 295 K.
Ultraviolet−Vis (UV−Vis) Spectrometry. UV−vis diffuse-
reflectance spectrometry was performed on a PerkinElmer Lambda
950 UV−vis−IR spectrophotometer.
Tc). It is unprecedented that its phase transition is induced by
an unusual conformation variation of piperidinium cations,
namely, a “chair-to-boat” change of the spatial conformation.
According to what we know, this might be the first discovery of
a solid-state structural phase transition triggered by concrete
conformation changes. The invertible switching of dielectric
constants between two distinct states discloses its potential as a
58−60
switchable dielectric material.
Because of the chainlike
inorganic framework, 1 exhibits notable semiconducting
properties that are confirmed by the positive temperature-
dependent conductivity and theoretical analysis of the
electronic structure. This study opens up new possibilities of
developing electric-ordered materials accompanied by excellent
Alternating-Current (ac) Conductivity. The electrical property
of ac conductivity (σac) was investigated with a direct-current two-
terminal method using single crystals of 1. The temperature
dependence of conductivity was carried out in the heating mode.
61−63
semiconducting behavior.
RESULTS AND DISCUSSION
■
Thermal Properties. The DSC test is an effective tool to
confirm the existence of an invertible thermally induced phase
EXPERIMENTAL SECTION
Materials and Methods. A single crystal of 1 was synthesized by
slow solvent evaporation at room temperature. First, antimony
■
65−67
transition.
Here, compound 1 was subjected to prelimi-
nary DSC measurement (Figure 1a), which shows an
endothermic peak (338.5 K) in the heating mode and an
exothermic peak (336.0 K) in the cooling mode, revealing an
trichloride salts (SbCl ) were prepared by the reaction of antimony
3
trioxide with excessive hydrochloric acid in a cold bath. After stirring
for 20 min, piperidine was added in the molar ratio of 2:1 with
antimony trioxide to the bath. Then, the reaction mixture was stirred
with heating for 20 min to dissolve the components thoroughly.
Colorless crystals were easily acquired by means of slow evaporation of
the solution. A Vario EL cube elemental analyzer was used to check
the elemental contents (C, H, and N). Calcd: C, 25.48; H, 5.13; N,
invertible phase transition. Besides, from the C −T curve, the
p
existence of a phase transition is further confirmed, as seen in
Figure 1b. The C −T curve shows a sharp peak at 338.5 K,
p
which is in accordance with the DSC result. The enthalpy
(ΔH) related to the endothermic peak was estimated to be
2.166 J/g. Therefore, the total entropy change (ΔS) was
5
.94. Found: C, 25.32; H, 5.03; N, 5.92.
B
DOI: 10.1021/acs.inorgchem.7b01863
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Article
calculated to be 3.0158 J/mol·K by following the equation ΔS
on the solid-state structural phase transition triggered by
concrete conformation changes.
As for the packing structure, 1 is featured by a 1D chainlike
inorganic framework, which is closely linked by piperidinium
cations at both RTP and HTP, as shown in Figure 3. In detail,
=
ΔH/T . The value of N was calculated to be 1.44 in light of
c
the Boltzmann formula ΔS = R ln N (N is the ratio of possible
configurations and R is the gas constant). To our knowledge,
such a value of N implies a more complicated phase transition
68
than the previous order−disorder mechanism (N = 2). For
the sake of convenience, we labeled T as the boundary of the
c
room-temperature phase (RTP) and high-temperature phase
(
HTP). Besides DSC and C studies, the pronounced thermal
p
anomaly was also observed by TG/DTA, further confirming the
phase transitions of 1 (Figure S2).
Crystal Structure Discussion. In order to understand the
mechanism of phase transition between RTP and HTP,
variable-temperature single-crystal X-ray diffraction was carried
out at 300 and 353 K, respectively. The results suggest that the
2
−
asymmetric unit of 1 is made up of one [SbCl5] anion and
two protonated piperidinium cations at both RTP and HTP
(Figure 2). The structure of 1 at RTP belongs to the
Figure 3. 1D structure of 1 (a) at 300 K along the c axis and (b) at 353
K along the a axis. Red imaginary lines represent the N−H···Cl
hydrogen bonds.
the organic piperidinium cations are bonded to an inorganic
anionic framework through N−H··Cl hydrogen bonds (Tables
S2 and S3). It is known that the inorganic frameworks of
HOIPS offer opportunities for semiconducting behavior and a
2
−
wide range of band gaps. For 1, the 1D inorganic [SbCl5]
chain would contribute to its charge-transport properties, just
like some tin- and lead-based perovskites. Moreover, the
trivalent antimony ion is isoelectronic with Sn2+ and Pb , and
the electronegativities and ionic radii of these elements are
similar. Thus, compound 1 is expected to exhibit latent
semiconducting behavior.
2+
Although piperidinium cations of 1 undergo exceptional
chair-to-boat conformation transformation during its phase
transition, the inorganic framework only exhibits tiny changes.
As depicted in Figure 4, the central antimony atoms of SbCl6
Figure 2. Top: Asymmetric units of 1 (a) at 300 K and (b) at 353 K.
Bottom: Conformation transformation of the piperidinium cation.
orthorhombic system with a chiral space group P2 2 2 and a
1
1 1
point group D . The cell parameters of 1 are a = 8.4914(6) Å, b
2
3
=
12.2708(8) Å, c = 18.1989(14) Å, and V = 1896.30(2) Å .
With temperature increasing to the HTP (353 K), 1 still
crystallizes in the orthorhombic system. However, the cell
parameters of 1 change to a = 12.3177(3) Å, b = 18.4433(4) Å,
3
c = 8.3976(3) Å, and V = 1907.76(9) Å . Accordingly, the space
group of 1 transforms from P2 2 2 to Pna2 , and its point
1
1
1
1
group becomes a polar one, C . The remarkable differences of
2ν
the crystallographic space group between RTP and HTP can be
easily comprehended from the microscopic structural changes
of 1 during its phase transition. As is vividly depicted in the
bottom of Figure 2, the piperidinium cation resembles a “chair”
at RTP; however, it becomes to a “boat” when the temperature
rises to HTP. In particular, for the piperidinium cation of 1 at
RTP, the atoms of N1 (or N2) and C3 (or C8) are situated
below and above the coplane, respectively, behaving as a
Figure 4. Corner-sharing SbCl6 octahedra of the 1D inorganic
framework of 1 at 300 K (a) and 353 K (b).
octahedra are coordinated by six bromide atoms, one of which
behaves as the bridging linker. As a result, two SbCl octahedra
6
share one bridging corner (Cl5 at RTP or Cl4 at HTP), and the
corner-sharing SbCl octahedra construct a 1D perovskite-like
6
“chair”. In contrast, at HTP, the atoms move to the same side
inorganic framework. In addition, it is obvious that the
geometry of this structural octahedron is slightly distorted, as
deduced from the difference between the Sb−Cl bond lengths.
Besides, the coordinated distortion can also be confirmed from
of the coplane and the structure of the piperidinium cation
changes to a “boatlike” configuration. That is, 1 undergoes a
chair-to-boat conformation transformation during its phase
transition, which differs from the previous order−disorder
mechanism. To our knowledge, this should be the first report
the different bond angles (Cl−Sb−Cl) of the SbCl irregular
6
octahedra (Table S4).
C
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Article
Variable-Temperature PXRD (VT-PXRD). In general, VT-
PXRD offers the most powerful information on phase-
transition materials. As depicted in Figure 5, the PXRD data
Dielectric Properties. The changes of the dielectric
constants between RTP and HTP represent the degree of
electric polarizability of the materials. So, the temperature-
dependent dielectric constant measurement can be seen as an
indicator for phase transition. Structure analyses have
disclosed the conformation transformation of 1 during its
phase transition. To further confirm this feature, we measured
its temperature-dependent complex dielectric permittivities (ε
7
1
=
ε′ − iε″) in the heating/cooling cycle on pressed-powder
pellets. Figure 6 shows the real part (ε′) of 1 at a frequency of
Figure 5. VT-PXRD patterns of 1. The Miller indexes were calculated
from the single-crystal structure.
collected at RTP (300 and 320 K) and HTP (345 and 355 K)
are in well accordance with relevant simulated data (the black
and purple lines). However, drastic changes were found
between the RTP and HTP data, strongly ensuring the
existence of a phase transition in 1. For instance, as the
Figure 6. Temperature variable of the real part (ε′) of the complex
permittivity for 1.
temperature increases above T , the diffraction peaks at 11.46°,
c
20.94°, 30.83°, 31.23°, 31.94°, and 32.34°, relevant to the Bragg
diffraction patterns of the (010), (200), (042), (134), (232),
and (205) planes at RTP, exhibit obvious shifts toward the
high-angle direction. In addition, the two peaks at 18.00° merge
into one peak as the temperature moves from RTP to HTP.
Generally, the decrease in the number of diffraction peaks
indicates enhancement of the crystal symmetry. The symmetry
transformation of 1 (i.e., from the point group D to C ) agrees
fairly well with this concept. It is obvious that the PXRD data
acquired upon cooling back to 300 K from HTP (the light-
green line) are in accordance with the patterns collected at 300
K (the dark-green line). Such a consequence solidly ensures the
invertible phase transition in 1.
700 kHz within the range of 300−360 K. Obviously, we can see
a couple of steplike dielectric anomalies at 338.5 and 336 K in
the heating and cooling procedure, respectively. This finding is
well compatible with the DSC result. In detail, upon cooling,
the value of ε′ declines from 22 to 15. The value of the
dielectric constant at the HTP state (f = 700 kHz) is ∼40%
larger than that of the RTP state, which discloses that 1 can be
used as a “dielectric switch”. This behavior, that is, the
invertible switching of the dielectric constants between high
and low states, indicates the splendid dielectric switchable
property of 1.
2
2v
Semiconducting Properties. Because the structure of 1
features a 1D inorganic framework, it is expected to display
interesting semiconducting properties. Here, we conducted
UV−vis diffuse-reflectance spectroscopy to explore the semi-
conducting properties of 1. It is common knowledge that the
semiconductor band-gap type can be divided into direct and
indirect band gaps based on its light absorption features. Here,
for convenience, the direct-band-gap semiconductor ZnO was
selected for comparison. As shown in Figure 7, like ZnO, the
UV−vis absorption spectra of 1 exhibit a sharp edge in the
range of the UV spectra, indicating that compound 1 is a direct-
band-gap semiconductor. Theoretical analysis shows the
Solid-State CD Spectra and SHG Characterization. CD
spectroscopy is one of the simple and quick ways to obtain
structural information on molecular crystals. To examine the
chiroptical activities of 1, solid-state CD spectra were
investigated at 295 K. The CD spectra of compound 1 display
a strong Cotton effect around 230 nm (Figure S3), solidly
confirming that 1 belongs to a chirality structure at room
6
9,70
temperature.
single-crystal X-ray diffraction consequences, which disclose
that the space group of 1 is P2 2 2 at RTP. Because compound
This finding is well in accordance with the
1
1 1
72
1
has a chiral space group of P2 2 2 at room temperature,
1 1 1
semiconducting band gap calculated by the Tauc formula:
which belongs to the noncentrosymmetric structure, it is
expected to exhibit interesting a second-order nonlinear-optical
1
/n
[
hνF(R )] = A(hν − Eg)
∞
(NLO) response. Here, we further record the SHG signal of 1
using the fundamental laser beam at 295 K. As depicted in
Figure S4, 1 shows an obvious frequency-doubled signal around
where h is the Planck constant, ν is the vibrational frequency of
the oscillator, F(R ) is the Kubelka−Munk function, A is the
∞
73
532 nm, which is well consistent with its noncentrosymmetric
constant of proportionality, and E is the band gap. The value
g
structure. Specifically speaking, as the standard sample, KDP
was used for comparison. The SHG intensities of 1 were 0.2
times those of KDP, indicating that 1 might be used as a
possible hybrid organic−inorganic NLO material.
of n is based on its band-gap type (n = 2 for the indirect band
1
gap and n = / for the direct band gap). Therefore, the band
2
gap E of 1 can be calculated from the Tauc plot (inset of
g
Figure 7). The estimated band gap is 3.23 eV for 1, comparable
D
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Inorganic Chemistry
Article
Figure 9. Calculated band structure of 1.
Figure 7. UV−vis absorption spectra for 1 and ZnO. Inset: Calculated
band gap of 1.
to other analogues with 1, such as (CH NH )PbCl with a
3
3
3
74
band gap of 2.97 eV.
Moreover, we measured the temperature-dependent con-
ductivity of 1 to explore its semiconducting properties. As
shown in Figure 8, with increasing temperature, the positive
Figure 10. Partial density of states of 1.
2
−
s2p states) overlap completely within the range from −17 to
1 eV. This result reveals intense covalent forces in the N−H
Figure 8. Temperature-dependent conductivity of 1. Inset: Imaginary
part (ε″) of the complex dielectric permittivity of 1.
and C−H bonds. Besides, in the neighborhood of the Fermi
level (E ) of the partial density of states, quite strong overlap is
f
observed between Sb s/p and Br s/p. Moreover, for the whole
energy region (−16 to −12, −9 to 0, and 2.5−5.5 eV), Sb s/p
and Cl s/p overlap distinctly, indicating the intense interactions
in the Sb−Cl bonds. The intensive conduction bands mainly
result from the states of Sb 5p, while the flat valence bands
originate from the Cl 3p states. Such coupling reveals that the
band gap of 1 is determined by the electronic structure of the
1D inorganic chain, resembling some lead- and antimony-based
slope of the conductivity reveals that 1 is a semiconductor. In
addition, the measured temperature-dependent ac conductivity
of 1 is consistent with that of the imaginary part (ε″) of the
dielectric constant (f = 700 kHz; inset of Figure 8), according
to the formula σ = ωε″ε (ω is the circular frequency and ε is
ac
0
0
75,76
the dielectric constant of free space).
Therefore, the
positive slope of the conductivity with increasing temperature
79
and the sharp rise of the absorptivity indicate that 1 is a
perovskite hybrids.
7
7,78
semiconductor.
CONCLUSION
Furthermore, in order to explore the semiconducting
electronic mechanism of 1, we calculated the band structure
and energy gap, making use of density functional theory. As
depicted in Figure 9, the maximum of the valence band and the
minimum of the conduction band are located at the X point,
indicating that 1 is a direct-band-gap semiconductor. This
discovery is in well accordance with the UV−vis absorption
spectral result. In addition, the value of the theoretical band gap
is 3.38 eV, which coincides with the laboratorial value of 3.23
eV.
■
In summary, we have successfully demonstrated one lead-free
hybrid organic−inorganic hybrid, [C H N] [SbCl ], which
5
12
2
5
undergoes a high-temperature phase transition induced by an
unusual chair-to-boat conformation change of the piperidinium
cations. The dielectric constants can be switched between two
distinct states, which discloses its potential as a switchable
dielectric material. In addition, with increasing temperature, the
positive slope of the conductivity suggests that 1 could be used
as a lead-free semiconductor. Theoretical analysis of the
electronic structure and energy gap suggests that 1 displays
Additionally, for the partial density of states of 1, as depicted
in Figure 10, obviously, the organic portions (C 2s, H 1s, and N
direct-band-gap behavior, and the estimated band gap E is 3.38
g
E
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Inorganic Chemistry
Article
eV. Our study opens up new ways to develop electric-ordered
materials accompanied by excellent semiconducting behavior.
S.; Yang, K. L.; Liu, J. M.; Li, J. Y.; Yan, Y. F.; Xiong, R. G. An organic-
inorganic perovskite ferroelectric with large piezoelectric response.
Science 2017, 357, 306−309.
(8) Mitzi, D. B.; Field, C. A.; Harrison, W. T.; Guloy, A. M.
ASSOCIATED CONTENT
Supporting Information
■
Conducting tin halides with a layered organic-based perovskite
*
S
structure. Nature 1994, 369, 467−469.
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.7b01863.
(9) Mitzi, D. B.; Wang, S.; Field, C. A.; Chess, C. A.; Guloy, A. M.
Conducting Layered Organic-inorganic Halides Containing < 110>-
Oriented Perovskite Sheets. Science 1995, 267, 1473−1476.
Experimental and calculated PXRD patterns, TG/DTA
curves, CD spectra, experimental SHG signal, crystal data
and structure refinement, hydrogen bonds, and bond
angles (PDF)
(10) Takahashi, Y.; Obara, R.; Nakagawa, K.; Nakano, M.; Tokita, J.
Y.; Inabe, T. Tunable Charge Transport in Soluble Organic−Inorganic
Hybrid Semiconductors. Chem. Mater. 2007, 19, 6312−6316.
(11) Scaife, D. E.; Weller, P. F.; Fisher, W. G. Crystal preparation and
properties of cesium tin(II) trihalides. J. Solid State Chem. 1974, 9,
308−314.
(12) Chung, I.; Song, J. H.; Im, J.; Androulakis, J.; Malliakas, C. D.;
Accession Codes
CCDC 1541036−1541037 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
Li, H.; Freeman, A. J.; Kenney, J. T.; Kanatzidis, M. G. CsSnI :
3
Semiconductor or Metal? High Electrical Conductivity and Strong
Near-Infrared Photoluminescence from a Single Material. High Hole
Mobility and Phase-Transitions. J. Am. Chem. Soc. 2012, 134, 8579−
8
(
587.
13) Kinbara, K.; Aida, T. Toward Intelligent Molecular Machines:
Directed Motions of Biological and Artificial Molecules and
AUTHOR INFORMATION
Corresponding Authors
E-mail: sunzhihua@fjirsm.ac.cn.
E-mail: jhluo@fjirsm.ac.cn.
■
Assemblies. Chem. Rev. 2005, 105, 1377−1400.
(14) Dominguez, Z.; Khuong, T. A.; Dang, H.; Sanrame, C. N.;
*
̃
Nunez, J. E.; Garcia-Garibay, M. A. Molecular Compasses and
Gyroscopes with Polar Rotors: Synthesis and Characterization of
*
Crystalline Forms. J. Am. Chem. Soc. 2003, 125, 8827−8837.
ORCID
(
15) Leigh, D. A.; Wong, J. K.; Dehez, F.; Zerbetto, F. Unidirectional
Junhua Luo: 0000-0002-7673-7979
Notes
The authors declare no competing financial interest.
rotation in a mechanically interlocked molecular rotor. Nature 2003,
24, 174−179.
16) Akutagawa, T.; Koshinaka, H.; Sato, D.; Takeda, S.; Noro, S. I.;
4
(
Takahashi, H.; Kumai, R.; Tokura, Y.; Nakamura, T. Ferroelectricity
and polarity control in solid-state flip-flop supramolecular rotators.
Nat. Mater. 2009, 8, 342−347.
ACKNOWLEDGMENTS
This work was supported by the NSFC (Grants 21601188,
1525104, 21571178, 21622108, 91422301, 21373220,
1402296, 51502288, and 51502290), the Strategic Priority
Research Program of the Chinese Academy of Sciences (Grant
XDB20000000), and the Youth Innovation Promotion of CAS
Grant 2014262). Z.S. acknowledges support from the State
Key Laboratory of Luminescence and Applications (Grant
SKLA-2016-09).
■
(
17) Frost, J. M.; Butler, K. T.; Brivio, F.; Hendon, C. H.; van
2
5
Schilfgaarde, M.; Walsh, A. Atomistic Origins of High-Performance in
Hybrid Halide Perovskite Solar Cells. Nano Lett. 2014, 14, 2584−
2
590.
(18) Juarez-Perez, E. J.; Sanchez, R. S.; Badia, L.; Garcia-Belmonte,
(
G.; Kang, Y. S.; Moera-Sero, I.; Bisquert, J. Photoinduced Giant
Dielectric Constant in Lead Halide Perovskite Solar Cells. J. Phys.
Chem. Lett. 2014, 5, 2390−2394.
(19) Sato, O. Dynamic molecular crystals with switchable physical
DEDICATION
■
properties. Nat. Chem. 2016, 8, 644−656.
Dedicated to the 80th birthday for Prof. Academician Xin-Tao
Wu from FJIRSM, CAS.
(20) Zhang, W.; Xiong, R. G. Ferroelectric Metal−Organic
Frameworks. Chem. Rev. 2012, 112, 1163−1195.
(21) Zhang, Y.; Liao, W. Q.; Fu, D. W.; Ye, H. Y.; Chen, Z. N.;
Xiong, R. G. Highly Efficient Red-Light Emission in An Organic−
REFERENCES
■
Inorganic Hybrid Ferroelectric: (Pyrrolidinium)MnCl . J. Am. Chem.
3
(
1) Saparov, B.; Mitzi, D. B. Organic−Inorganic Perovskites:
Structural Versatility for Functional Materials Design. Chem. Rev.
Soc. 2015, 137, 4928−4931.
(
22) Sun, Z. H.; Chen, T. L.; Luo, J. H.; Hong, M. C.
2
(
016, 116, 4558−4596.
2) Green, M. A.; Ho-Baillie, A.; Snaith, H. J. The emergence of
perovskite solar cells. Nat. Photonics 2014, 8, 506−514.
3) Møller, C. K. Crystal Structure and Photoconductivity of Cæsium
Plumbohalides. Nature 1958, 182, 1436−1436.
4) Zhu, H. M.; Fu, Y. P.; Meng, F.; Wu, X. X.; Gong, Z. Z.; Ding, Q.;
Bis(imidazolium) L-Tartrate: A Hydrogen-Bonded Displacive-Type
Molecular Ferroelectric Material. Angew. Chem., Int. Ed. 2012, 51,
3
(
871−3876.
(
23) Sun, Z. H.; Luo, J. H.; Chen, T. L.; Li, L. N.; Xiong, R. G.; Tong,
M. L.; Hong, M. C. Distinct Molecular Motions in a Switchable
Chromophore Dielectric 4-N,N-Dimethylamino-4-N-methylstilbazo-
lium Trifluoromethanesulfonate. Adv. Funct. Mater. 2012, 22, 4855−
(
Gustafsson, M. V.; Trinh, M. T.; Jin, S.; Zhu, X. Y. Lead halide
perovskite nanowire lasers with low lasing thresholds and high quality
factors. Nat. Mater. 2015, 14, 636−642.
4
(
861.
24) Sun, Z. H.; Tang, Y. Y.; Zhang, S. Q.; Ji, C. M.; Chen, T. L.;
(
5) Gao, P.; Gratzel, M.; Nazeeruddin, M. K. Organohalide lead
Luo, J. H. Ultrahigh Pyroelectric Figures of Merit Associated with
Distinct Bistable Dielectric Phase Transition in a New Molecular
Compound: Di-n-Butylaminium Trifluoroacetate. Adv. Mater. 2015,
27, 4795−4801.
(25) Liao, W. Q.; Zhang, Y.; Hu, C. L.; Mao, J. G.; Ye, H. Y.; Li, P. F.;
Huang, S. D.; Xiong, R. G. A lead-halide perovskite molecular
ferroelectric semiconductor. Nat. Commun. 2015, 6, 7338.
perovskites for photovoltaic applications. Energy Environ. Sci. 2014, 7,
448−2463.
6) Snaith, H. J. Perovskites: The Emergence of a New Era for Low-
Cost, High-Efficiency Solar Cells. J. Phys. Chem. Lett. 2013, 4, 3623−
630.
7) You, Y. M.; Liao, W. Q.; Zhao, D. W.; Ye, H. Y.; Zhang, Y.; Zhou,
Q. H.; Niu, X. H.; Wang, J. L.; Li, P. F.; Fu, D. W.; Wang, Z. M.; Gao,
2
(
3
(
F
DOI: 10.1021/acs.inorgchem.7b01863
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(
26) Ye, H. Y.; Liao, W. Q.; Hu, C. L.; Zhang, Y.; You, Y. M.; Mao,
(44) Fan, Z.; Xiao, J.; Sun, K.; Chen, L.; Hu, Y.; Ouyang, J.; Ong, K.
J.G.; Li, P. F.; Xiong, R. G. Bandgap Engineering of Lead-Halide
P.; Zeng, K.; Wang, J. Ferroelectricity of CH NH PbI Perovskite. J.
3
3
3
Perovskite-Type Ferroelectrics. Adv. Mater. 2016, 28, 2579−2586.
Phys. Chem. Lett. 2015, 6, 1155−1161.
(
27) Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith,
(45) Meng, X.; Zhang, R. F.; Fu, Z. H.; Zhang, Q. F. Domain-
dependent electronic structure and optical absorption property in
hybrid organic−inorganic perovskite. Phys. Chem. Chem. Phys. 2016,
18, 27358−27365.
H. J. Efficient Hybrid Solar Cells Based on Meso-Superstructured
Organometal Halide Perovskites. Science 2012, 338, 643−647.
(
28) Stranks, S. D.; Eperon, G. E.; Grancini, G.; Menelaou, C.;
Alcocer, M. J.; Leijtens, T.; Herz, L. M.; Petrozza, A.; Snaith, H. J.
Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an
Organometal Trihalide Perovskite Absorber. Science 2013, 342, 341−
(46) Rothmann, M. U.; Li, W.; Zhu, Y.; Bach, U.; Spiccia, L.;
Etheridge, J.; Cheng, Y. B. Direct observation of intrinsic twin domains
in tetragonal CH NH PbI . Nat. Commun. 2017, 8, 14547.
3
3
3
3
(
44.
29) Yang, W. S.; Noh, J. H.; Jeon, N. J.; Kim, Y. C.; Ryu, S.; Seo, J.;
(47) Kutes, Y.; Ye, L.; Zhou, Y.; Pang, S.; Huey, B. D.; Padture, N. P.
Direct Observation of Ferroelectric Domains in Solution-Processed
CH NH PbI Perovskite Thin Films. J. Phys. Chem. Lett. 2014, 5,
Seok, S. I. High-performance photovoltaic perovskite layers fabricated
3
3
3
through intramolecular exchange. Science 2015, 348, 1234−1237.
3
(
335−3339.
(
30) Jeon, N. J.; Noh, J. H.; Yang, W. S.; Kim, Y. C.; Ryu, S.; Seo, J.;
48) Stroppa, A.; Di Sante, D.; Barone, P.; Bokdam, M.; Kresse, G.;
Seok, S. I. Compositional engineering of perovskite materials for high-
Franchini, C.; Whangbo, M. H.; Picozzi, S. Tunable ferroelectric
polarization and its interplay with spin−orbit coupling in tin iodide
perovskites. Nat. Commun. 2014, 5, 5900.
(49) Harada, J.; Shimojo, T.; Oyamaguchi, H.; Hasegawa, H.;
Takahashi, Y.; Satomi, K.; Suzuki, Y.; Kawamata, J.; Inabe, T.
Directionally tunable and mechanically deformable ferroelectric
crystals from rotating polar globular ionic molecules. Nat. Chem.
performance solar cells. Nature 2015, 517, 476−480.
(
31) Etgar, L.; Gao, P.; Xue, Z. S.; Peng, Q.; Chandiran, A. K.; Liu,
B.; Nazeeruddin, M. K.; Grat
Heterojunction Solar Cells. J. Am. Chem. Soc. 2012, 134, 17396−
7399.
32) Hsu, H. Y.; Ji, L.; Ahn, H. S.; Zhao, J.; Yu, E. T.; Bard, A. J. A
̈
zel, M. Mesoscopic CH NH PbI /TiO
3 3 3 2
1
(
Liquid Junction Photoelectrochemical Solar Cell Based on p-Type
2
(
016, 8, 946−952.
MeNH PbI Perovskite with 1.05 V Open-Circuit Photovoltage. J. Am.
3
3
50) Bennett, T. D.; Cheetham, A. K.; Fuchs, A. H.; Coudert, F. X.
Chem. Soc. 2015, 137, 14758−14764.
Interplay between defects, disorder and flexibility in metal-organic
(
33) Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal
frameworks. Nat. Chem. 2016, 9, 11−16.
Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J.
Am. Chem. Soc. 2009, 131, 6050−6051.
(51) Yin, Y. W.; Burton, J. D.; Kim, Y. M.; Borisevich, A. Y.;
Pennycook, S. J.; Yang, S. M.; Noh, T. W.; Gruverman, A.; Li, X. G.;
Tsymbal, E. Y.; Li, Q. Enhanced tunnelling electroresistance effect due
to a ferroelectrically induced phase transition at a magnetic complex
oxide interface. Nat. Mater. 2013, 12, 397−402.
(
34) Cho, H.; Jeong, S. H.; Park, M. H.; Kim, Y. H.; Wolf, C.; Lee, C.
L.; Heo, G. H.; Sadhanala, A.; Myoung, N.; Yoo, S.; Im, S. H.; Friend,
R. H.; Lee, T. W. Overcoming the electroluminescence efficiency
limitations of perovskite light-emitting diodes. Science 2015, 350,
(52) Zhang, W. Y.; Tang, Y. Y.; Li, P. F.; Shi, P. P.; Liao, W. Q.; Fu,
1
(
222−1225.
D. W.; Ye, H. Y.; Zhang, Y.; Xiong, R. G. Precise Molecular Design of
High-Tc 3D Organic-Inorganic Perovskite Ferroelectric: [MeHdabco]-
RbI3 (MeHdabco = N-Methyl-1,4-diazoniabicyclo[2.2.2]octane). J.
Am. Chem. Soc. 2017, 139, 10897−10902.
35) Pathak, S.; Sakai, N.; Wisnivesky Rocca Rivarola, F.; Stranks, S.
D.; Liu, J.; Eperon, G. E.; Ducati, C.; Wojciechowski, K.; Griffiths, J.
T.; Haghighirad, A. A.; Pellaroque, A.; Friend, R. H.; Snaith, H. J.
Perovskite Crystals for Tunable White Light Emission. Chem. Mater.
(53) Pan, Q.; Liu, Z. B.; Tang, Y. Y.; Li, P. F.; Ma, R. W.; Wei, R. Y.;
2
(
015, 27, 8066−8075.
36) Deschler, F.; Price, M.; Pathak, S.; Klintberg, L. E.; Jarausch, D.-
D.; Higler, R.; Huttner, S.; Leijtens, T.; Stranks, S. D.; Snaith, H. J.;
Atature, M.; Phillips, R. T.; Friend, R. H. High Photoluminescence
Zhang, Y.; You, Y. M.; Ye, H. Y.; Xiong, R. G. A Three-Dimensional
Molecular Perovskite Ferroelectric: (3-Ammoniopyrrolidinium)RbBr3.
J. Am. Chem. Soc. 2017, 139, 3954−957.
̈
̈
(54) Xu, W. J.; Li, P. F.; Tang, Y. Y.; Zhang, W. X.; Xiong, R. G.;
Efficiency and Optically Pumped Lasing in Solution-Processed Mixed
Chen, X. M. A Molecular Perovskite with Switchable Coordination
Bonds for High-Temperature Multiaxial Ferroelectrics. J. Am. Chem.
Soc. 2017, 139, 6369−6375.
Halide Perovskite Semiconductors. J. Phys. Chem. Lett. 2014, 5, 1421−
1
426.
(
37) Sutherland, B. R.; Hoogland, S.; Adachi, M. M.; Wong, C. T.;
(55) Shi, P. P.; Tang, Y. Y.; Li, P. F.; Liao, W. Q.; Wang, Z. X.; Ye,
Sargent, E. H. Conformal Organohalide Perovskites Enable Lasing on
Q.; Xiong, R. G. Symmetry breaking in molecular ferroelectrics. Chem.
Soc. Rev. 2016, 45, 3811−3827.
Spherical Resonators. ACS Nano 2014, 8, 10947−10952.
(
38) Deretzis, L.; La Magna, A. L. Exploring the orthorhombic−
(56) Sun, Z. H.; Zeb, A.; Liu, S. J.; Ji, C. M.; Khan, T.; Li, L. N.;
tetragonal phase transition in CH NH PbI : the role of atom kinetics.
3
3
3
Hong, M. C.; Luo, J. H. Exploring a Lead-free Semiconducting Hybrid
Ferroelectric with a Zero-Dimensional Perovskite-like Structure.
Angew. Chem., Int. Ed. 2016, 55, 11854−11858.
Nanoscale 2017, 9, 5896−5903.
(
39) Chen, T.; Foley, B. J.; Ipek, B.; Tyagi, M.; Copley, J. R.; Brown,
C. M.; Choi, J. J.; Lee, S. H. Rotational dynamics of organic cations in
(57) Ji, C.; Sun, Z.; Zeb, A.; Liu, S.; Zhang, J.; Hong, M.; Luo, J.
the CH NH PbI perovskite. Phys. Chem. Chem. Phys. 2015, 17,
3
3
3
Bandgap Narrowing of Lead-Free Perovskite-Type Hybrids for Visible-
Light-Absorbing Ferroelectric Semiconductors. J. Phys. Chem. Lett.
3
(
1278−31286.
40) Guo, Z.; Yoon, S. J.; Manser, J. S.; Kamat, P. V.; Luo, T.
2
(
017, 8, 2012−2018.
Structural Phase- and Degradation-Dependent Thermal Conductivity
58) Zhang, X.; Shao, X. D.; Li, S. C.; Cai, Y.; Yao, Y. F.; Xiong, R.
of CH NH PbI Perovskite Thin Films. J. Phys. Chem. C 2016, 120,
3
3
3
G.; Zhang, W. Dynamics of a caged imidazolium cation−toward
understanding the order-disorder phase transition and the switchable
dielectric constant. Chem. Commun. 2015, 51, 4568−4571.
(59) Li, P.; Yang, X.; Maβ, T. W. W.; Hanss, J.; Lewin, M.; Michel, A.
K. U.; Wuttig, M.; Taubner, T. Reversible optical switching of highly
confined phonon−polaritons with an ultrathin phase-change material.
Nat. Mater. 2016, 15, 870−875.
(60) Raeliarijaona, A.; Fu, H. Persistence of strong and switchable
ferroelectricity despite vacancies. Sci. Rep. 2017, 7, 41301.
(61) Itkis, M. E.; Chi, X.; Cordes, A. W.; Haddon, R. C. Magneto-
Opto-Electronic Bistability in a Phenalenyl-Based Neutral Radical.
Science 2002, 296, 1443−1445.
6
(
394−6401.
41) Stoumpos, C. C.; Malliakas, C. D.; Kanatzidis, M. G.
Semiconducting Tin and Lead Iodide Perovskites with Organic
Cations: Phase Transitions, High Mobilities, and Near-Infrared
Photoluminescent Properties. Inorg. Chem. 2013, 52, 9019−9038.
(
42) Stroppa, A.; Quarti, C.; De Angelis, F.; Picozzi, S. Ferroelectric
Polarization of CH NH PbI : A Detailed Study Based on Density
3
3
3
Functional Theory and Symmetry Mode Analysis. J. Phys. Chem. Lett.
015, 6, 2223−2231.
43) Rohm, H.; Leonhard, T.; Hoffmann, M. J.; Colsmann, A.
2
(
̈
Ferroelectric domains in methylammonium lead iodide perovskite
thin-films. Energy Environ. Sci. 2017, 10, 950−955.
G
DOI: 10.1021/acs.inorgchem.7b01863
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(
62) Kahn, O.; Martinez, C. J. Spin-Transition Polymers: From
Molecular Materials Toward Memory Devices. Science 1998, 279, 44−
8.
63) Bibes, M.; Barthel
electric memory. Nat. Mater. 2008, 7, 425−426.
64) Sheldrick, G. M. SHELXL-97: Programs for X-ray Crystal; Bruker
AXS: Madison, WI, 1997.
65) Wang, D. Y.; Qin, L. L.; Hou, X. L.; Ye, H. Y. Temperature-
4
(
́ ́
emy, A. Multiferroics: Towards a magneto-
(
(
triggered phase transition in pyridazine hexafluorophosphate. Chin.
Chem. Lett. 2015, 26, 145−148.
(
66) Wang, H. T.; Kong, L. H.; Shi, P. P.; Li, Q.; Ye, Q.; Fu, D. W.
The structure and dielectric properties of ionic compounds with
flexible ammonium moiety. Chin. Chem. Lett. 2015, 26, 382−386.
(
67) Wang, F. F.; Chen, C.; Zhang, Y.; Fu, D. W. Crystal structure
and dielectric property of supramolecular macrocyclic [(NDPA)·(18-
2+
+
−
crown-6)] ·(DMA) ·3ClO assemblies. Chin. Chem. Lett. 2015, 26,
4
3
(
1−35.
68) Zhang, W.; Cai, Y.; Xiong, R. G.; Yoshikawa, H.; Awaga, K.
Exceptional Dielectric Phase Transitions in a Perovskite-Type Cage
Compound. Angew. Chem., Int. Ed. 2010, 49, 6608−6610.
(
69) Lin, L.; Yu, R.; Yang, W.; Wu, X. Y.; Lu, C. Z. A Series of Chiral
Metal−Organic Frameworks Based on Oxalyl Retro-Peptides: Syn-
thesis, Characterization, Dichroism Spectra, and Gas Adsorption. Cryst.
Growth Des. 2012, 12, 3304−3311.
(
70) Govorov, A. O.; Fan, Z.; Hernandez, P.; Slocik, J. M.; Naik, R. R.
Theory of Circular Dichroism of Nanomaterials Comprising Chiral
Molecules and Nanocrystals: Plasmon Enhancement, Dipole Inter-
actions, and Dielectric Effects. Nano Lett. 2010, 10, 1374−1382.
(
71) Fro
Press: Oxford, U.K., 1965.
72) Tauc, J.; Grigorovici, R.; Vancu, A. Optical Properties and
Electronic Structure of Amorphous Germanium. Phys. Status Solidi B
966, 15, 627−637.
73) Kortum, G.; Braun, W.; Herzog, G. Prinzip und Meßmethodik
der diffusen Reflexionsspektroskopie. Angew. Chem. 1963, 75, 653−
61.
74) Liu, Y. C.; Yang, Z.; Cui, D.; Ren, X. D.; Sun, J. K.; Liu, X. J.;
̈
hlich, H. Theory of dielectrics, 2nd ed.; Oxford University
(
1
(
̈
6
(
Zhang, J. R.; Wei, Q. B.; Fan, H. B.; Yu, F. Y.; Zhang, X.; Zhao, C. M.;
Liu, S. D. Two-Inch-Sized Perovskite CH NH PbX (X = Cl, Br, I)
3
3
3
Crystals: Growth and Characterization. Adv. Mater. 2015, 27, 5176−
183.
75) Kuang, W.; Nelson, S. O. Low-frequency dielectric properties of
biological tissues: a review with some new insights. Trans. ASAE 1998,
1, 173−184.
76) Kremer, F.; Schonhals, A. Broadband Dielectric Spectroscopy;
Springer: Berlin, 2002.
77) Yuan, Y. B.; Li, T.; Wang, Q.; Xing, J.; Gruverman, A.; Huang, J.
5
(
4
(
(
S. Anomalous photovoltaic effect in organic-inorganic hybrid perov-
skite solar cells. Sci. Adv. 2017, 3, e1602164.
(
78) Xu, Y. X.; Ye, Y.; Liu, T. F.; Wang, X. L.; Zhang, B. Q.; Wang,
M.; Han, H. X.; Li, C. Unraveling a Single-Step Simultaneous Two-
Electron Transfer Process from Semiconductor to Molecular Catalyst
in a CoPy/CdS Hybrid System for Photocatalytic H Evolution under
2
Strong Alkaline Conditions. J. Am. Chem. Soc. 2016, 138, 10726−
1
0729.
(
79) Yin, W. J.; Yang, J. H.; Kang, J.; Yan, Y.; Wei, S. H. Halide
perovskite materials for solar cells: a theoretical review. J. Mater. Chem.
A 2015, 3, 8926−8942.
H
DOI: 10.1021/acs.inorgchem.7b01863
Inorg. Chem. XXXX, XXX, XXX−XXX