Excellent microwave absorption of lead halide perovskites with high stability

Article abstract of DOI:10.1039/c8tc00683k

Given the remarkable progress in physical and structural performances of organic-inorganic lead halide perovskites as a superstar in the photovoltaic field, the study of some of their intrinsic properties is still missing. Herein, we report the microwave absorption performance of MAPbX₃ (MA = CH₃NH₃⁺, X = I^-, Br^- or Cl^-) perovskite crystals in terms of complex permittivity and permeability. We find that the MAPbI₃, MAPbBr₃ and MAPbCl₃ perovskites possess excellent microwave absorbability, and the optimum reflection losses reach -55.23, -54.70 and -46.44 dB at 16.77, 15.46 and 13.54 GHz with a matching thickness of 1.62, 1.76 and 1.95 mm, respectively. Thereafter, we explore the absorption mechanism and find that the microwave absorption properties can be ascribed to the combination of dielectric loss and magnetic loss, but mainly dielectric loss. In addition, the stability of microwave absorbability is also investigated and it is proved to depend significantly on the decomposition of corresponding perovskites. These results highlight the importance of the discovery of microwave absorbability of organic-inorganic lead halide perovskites. More importantly, our study provides perovskite absorbers as a new variable to be considered in the quest for future microwave devices.

Full text of DOI:10.1039/c8tc00683k

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ISSN 2050-7526
PAPER
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Nguyên T. K. Thanh, Xiaodi Su et al.
Fine-tuning of gold nanorod dimensions and plasmonic properties using
the Hofmeister effects
rsc.li/materials-c

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JPolueransael odfoMnaotetraiadljsuCsht emmairsgtriynsC
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DOI: 10.1039/C8TC00683K
Journal of Materials Chemistry C
ARTICLE
Excellent microwave absorption of lead halide perovskites with
high stability
Heng Guo,a Jian Yang,a Bingxue Pu,a Haiyuan Chen,a Yulan Li,a Zhiming Wang,b and Xiaobin Niu*a,b
Received 00th January 20xx,
Accepted 00th January 20xx
Given the remarkable progress in physical and structural performances of organic-inorganic lead halide perovskites as a
superstar in the photovoltaic field, the study of some of their intrinsic properties are still missing. Herein, we report the
microwave absorption performance in MAPbX3 (MA = CH3NH3 , X = I-, Br- or Cl-) perovskite crystals in terms of complex
DOI: 10.1039/x0xx00000x
+
www.rsc.org/
permittivity and permeability. We find that the MAPbI3, MAPbBr3 and MAPbCl3 perovskites possess excellent microwave
absorbability, and the optimum reflect losses reach -55.23, -54.70 and -46.44 dB at 16.77, 15.46 and 13.54 GHz with a
matching thickness of 1.62, 1.76 and 1.95 mm, respectively. Thereafter, we explore the absorption mechanism and find that
the microwave absorption properties are ascribed to the combination of dielectric loss and magnetic loss, but mainly for
dielectric loss. In addition, the stability of microwave absorbability is also investigated and it is proved to be significantly
depend on the decomposition of corresponding perovskites. These results highlight the importance to the discovery of
microwave absorbability in organic-inorganic lead halide perovskites. More importantly, our study provides perovskite
absorbers as a new variable to be considered in the quest for future microwave devices.
communication systems, but also for military affairs, such as mobile
phone, wireless local area network, satellite broadcast systems, and so
on.24 Generally, microwave absorption characteristics of a material,
Introduction
Organic-inorganic lead halide perovskites have attracted significant
attentions as promising semiconductors since their potentials have
been successfully implemented in lasers,1-2 photodetectors,3-5 X-ray
detectors,6-7 light-emitting diodes,8-10 hydrogen production,11-12 and
high-efficiency solar cells,13-15 etc. Particularly, MAPbX3 (MA =
which combine dielectric properties and magnetic properties, depend
on their intrinsic electromagnetic properties (i.e. electronic
conductivity, complex permittivity and permeability) as well as
extrinsic properties such as thickness and working frequency. The
traditional microwave absorbers such as ferrite, metallic particles,
carbon-based materials, and ceramics are still in use these days.25-26
Moreover, microwave absorber composites containing dielectric,
magnetic, or hybrid components, including organic-functionalized
inorganic BaTiO3 perovskites, have attracted extensive interests
because of their high permeability, high electric resistivity and high
resonance frequency.27-28 Although the microwave absorbing
mechanism of those materials is believed mainly based on either
dielectric loss or magnetic loss, these claims still lack the conclusive
support of related and available evidence to interpret microwave
absorption properties of organic-inorganic perovskite semiconductor
materials.
Here we directly probed the microwave absorbing properties of
MAPbI3, MAPbBr3 and MAPbCl3 perovskite crystals using
conventional transmission/reflection technique. Specifically, the
simulated reflection loss values for MAPbI3, MAPbBr3 and MAPbCl3
perovskites are -55.23, -54.70 and -46.44 dB, respectively, indicating
excellent microwave absorbability in the microwave range. Moreover,
long-term stability of the microwave absorption properties of
MAPbX3 perovskite crystals is also demonstrated. These findings
further emphasize the versatility and performance potential of
inorganic-organic lead halide perovskite materials for the
development of perovskite-based microwave devices.
+
CH3NH3 , X = I-, Br- or Cl-) perovskites can combine facile and low-
cost solution fabrication techniques with their favorable intrinsic
properties such as tunable direct optical band gap,16 high-absorption
coefficients,17 long carrier lifetime,18 and high carrier mobility19.
Similar to other traditional semiconductors, these unique physical
properties provide a view of the ultimate potential of MAPbX3
perovskites, and make high-quality MAPbX3 perovskite single
crystals much broader in optoelectronic applications than their thin
polycrystalline film counterparts.20-21 Currently, some detailed
fundamental and intrinsic properties of organic-inorganic perovskite
crystals are still under debate. Despite the stunning developments in
perovskite semiconductors performance, the microwave absorbing
properties of MAPbX3 perovskites have not yet been studied.
Microwave absorption materials can absorb microwave energy and
reduce electromagnetic backscatter effectively, by converting
electronic microwave energy into electric, thermal and magnetic
energy or dissipating electromagnetic wave by interference,22-23 have
become increasingly important in electronic equipment, not only for
a.State Key Laboratory of Electronic Thin Film and Integrated Devices, School of
Materials and Energy, University of Electronic Science and Technology of China,
Chengdu 610054, P. R. China. *Email: xbniu@uestc.edu.cn
b.Institute of Fundamental and Frontier Sciences, University of Electronic Science
and Technology of China, Chengdu 610054, P. R. China.
Electronic Supplementary Information (ESI) available. See DOI: 10.1039/x0xx00000x
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For measuring microwave absorption, these samples were prepared
Experimental
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with perovskite crystal powders loading DiOnI: p10a.r1a0f3f9in/C. 8TTCh0e06b8u3lKk
MAPbX3 single crystals samples were pulverized and mixed with
paraffin in a mass ratio of 3 : 1, and then pressed into a cylindrically
shaped compact with an inner diameter of 3.0 mm and an outer
diameter of 7.0 mm (Length: 5.0 mm). Next, the cylindric samples
were tightly sandwiched by two measured fixtures with the coaxial
inner and outer conductors attaching two electrodes. Then, the real (ε′
and μ′) and imaginary (ε″ and μ″) parts of the relative complex
permittivity and permeability of these samples were investigated
using a vector network analyzer (Agilent 8720ET) in the frequency
range of 0.5-18 GHz. Finally, we carried out microwave absorption
properties measurements with the transmission/reflection method, in
which the reflection loss (RL) were calculated using the relative
complex permittivity εr (εr = ε′ -jε″) and permeability μr (μr = μ′ - jμ″)
at a given frequency and thickness layer.
Materials
Lead iodide (PbI2, 99 %), lead bromide (PbBr2, 99 %), lead chloride
(PbCl2, 99 %) were purchased from Aladdin. Methylamine (CH3NH2,
33 wt.% in absolute ethanol), hydroiodic acid (HI, 57 wt.% in water),
hydrobromic acid (HBr, 48 wt.% in water) and hydrochloric acid
(HCl, 37 wt.% in water) were also obtained by Aladdin. Solvents
including anhydrous N, N-dimethylformamide (DMF, 99.8%),
anhydrous dimethyl sulfoxide (DMSO, 99.8%), gamma-
butyrolactone (GBL, anhydrous, 99%) were supplied by Sigma-
Aldrich. All the chemicals were used directly without any further
purification.
Synthesis of methylammonium halide (MAX)
+
Methylammonium halides (MAX, MA ) = CH3NH3 , X = I, Br, Cl)
were synthesized according to the previous report with
modifications.34 Typically, 34 mL methylamine and 38 mL HX (X =
I, Br, Cl) solution were mixed in a 150 mL three-necked flask at 0 oC
for 2 h in an ice-water bath. After that, the solvent was removed by
rotary evaporating at 50 °C for 1 h, the resulting white product was
washed with diethyl ether and then recrystallized from ethanol,
repeated three times, and finally dried at 60 oC overnight in a vacuum
oven. In the end, snow-white MAI, MABr, MACl crystals were
obtained.
Results and discussion
Grown of MAPbX3 perovskite single crystals
MAPbX3 (X = I, Br or Cl) single crystals were grown using a facile
evaporative crystallization growth (ECG) method with
modifications.29 The equimolar mixture of the prepared MAX and
PbX2 (X = I, Br or Cl) were dissolved under vigorous stirring in GBL,
DMF and DMSO at 60 oC, respectively. The corresponding solution
concentration was controlled at 1.2 M, 1.0 M and 2.0 M, respectively.
As-prepared perovskite precursor solutions were heated and kept on a
100 oC hotplate overnight. Black, orange and colorless small crystals
appeared as the heating time increases. To make the crystal larger,
small seed crystals were placed into the corresponding flesh
perovskite precursor solutions at 100 oC, and kept for 12 ~ 24 h until
larger crystals were grown. Subsequently, by using the larger crystals
as new seeds and repeating the above process, the crystals with even
larger size were obtained. Finally, bulk MAPbI3, MAPbBr3 and
MAPbCl3 single crystals were hot DMF to get rid of the leftover
solution form the surface and dried in a vacuum oven at 80 oC for 6 h.
Fig. 1 a) A schematic illustration of MAPbX3 (X = I, Br or Cl) single
crystal preparation. XRD patterns of MAPbX3 b) single crystals and
c) powders. The inset images show photographs of b) bulk large
MAPbX3 single crystals (crystal size ~ 10 mm) and c) MAPbX3 crystal
powders. d) Visible absorbance spectrum of MAPbX3 single crystals
and the inset images show photographs of small bulk MAPbX3 single
crystals (crystal size ~ 5 mm).
Structural characterizations
We synthesized high-quality bulk MAPbX3 (X = I, Br or Cl) single
crystals using a facile evaporative crystallization growth (ECG)
technique proposed by Liu and colleagues29, with modifications. As
depicted in Fig. 1a, we prepared perovskite precursor solutions by
mixing methylammonium halides (MAX, X = I, Br or Cl) with
corresponding lead halides (PbX2, X = I, Br or Cl) and solvents (GBL
for I, DMF for Br, DMSO for Cl, respectively) to form an unsaturated
solution on a 100 oC hotplate. Subsequently, the seal cap of
evaporation dish that control the evaporation rate of solvent played an
important role in the rate of single crystal growth. With the
evaporation of solvent, seed crystals (see Fig. S1a and S1b) appeared
when the solution was saturated or supersaturated. Next, seed
crystallites were added into flesh perovskite precursor solutions at 100
The as-prepared perovskite singles crystals and corresponding
powders were characterized by X-ray diffraction (XRD, Rigaku
RINT2400, Japan) with Cu Kα (λ = 0.1541 nm) radiation at 45 kV
and 40 mA. Thermal gravimetric analysis (TGA) was performed on a
TA Instruments Q50. The samples (10-15 mg) were heated from
ambient to 500 oC at a heating rate of 20 oC·min-1 under nitrogen flow
with a purge of 40 ml min-1. The optical images of MAPbI3 and
MAPbBr3 seed crystals were obtained on an Olympus BX51M optical
microscope. The Ultraviolet-Visible (UV-vis) absorption spectra were
recorded with TU-1810PC spectrophotometer in the wavelength
range of 300-800 nm in transmission mode.
Microwave absorption characterizations
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oC, and maintained for 12 ~ 24 h until larger crystals was grown. By measured relative complex permittivity and complex permeability
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DOI: 10.1039/C8TC00683K
using larger crystals as new seeds and repeating the above process, the data for the given absorber thickness and microwave frequency using
crystals (Seen in Fig. S1c and S1d) with appropriate sizes were the following equation:36
obtained. X-ray diffraction (XRD) patterns of MAPbX3 (X = I, Br or
Cl) single crystals demonstrate the pure perovskite phase for MAPbI3,
MAPbBr3, MAPbCl3 (Fig. 1b), confirming high quality of single
crystals2,30-31. The inset images show photographs of the MAPbI3,
MAPbBr3, MAPbCl3 single crystals with dimensions of ~14×13×2.2,
~11×11×2.0 and ~7×7×2.0 mm3. Meanwhile, the XRD
characterizations of MAPbX3 powders crushed from corresponding
single crystals were also performed in Fig. 1c. The corresponding
patterns show a set of strong diffraction peaks that can be assigned to
(
)
| |
RL dB = 20 log Γ =20 log |(Zin-Z0)/(Zin+Z0 )|
(1)
Where Γ is the reflection coefficient, Zin is the input characteristic
impedance of the absorber, which can be obtained from the following
expression:
Zin= Z0 (μ /ε ) tanh[ j(2πfd/c) μ ε ]
(2)
√
√
r
r
r
r
Where f is the frequency of the microwave in free space, c is the
velocity of light in vacuum, and d is the thickness of the absorber. εr
(εr = ε' - jε'') and μr (μr = μ' - jμ'') are the measured relative complex
permittivity and permeability, respectively. Z0 is the intrinsic
impedance of free space and given by the formula:
33
3
pure tetragonal MAPbI332, cubic MAPbBr3 and cubic MAPbCl3
crystal structures. Moreover, the visible absorbance spectrum of
bulk MAPbX3 single crystals were investigated. As shown in
Fig. 1d, it is clear that the light is absorbed strongly for bulk
MAPbX3 single crystals with the absorption onsets at ~ 860 nm, ~
600 nm and ~ 450 nm, respectively, which is in good matching with
the absorbance of three typical MAPbX3 perovskite crystals.20,29,34
The analyses on the absorption spectra of single crystals gave their
optical bandgaps of 1.45, 2.15 and 2.83 eV, respectively (Fig. S2a).
In addition, the thermal stability of bulk MAPbX3 single crystals
were investigated in Fig. S2b-S2d, which is similar to the
decomposition behaviour of classic high quality MAPbX3
perovskite single crystals.29
Z = μ /ε = 376.7 Ω
(3)
√
0
0
0
Fig. 2 a) Schematic drawing of the experimental set-up for
microwave absorption measurement for MAPbX3 (X = I, Br or Cl)
crystal samples. Schematics of the b) cross-section and c) top view
of the measured sample. d) Photographs of the measured MAPbX3
crystal samples.
Fig. 3 3D color plots of numerical simulated reflection loss versus
thickness as a function of frequency: a) MAPbI3, b) MAPbBr3, c)
MAPbCl3 and d) paraffin samples. e) Microwave absorption curves
of the best performed MAPbX3 crystal samples with optimal
thicknesses. f) Microwave absorption curves of MAPbBr3 crystal
samples versus thickness.
Fig. 2a schematically depicts the experimental set-up for the
microwave characteristic measurements. The transmission/reflection Table 1 The optimal microwave absorption parameters of these
method 35 was carried out by using a vector network analyzer in the measured samples.
frequency range of 0.5-18 GHz. The device can show reflected and
Frequency
(GHz)
16.77
15.46
13.54
18.00
18.00
18.00
15.99
18.00
18.00
16.6
Thickness
(mm)
1.62
Reflection loss
(dB)
Samples
transmitted transient responses when an incident wave pulse is
radiated by a free space transmission path to the toroidal samples (Fig.
S3). The sample was tightly sandwiched by two electrodes with the
coaxial inner and outer conductors, and schematics of the cross-
section and top view of the measured specimen fixture are shown in
Fig. 2b and 2c. The powder crystal circular rings were fabricated by
mixing MAPbX3 crystals and paraffin as illustrated in Fig. 2d (See the
experimental section). Here, we simulated the reflection loss (RL) of
the as-prepared MAPbX3 (X = I, Br or Cl) samples using the
transmit line theory of electromagnetism absorption, which was
demonstrated to be an effective model for a single-layer plane-wave
absorber. In this model, the RL value can be calculated from the
MAPbI3
MAPbBr3
MAPbCl3
PbI2
PbBr2
PbCl2
MAI
MABr
MACl
-55.23
-54.70
-46.44
-4.58
-6.87
-12.73
-3.13
-3.00
-2.762
-2.945
1.76
1.95
2.03
1.82
1.69
2.60
2.24
2.34
Paraffin
3.54
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The 3D presentations of the calculated theoretical RL data of the special structural characteristics result in the electromagnetic wave
View Article Online
DOI: 10.1039/C8TC00683K
MAPbX3 (X = I, Br or Cl) samples with varying frequencies and absorptions of the organic-inorganic MAPbX3 perovskite crystals.
thicknesses are exhibited in Fig. 3a-3c. Compared with the pure
In order to investigate the microwave absorption mechanism of
paraffin wax sample (Fig. 3d), all the MAPbX3 samples exhibit the perovskite samples, we independently measured the complex
excellent microwave absorptions in two thickness ranges of 1.0- relative permittivity and permeability of MAPbX3 crystal samples.
2.5 mm and 4.0-7.0 mm at high frequency of 12-18 GHz (Ku- Fig. 4a shows the frequency dependence of the real (ε') and imaginary
band frequency). The optimal microwave absorbing parameters are (ε") parts of the relative complex permittivity (εr = ε' - jε") of MAPbX3
summarized in Table 1. On the basis of the optimal thickness in the (X = I, Br or Cl) crystal samples. It can be seen that the ε' values
classical range of 1-5 mm, the minimum RL peak values of the of the three MAPbI3, MAPbBr3 and MAPbCl3 crystal samples
MAPbI3, MAPbBr3 and MAPbCl3 samples are -55.23, -54.70 and - decrease with the increase of frequency and exhibit their minimum
46.44 dB at 16.77, 15.46 and 13.46 GHz with a thickness of 1.62, 1.76 values of 6.1, 6.0 and 6.5 with respect to the frequency of 16.9, 16.7
and 1.95 mm, respectively (Fig. 3e). It is clearly seen that the and 15.9 GHz, respectively. It is concluded that the distinct dielectric
optimal peak intensity gradually increase from Cl to Br and I, and the response characteristic is demonstrated as dielectric dispersion.38-39
peaks move to the high frequency region with the decreasing Moreover, the MAPbI3, MAPbBr3 and MAPbCl3 crystal samples
thickness. Additionally, the optimization of thickness for the demonstrate relatively low ε′′ values with the maxima of 1.4, 2.8
MAPbBr3 sample is also demonstrated in Fig. 3f. There is one narrow and 4.4 at 17.8, 17.3 and 15.5 GHz, respectively, suggesting the
and strong microwave absorbing peak as the thickness increases. occurrence of strong resonance. For comparison, the ε′′ values of
Obviously, the thickness of the sample is one of the crucial parameters PbX2 and MAX (X = I, Br and Cl) samples maintain almost constant
that affect the intensity and location of the frequency with RL 0 (see Fig. S5 and S6). According to the free-electron theory,40 the
minimum.37 On the basis of these results, it can be found that all the ε′′ value can be summarized as the following equation:
σ
organic-inorganic MAPbX3 crystal samples exhibit excellent
microwave absorption properties with appropriate thickness at high
frequency.
ε''= 2ε πf
(4)
0
Where σ represents electric conductivity, f is the frequency of
the microwave in free space, and ε0 is the permittivity of free space
ε0 = 8.854 × 10-12 F m-1). It is confirm that the low ε′′ means low
(
conductivity and causes low electric polarization. This is because
organic-inorganic lead halide perovskite is a typical semiconductor
material with direct bandgap. However, it is well known that
MAPbX3 perovskites have very high carrier mobility,41 which may
result in electron polarization with strong dielectric loss.
Furthermore, the plotting of ε′′ versus ε′ is shown in Fig. 5. As for
MAPbX3 samples, one or two Cole-Cole semicircles are clearly
observed and distorted, which is consistent with Debye dipolar
relaxation model and indicate the occurrence of dielectric relaxation
process.42 This also suggests that the permittivity at microwave
frequency can be contributed by dipole relaxation
polarization.39,43-44
Fig. 4 a) Complex permittivity (ε' and ε"), b) complex permeability
(μ' and μ"), c) dielectric loss/magnetic loss and d) Co (Co = μ"(μ')-2f-1)
curves of MAPbX3 (X = I, Br or Cl) crystal samples.
To evaluate the microwave absorption performance of the
perovskite samples, the lead salts (PbI2, PbBr2 and PbCl2) and organic
halides (MAI, MABr and MACl) as the raw material of the
perovskites display very low RL values at low thickness (See in Table
1). It is interesting that both PbBr2 and PbCl2 samples show excellent
microwave absorption only with large thickness (> 5.0 mm) at high-
frequency regime (Fig. S4 and Table S1, Supporting Information),
which is useful to improve microwave absorptivity of MAPbX3
perovskites with large thickness. However, it is the fact that PbI2
sample shows relative low microwave absorption in the whole
thickness range. Moreover, the MAI, MABr and MACl powder
samples exhibit hardly any microwave absorption at the whole range
of frequency. Thereby, there might be a possible reason that the
Fig. 5 The real part (ε') versus imaginary (ε") plots of complex
permittivity of MAPbX3 (X = I, Br or Cl) crystal samples.
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2πμ0σd2
3
C0=μ''(μ')-2f-1=
(5)
View Article Online
DOI: 10.1039/C8TC00683K
Where μ0 is the permeability of free space and σ represents
electric conductivity. If the magnetic loss from eddy-current loss,
the C0 values should be constants when the frequency varies.
However, the values of C0 have two strong resonance peaks as a
function of frequency (Fig. 4d). Thus, it can be concluded that the
magnetic loss for MAPbX3 perovskites is mainly ascribed to the
natural resonance, which makes the behaviors of dielectric and
magnetic losses more complex.
In spite of the excellent microwave absorption capabilities, one
major concern is the poor stability as for organic-inorganic lead halide
perovskites, which is a barrier to practical applications. We therefore
monitored the long-term stability in microwave absorption of these
perovskite samples. The MAPbX3 crystal samples were tested without
o
encapsulation and exposed directly to the environment at 25 C with
30-50 % humidity. Fig. 6a presents the optimal RL values of the
MAPbX3 crystal samples as a function of storage time in nitrogen
atmosphere. In terms of the RL data of the perovskite samples, the
microwave absorptivity remains 80 % up to 30 days, while the RL
values are degraded to almost 50 % after 180 days. Such exceptional
stability can be attributed to the robustness introduced by paraffin,
which forms compact and stable circular rings, again as a consequence
of the inhomogeneous degradation of different perovskite/paraffin
composites. In particular, as for MAPbBr3 crystal samples, the
degradation of microwave absorption versus frequency and thickness,
is displayed in Fig. 6 b. Notably, the microwave absorption ability
gradually decreases as the storage time increases in small
thickness ranges of 1.0-2.5 mm, while increases as the storage
time increases in large thickness ranges of 4.0-7.0 mm. It is
clearly revealed that the degradation of the microwave absorption
is likely due to decomposition of the MAPbBr3 perovskite along with
the increasing of PbBr2 component. To obtain more in-depth
understanding of the mechanism behind the observed degradation in
the microwave absorption, XRD measurements of the surface of
MAPbX3 crystal samples (Photographs in Fig. S7) were carried out in
Fig. 6c-6e. As depicted in Fig. 6c, it is clear the MAPbI3 perovskite-
related peaks at scattering angles 2θ = 14.3o (110), 28.6 o (220) and
Fig. 6 a) The long-term stability of microwave absorption properties
of MAPbX3 (X = I, Br or Cl) crystal samples. b) 2D color plots of
numerical simulated reflection loss of MAPbBr3 crystal samples
versus thickness and frequency as a function of time. XRD patterns
of c) MAPbI3, d) MAPbBr3 and e) MAPbCl3 crystal samples were
measured as function time stored in N2. f) The proposed microwave
absorbing degradation mechanism of the MAPbX3 crystal samples.
The real (μ') and imaginary (μ") parts of the relative complex
permeability μr (μr = μ' - jμ") versus frequency for MAPbX3 (X = I,
Br or Cl) crystal samples are shown in Fig. 4b, which represent
the storage and loss capability of magnetic energy, respectively
.
Obviously, the μ' and μ" of MAPbX3 samples almost maintained
constant (1 and 0, respectively), exhibiting no magnetic loss in the
0.5-12 GHz frequency range. However, the μ' of MAPbI3, MAPbBr3
and MAPbCl3 crystal samples demonstrates a slight increase and the
values of μ' are 1.4, 1.3 and 1.5 at frequency 16.9, 16.6 and 15.9 GHz,
respectively. Similarly, the corresponding μ" values are 0.4, 0.5 and
0.3 with corresponding frequency at 17.7, 17.3 and 15.6 GHz,
respectively. It suggests that magnetic loss still happens despite
of the absence of non-magnetic properties in these perovskites. After
that, we calculated the dielectric loss (tan δε = ε"/ε') and magnetic loss
(tan δμ = μ"/μ') as dissipation factors (Fig. 4c). As illustrated in Fig.
4c, the tan δε of all the MAPbX3 samples exhibit two resonance peaks
around 14-18 GHz, indicating the perovskites exhibit intense
dielectric losses. It is further confirmed that the loss mechanisms are
attributed to dominant dipolar polarization and associated relaxation
phenomena.25 Meanwhile, the tan δµ also demonstrates similar
characteristics with that of the µ′′, implying that the loss mechanism
of the perovskites includes magnetic loss. Generally, the microwave
magnetic loss of magnetic materials mainly results from magnetic
hysteresis, domain-wall displacement, natural resonance and eddy
current loss.45 It is well known that the C0 value can be summarized
as the following equation:
o
43.2 (330) have disappeared after stored in N2 for 180 days.
However, the intensity of the peaks of MAPbBr3 and MAPbCl3
samples show a small reduction (Fig. 6d and 6e), strongly suggesting
the less degradation of the perovskites. Interestingly, for three
perovskite samples, there is no peak at 12.5o, corresponding to the
absence of PbI2. The finding points to no transformation from
MAPbX3 to PbX2 without loss of MAX, again suggests that the
encapsulation of the paraffin on the perovskite is of the utmost
importance to protect the decomposition of the perovskites. From our
results, there may be another reason that the electromagnetic waves
can be effectively absorbed by the perovskites and converted into
thermal energy, which caused by the intrinsic instability of the
organic-inorganic perovskites (Fig. 6f).
Conclusions
In summary, for the first time, we have investigated the
microwave absorption performance of MAPbI3, MAPbBr3, and
MAPbCl3 perovskite crystal powders using the transmit line
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theory of electromagnetism absorption. With the simulation of
reflection loss, we have discovered the extremely excellent 12 M. Crespo-Quesada, L. M. Pazos-OuDtoOnI,: 10J..10W39a/rCn8aTnC, 0M06.83FK.
microwave absorbability in these perovskites. More importantly, Kuehnel, R. H. Friend, E. Reisner, Nat. Commun., 2016, 7, 12555.
the mechanism of the microwave absorption properties has been 13 S. S. Shin, E. J. Yeom, W. S. Yang, S. Hur, M. G. Kim, J. Im, J. W.
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View Article Online
electromagnetic match in perovskite structure, the lags of
polarization and strong natural resonance. Finally, we also note
that the long-term stability of microwave absorbability
R. Quintero-Bermudez, M. J. Yuan, B. Zhang, Y. C. Zhao, F. J.
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Conflicts of interest
17 H. S. Kim, C. R. Lee, J. H. Im, K. B. Lee, T. Moehl, A. Marchioro,
There are no conflicts to declare.
S. J. Moon, R. Humphry-Baker, J. H. Yum, J. E. Moser, M. Gratzel,
N. G. Park, Sci. Rep., 2012, 2, 591.
18 C. Wehrenfennig, G. E. Eperon, M. B. Johnston, H. J. Snaith, L.
M. Herz, Adv. Mater., 2014, 26, 1584-1589.
19 G. Xing, N. Mathews, S. Sun, S. S. Lim, Y. M. Lam, M. Gratzel,
S. Mhaisalkar, T. C. Sum, Science, 2013, 342, 344-347.
20 M. I. Saidaminov, A. L. Abdelhady, B. Murali, E. Alarousu, V. M.
Burlakov, W. Peng, I. Dursun, L. Wang, Y. He, G. Maculan, A.
Acknowledgements
The authors acknowledge the financial support from the
Recruitment Program of Global Young Experts of China and
Sichuan one thousand Talents Plan.
Goriely, T. Wu, O. F. Mohammed, O. M. Bakr, Nat. Commun.,
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Journal of Materials Chemistry C
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DOI: 10.1039/C8TC00683K
Graphical Abstracts:
Organic-inorganic CH3NH3PbI3, CH3NH3PbBr3 and CH3NH3PbCl3 perovskites
possess outstanding microwave absorbability with high reflect loss values.