Stacking of Layered Halide Perovskite from Incorporating a Diammonium Cation into Three-Dimensional Perovskites

Article abstract of DOI:10.1021/acs.langmuir.9b02524

Quasi two-dimensional (2D) layered perovskites have been emerging as promising candidates for photovoltaic cells because they exhibit intrinsic stability and a higher tunability of optical properties compared to three-dimensional (3D) perovskites. However, since most 2D perovskites have bulkier groups as an organic space group, they will inevitably have a van der Waals gap between the inorganic layers and their crystal growth directions orient in a lateral direction. It also interrupts carrier transport across the conducting inorganic layer in the solar cell. Here, we presents the new homologous 2D layered perovskites, (HA)(A)_n-1Pb_nI_3n+1, where HA stands for the histammonium ((C₅N₃H₁₁)²⁺) as a diammonium cation and A stands for methylammonium (CH₃NH₃ ⁺) or formammonium (HC(NH₂)₂ ⁺). Since the ditopic HA has a diammoinium cation, it connects the inorganic slabs stacked in the vertical direction. The inorganic layer is stacked on the other layer to form a layered structure, which results in rigid and stable structures. These materials (1.64 eV for (HA)(FA)_n-1Pb_nI_3n+1 and 1.80 eV for (HA)(MA)_n-1Pb_nI_3n+1) have significantly lower band gaps than those of HAPbI₄ (2.20 eV). Compared to the pure 2D and 3D perovskites, these perovskites have a longer electron lifetime due to the vertical crystal structure and show improved environmental stability for perovskite solar cell application.

Full text of DOI:10.1021/acs.langmuir.9b02524

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Interfaces: Adsorption, Reactions, Films, Forces, Measurement Techniques, Charge
Transfer, Electrochemistry, Electrocatalysis, Energy Production and Storage
Stacking of Layered Halide Perovskite from Incorporating
a Diammonium Cation into Three-Dimensional Perovskites
Mi-Hee Jung
Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.9b02524 • Publication Date (Web): 20 Nov 2019
Downloaded from pubs.acs.org on November 25, 2019
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Stacking of Layered Halide Perovskite from Incorporating a
Diammonium Cation into Three-Dimensional Perovskites
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Mi-Hee Jung* †
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
Department of Nanotechnology and Advanced Materials Engineering, Sejong University, 209,
Neungdong-ro, Gwangjin-gu, Seoul 05006, Republic of Korea; Fax: +82-2-3408-4342; Tel: +82-2-6935-
2
443; E-mail: mhjung@sejong.ac.kr
Abstract
Quasi two-dimensional (2D) layered perovskites have been emerging as promising candidates for a
photovoltaic cell because they exhibit intrinsic stability and a higher tunability of optical properties
compared to three-dimensional (3D) perovskites. However, since most 2D perovskites have bulkier groups
as an organic space group, it will inevitably have a van der Waals gap between the inorganic layers, and
their crystal growth directions orientate in a lateral direction. It also interrupts carrier transport across the
conducting inorganic layer in the solar cell. Here, we presents the new homologous 2D layered perovskites,
(
HA)(A)n1Pb
n
I
3n1, where HA stands for the histammonium ((C
5
N
3
H
11)2+) as a diammonium cation, and A
+). Since the ditopic HA have
stands for methylammonium (CH NH
3
3
+) or formammonium (HC(NH
)
2 2
diammoinium cation, it connects the inorganic slabs stacked in the vertical direction. The inorganic layer
is stacked on the other layer to form a layered structure, which results in rigid and stable structures. These
materials (1.64 eV for (HA)(FA)n1Pb
n
I
3n1 and 1.80 eV for (HA)(MA)n1Pb I3n1) have significantly lower
n
band gaps than the HAPbI (2.20 eV). Compared to the pure 2D and 3D perovskites, these perovskite have
4
a longer electron lifetime due to the vertical crystal structure and show improved environmental stability
for the perovskite solar cell application
Keywords histamine, bication, formamidinium, methylammonium, perovskite, lead iodide, solar cell
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■ INTRODUCTION
Organic-inorganic hybrid perovskites (OHP) and three-dimensional (3D) perovskites have received great
attention for their ability to boost solar cell efficiency dramatically. The desirable properties, such as the
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high optical absorption coefficient ( = 10 ~ 10 cm for hv > 1.7 eV), the long electron and hole diffusion
length ( > 1 m for MAPbI3-xCl (MA = CH NH ) and > 175 m for single crystal MAPbI
),2-3 and low
x
3
3
3
4
exciton binding energy (50 meV) have enabled converting sunlight directly into electric power to increase
above 22% in a few years, which has rendered competitors development to the current commercial
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-6
technologies. However, 3D perovskites (i.e. CH
3
NH
3
PbI
3
or CH
3
NH
3
SnI ) is very sensitive with ambient
3
conditions, especially with moisture and oxygen, which is the main cause that decomposes the perovskite
crystal structure in the air and limit real application of the prototype 3D halide perovskite materials.
Alternately, with robust chemical stability and an excellent optoelectronic property, two-dimensional (2D)
perovskites are evolving into an important class of high performance semiconductors. The general formula
2
+
2+
2+
for 2D materials is A′
2
A
n–1
M
n
X
3n+1 or A′An–1
M X3n+1 (A′ = 1+ or 2+, A = 1+ cation, M = Pb , Sn , Ge ,
n
2+
2+
–
–
– 7
Cu , Cd , etc., X = Cl , Br , and I ), which are formed by the slicing of a 3D perovskite along (100),
(110), (111) cyrstallographic planes with the elimination of the octahedra layer in the slicing plane. Among
them, the higher number of layers (n  2) have been explored as potential candidate materials of pure 2D
or 3D perovskites for the high performance and long term stability of perovskite solar cells: (BA)
3n+1 (BA = butylammonium, and n = 1 ~ 4),8-10 (PEA)
Pb 3n+1 (PEA is phenylethylammonium
and n = 2, 3),11-12 (C(NH 3n+1 (n = 1, 2, 3),13 A′(MA)n–1Pb
I3n+1 (A′ = 3-
2
(MA)n-
1
n
I
2
(MA)n-1Pb I
n
2
)
3
)(MA)
n
Pb
n
I
n
7
(
aminomethyl)piperidinium or 4-(aminomethyl)piperidinium) and n = 1 ~ 4). However, the crystal
structure of these layered perovskites still have plate types that remain, even though the 2D perovskite was
incorporated by introducing MA cation in the crystal structure. The introduction of the 3D structure into
the 2D structure was made to increase the thickness of the inorganic layer and grow vertically, but the
layered 2D perovskite was propagated to two directions (the ac plane) by being present in the crystal
structure. Therefore, the introduction of the 2D structure to complement the 3D structure is still insufficient
for effective charge transport.
Herein, we reports on (HA)(FA)n-1Pb
n
I
3n+1 (HA = C
3
N
2
H
4
CH
2
CH
2
NH
3
, FA = HC(NH
2
2
) ) and
(
HA)(MA)n-1Pb NH ), that feature vertical layered 2D halide perovskites. This is due to
n
I
3n+1 (MA = CH
3
3
the bication bridging the inorganic layers in the interlayer space. We choses small molecules of HA, which
is a divalent cation and act as a double linker and connects the inorganic layers closely. This results in the
stacking of inorganic layers vertically. HA is also soluble in a wide range of solvents. To make the vertical
layered 2D perovskite, We used formamidinium lead iodide (FAPbI ) and methylammonium lead iodide
3
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(
MAPbI
band gap (1.48 eV) compared to MAPbI
which is very favorable for a solar cell.14-22 However, FAPbI
to the partial decomposition of FAPbI to PbI . In addition, it undergoes phase transition from a black
, space group P3m1), which is formed at a higher temperature (~ 160
, space group P6
mc),23-28 which is
3
) as a 3D perovskite. FAPbI
3
has recently emerged as a potential candidate material due to its low
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(1.57 eV) and an absorption band up to the near infrared region,
is an unstable structure in the atmosphere due
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trigonal perovskite phase (-FAPbI
3
o
C) than the yellow hexagonal non-perovskite phase (-FAPbI
3
3
undesirable for the photoelectric conversion in a solar cell. However, HA was incorporated into -FAPbI
3
3
to create a mixed-cation perovskite that exhibit significantly improved stability compared with -FAPbI
and importantly, they formed a vertical layered (HA)(FA)n-1Pb
groups. Strikingly, these structures show the long carrier lifetime, which is approximately 10 times as that
of a -FAPbI perovskite. When (HA)(FA)n-1Pb 3n+1 perovskites were applied to planar solar cells, the
n
I3n+1 perovskite due to HA bifunctional
3
n
I
resulting devices exhibit a high power conversion efficiency of 6.75% with moisture stability. We believes
that this approach will help guide for further improvement in the performance of related perovskite
materials.
■
EXPERIMENTAL SECTION
Starting Materials. The lead oxide (PbO, 99%), histamine (C
HI, 57 wt. % in H O), hypophosphorous acid (H PO , 50 wt. % in H
anhydrous, 99.8%), dimethyl sulfoxide (DMSO, anhydrous, ≥ 99.9%), methylamine hydrochloride
CH NH Cl, ≥ 98%), histamine dihydrochloride (C ·2HCl, ≥ 99%) and chlorobenzene (CB,
anhydrous, 99.8%) were purchased from Sigma-Aldrich and were used without further purification. The
spiro-MeOTAD was purchased from Luminescence Technology Corporation. The CH NH I (MAI) was
synthesized by neutralizing equimolar amounts of a 57% w/w aqueous HI and 40% w/w aqueous
methylamine (CH NH ). The white precipitate was collected by evaporating the solvent using rotary
evaporation at 60 °C under reduced pressure.
Synthesis of HAPbI . A 100 mL two-necked round-bottom flask was charged with 5.0 mL of stabilized HI
57% aqueous solution) and a trace amount of hypophosphorous acid (1.5% H PO ). The mixture was
degassed with nitrogen for 1 min, and the flask was kept under nitrogen for the duration of the experiment.
The flask was heated in an oil bath to 120 °C, and PbI (0.46101 g, 1 mmol) was added and then stirred
3
N
2
H
3
CH
2
CH
2
NH
2
,  97%), hydriodic acid
(
2
3
2
2
O), N,N-dimethylformamide (DMF,
(
3
3
5
H N
9 3
3
3
3
2
4
(
3
2
2
vigorously until the solid had dissolved completely. Histamine dihydrochloride (0.18407 g, 1 mmol) was
then added to the flask, which immediately resulted in an orange colored precipitate (Figure S1). The
solution was stirred for an additional 15 min. Then, the heat was removed, and the flask was allowed to air-
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cool while being stirred gently. The solution and precipitate were washed with anhydrous ether and
centrifuged three times. The product was dried at 50 °C for 24 h in a vacuum oven.
Synthesis of (HA)(FA)n-1Pb
stabilized hydriodic acid (HI, 57 wt. % in H
O). The mixture was degassed with nitrogen for 1 min, and the flask was kept under nitrogen for the
n
I
3n+1. A 100 mL two-necked round-bottom flask was charged with 5.0 mL of
2
O) and 1 mL of of hypophosphorous acid (H PO , 50 wt. % in
3
2
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duration of the experiment. The flask was heated in an oil bath to 120 °C and PbO (0.6696 g, 3 mmol) was
added. Then, it was stirred vigorously, and it formed a bright yellow solution. Subsequently, solid FAI
(
0.3439 g, 2 mmol) was then added into the hot PbI solution. When a black precipitate initially began to
2
form, the solution was rapidly re-dissolved under vigorous stirring to obtain a bright clear yellow solution.
In a separate beaker, the histamine dihydrochloride (0.1012 g, 0.55 mmol) was neutralized with HI 57
wt%/H
2
O (2 mL, 15 mmol) in an ice bath. The HAI
2
solution was slowly added drop by drop into the PbI
2
solution while being stirred continuously. A black precipitate was initially formed, which was re-dissolved
while heating the combined solution to a boil. The stirring was then discontinued, and the hot solution was
slowly cooled to room temperature. During this time, cherry red rectangular-shaped plates started to
precipitate (Figure S1). After the solution was allowed to stand for 3h, the crystal was separated with suction
o
filtration, washed with diethyl ether, and dried in a vacuum oven at 60 C. A yield of 62% was estimated
relative to the total Pb content.
Synthesis of (HA)(MA)n-1Pb
Pb 3n+1. However, the amount of MACl was increased as the MAPbI
compared to the -FAPbI (Figure S1). The experimental ratio for HAI: MAI: PbO was 0.55: 3:3. The yield
based on total Pb content is 56%.
Perovskite Film Preparation. To confirm the orientation of the perovskite film, the 1M Pb precursor
n
I
3n+1. A similar synthetic procedure was used to synthesize the (HA)
2
(MA)n-
1
n
I
3
precipitated relatively slowly
3
2
+
solution of (HA)(FA)n1Pb
n
I
3n1 (n = 2, 3 and 4) and (HA)(MA)n1Pb
n
I
3n1 (n = 2, 3 and 4) were prepared
by dissolving the corresponding amount of HAI
2
, MAI, FAI and PbI
2
in anhydrous dimethyl formamide
and dimethyl sulfoxide (4:1 v:v) solution. The perovskite solution was spin coated on the glass substrate at
o
4
000 rpm for 30 s. The substrates were annealed at 100 C for 30 min.
Single crystal X-ray diffraction. The single crystal X-ray diffraction data was measured with synchrotron
radiation ( = 0.61000 Å) on a ADSC Quantum-210 detector at BL2D SMC with a silicon (111) double
crystal monochromator (DCM) at the Pohang Accelerator Laboratory, Korea. The PAL BL2D-SMDC
program 29 was used for data collection (detector distance is 63mm, omega scan; ∆ω = 3º, exposure time is
1
sec per frame), and HKL3000sm (Ver. 703r) 30 was used for cell refinement, reduction, and absorption
correction. The crystal structure of perovskites was solved by the direct method with the SHELXT-2014
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program 31 and refined by full-matrix least-squares calculations with the SHELXL-2014 program package.
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Steady-state and Time-resolved photoluminescence (TRPL). The steady-state PL spectra were
measured by dividing and guiding the PL signal through an optical fiber using a HORIBA LabRAM HR
Evolution confocal RAMAN microscope. A 532 nm laser (0.01% power) was used to excite all samples at
50× magnification. A time-resolved PL (TRPL) study was performed using an inverted-type scanning
confocal microscope (MicroTime-200, Picoquant, Germany) with a 60 × (air) objective. The lifetime
measurements were performed at the Korea Basic Science Institute (KBSI), Daegu Center, Korea. Asingle-
mode pulsed diode laser (470 nm with a pulse width of ~30 ps) was used as an excitation source. A dichroic
mirror (490 DCXR, AHF), a long-pass filter (HQ500lp, AHF), a 75 μm pinhole, and a single photon
avalanche diode (PDM series, MPD) were used to collect emissions from the samples. The time-correlated
single-photon counting (TCSPC) technique was used to count fluorescence photons. The TRPL images
consisted of 200×200 pixels were recorded using the time-tagged time-resolved (TTTR) data acquisition
method. Exponential fittings for the obtained PL decays were performed using Symphotime-64 software
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Ver. 2.2) with the exponential decay model: Iꢀtꢁ ꢂꢃ∑ ꢄ ꢆꢇꢈ⁄ꢉꢊ , where I(t) is the time-dependent PL
ꢅ
(
intensity, A is the amplitude, and τ is the PL lifetime.
Ultraviolet photoelectron spectroscopy (UPS). The UPS measurements were carried out using an
AXIS ultra-delay line detector (DLD) (Kratos inc.) in the Korea Basic Science Institute, Daejeon, and the
He I (21.22 eV) emission line was employed as a UV source.
Optical absorption spectroscopy. The optical diffuse reflectance spectra was measured using the Agilent
(Cary-5000) UV-VIS-NIR system. Polytetrafluoroethylene was used as the non-absorbing reference
material of 100% reflectance. The reflectance versus wavelength was converted to the absorption data to
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−1
calculate the band gap (E ) using the Kubelka−Munk equation : α/S = (1 − R) (2R) , where R is the
g
reflectance and α and S are the absorption and scattering coefficients, respectively.
Powder X-ray diffraction (XRD). Power XRD patterns were measured using an Empyrean PANalytical
instrument with Cu Kα radiation (40 kV, 30 mA, λ = 1.54056 Å) and a Ni filter with a graphite
monochromator.
Ellipsometry. Spectroscopic ellipsometry was performed using a J.A.Woollam M2000D ellipsometer. The
wavelength range measured was 381-893 nm at three different incident angles: 55°, 65° and 75°. Final fits
to the data using the general oscillator functions were carried out for all the angles simultaneously with
J.A.Woollam’s CompleteEase software.
Atomic force microcopy (AFM). AFM measurements were carried out on a Multimode XE-150
instrument (PSIA Inc.) operating in noncontact mode with silicon cantilevers (resonance frequency in a
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range of 204-259 kHz, an integrated Si tip with a typical radius of 10 nm curvature).
Solar cell fabrication and device performance measurement. The N type TiO
2
layer formation was used
with the following method. A 50 nm compact layer of TiO was deposited on the FTO substrate by spin
2
coating (2000 rpm 30s) a mildly acidic solution of titanium isopropoxide (TTIP) in ethanol containing (350
o
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L TTIP in 5 mL EtOH with 0.013 M HCl). Then, the sintering process was conducted at 550 C for 30
min. A mesoporous TiO
2
layer was spin-coated on the TiO
2
compact layer with diluted TiO paste
2
(
DYESOL-30NRD) with ethanol in a ratio of 1:3.5 w/w at 500 rpm for 5 s, 3,000 rpm for 10 s, and 6,000
o
rpm for 30 s. The substrate was further treated with a 20 mM TiCl aqueous solution at 70 C for 30 min,
4
o
rinsed with deionized water and ethanol, and then sintered at 500 C for 30 min. The 30 wt% perovskites
were dissolved in mixed solvent (DMF:DMSO = 4:1). The solution was spin coated on the N type TiO
2
o
layer at 4,000 rpm for 30s followed by the annealing process at 100 C for 30 min. A solution for the spiro-
MeOTAD coating was prepared by dissolving 72.3 mg of spiro-MeOTAD in 1 mL of chlorobenzene and
adding 28.8 μL of 4-tert- butyl pyridine and 17.5 μL of lithium bis(trifl uoromethanesulfonyl) imide
3
4
solution (520 mg Li-TSFI in 1 mL acetonitrile (Sigma–Aldrich, 99.8%)). The spiro-MeOTAD was
deposited at 4,000 rpm for 30s on the perovskite layer. All processes were conducted in ambient air. The
gold layer of 800 Å for the counter electrode was deposited on the perovskite layer with the thermal
evaporation at 1.5 Å/s.
The photocurrent (Jsc) and photovoltage (Voc) of the solar cells were measured with an active area of
2
0
.175 cm using Keithley 2400 source meter and a Newport solar simulator (model 91192), which offered
simulated solar light at AM 1.5, calibrated with a NIST-certified monocrystalline Si solar cell (Newport
532 ISO1599). Incident photon to current efficiency (IPCE) was measured using an IQE200B designed by
the Newport Corporation. A 100 W Xenon lamp was applied as the light source for the monochromatic
beam. For its calibration of monochromatic light intensity, a reference silicon photodiode (NIST-calibrated
photodiode G425) was used.
■
RESULTS AND DISCUSSION
The 2D (HA)(FA)n1Pb
the PbO, HAI and FAI. The neutralized HAI in the HI solution was added into the homogeneous solution
of the I -free concentrated containing stoichiometric PbO and FAI. The clear yellow solution was initially
n
I3n1 family compounds were prepared using the stoichiometric reaction between
2
formed under vigorous stirring at the boiling temperature, which upon cooling to room temperature black
precipitate was obtained in the form of a 3D rectangular stacking shape. Figure 1 shows the crystal structure
of HAPbI
4
and 2D (HA)(FA)n1Pb
n
I
3n1, and crystallographic data are listed in Table 1. The HAPbI
4
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crystallizes in the monoclinic space group P2 /n with lattice parameters a = 8.8902(18) Å, b = 20.038(4) Å,
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1
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2
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2
2
2
2
2
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c = 9.0050(18) Å, α = 90°, β = 91.86(3)°, and γ = 90°. It is the layered perovskite template by the divalent
2
+
organic cation histammonium, (C
The HA dications layer formed a double layer between the corner-sharing octahedral of the [PbI
which resulted in the inorganic layer being closer. Since the interlayer terminal iodideiodide distance is
.38 Å (Figure 1a), it can be regarded as providing a vertical layered structure by deviating from the general
trend of the plate form when a 2D perovskite is combined with a 3D perovskite. We will explain the
formation of vertical layered structure when the HAPbI was combined with the -FAPbI or MAPbI later.
5
N
3
H11) that contains both primary ammonium and imidazolim cations.
2

6
] layer,
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
4
4
3
3
The MIM bond angle in these hybrid layered perovskite materials is another important feature, since the
35
bonding interactions reflected by the bond angle have the greatest impact on the band gaps. The bond
o
o
angles of PbIPb in HAPbI were 156.17 and 178.05 . The deviation of PbIPb from the ideal
4
o
o
o 36
(undistorted) value of 180 was smaller than that of similar compounds, HAPbBr
4
(174.84 and 153.66 )
o
o
o
o 37-38
and (C
6
H
5
C
2
H
4
NH
3
)
2
PbCl (151.45 , 151.37 , 153.21 and 153.28 ).
4
This can be attributed to the
difference of strength of the H-bonding due to the special structure of the organic dications. The local
environment of the organic ammonium groups, which are shown in Figure 1a consists of four hydrogen
bonds per histamine unit, formed between the protonated amine and are adjacent to four iodide ions on the
2

39
inorganic [PbI ] layer. Considering bond distances H2I1 and H3I1 : 2.65 Å and 2.78 Å between
6
the NH on the imidazole group and the apical iodide, respectively. 3.01 Å and 2.83 Å between the other
amine group and the adjacent iodide ions (H1AI2 and H1BI4, respectively) these hydrogen bonding
interactions are weak. Since the imidazole group in the histamine unit has steric hindrance for the hydrogen
3
6
bond with inorganic sheets, the electrostatically interactions more dominantly occur between the charged
organic cations and the inorganic layers.40
To make the vertical layered structure, we introduced the 2D HAPbI
structure. FAPbI has two polymorphs, a non-perovskite (-FAPbI ), which is a hexagonal yellow phase
(space group P6 mc), and a black perovskite phase (-FAPbI , space group P3m1) at room temperature.
The -FAPbI was slowly transformed to the thermodynamically stable -FAPbI . The -FAPbI consisted
4
inside the -FAPbI
3
crystal
3
3
2
3
3
3
3
3
3
of face-sharing octahedra propagating along the c-axis direction (Table S1 and Figure S2). The inorganic
layer was packed with an hcp-lattice and formed a 1D single chain. The spaces between the 1D inorganic
+
23
layers were filled with the FA cations. As mentioned in the Stoumpos report, the deviation from the ideal
+
symmetry can be attributed to the serious disordering of FA cations in the crystal structure. The prepared

-FAPbI
3
at a high temperature was quickly transformed into -FAPbI
3
by the cooling process at room
phase went back to its original
temperature. However, if it was heated at a high temperature, the -FAPbI
3
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form, -FAPbI
3
, and very slowly returned back into the -FAPbI crystal structure due to the partial loss of
3
FA resulting in a defective compound. Since the -FAPbI
3
is a more desirable structure as photoactive
material, which has a desirable band gap (1.48 eV) for photoelectric conversion and near-infrared
1
6
emission, it needs an additional process to suppress the formation of the -FAPbI
HAPbI and -FAPbI to create a mixed-cation perovskite, which stabilized the -FAPbI
decreased the band gap compared to the HAPbI (Figure 5a).
The HAPbI perovskite consisted of a layered tilted corner-sharing [PbI ] octahedral sheet that
3
phase. We combined
0
1
2
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8
9
0
1
2
3
4
5
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8
9
0
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9
0
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9
0
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3
4
5
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0
4
3
3
phase and further
4
4
-
4
6
propagated along the ac plane with the b axis to form the 3D structure. As the two NH bond on the
imidazolium group and alky ammonium group, respectively, and bridge the inorganic layers closer up
together, inorganic layers were stacked with the eclipsed mode with respect to one another (Figure 1b).
Similarly, inorganic layer of (HA)(FA)Pb
2
I
7
was stacked on top of another along the c-axis, whereas the
(Figure 1c-1d). The HR-TEM image
inorganic layer propagated in the ab plane direction unlike the HAPbI
4
4
-
of HAPbI
while the Pb atom show weaker contrast. The [002] plane image of a HAPbI
Figure 2a and matches the experimental atom positions. The quantitative match between experimental and
simulated data indicates that the HAPbI is composed of only single octahedral layer. For comparison, the
HR-TEM image of 2D layered (HA)(FA)Pb perovskite is shown in Figure 2c. We overlaid the [200]
plane image of the (HA)(FA)Pb on the HR-TEM result (Figure 2d). Two inorganic layers are extracted
from the experimental and simulated single crystal images. Therefore, 2D layered (HA)(FA)Pb
perovskite was well prepared from the combination of bication HAPbI and 3D -FAPbI
Figure 3a and 3b show the SEM images for the HAPbI , which exhibits the plate-like structure, consistent
with their 2D structure. Figure 3c shows SEM images of the stacked structure of these plate in the (HA)
3n1 crystal structures, which suggested that the bication HA induces the stacking of layered 2D
4
in Figure 2a shows a perfect octahedral structure of [PbI
6
] exhibiting higher contrast I atom
4
is (Figure 2b) overlaid on
4
I
2 7
I
2 7
I
2 7
4
3
.
4
(FA)n1Pb I
n
perovskite structures. The use of diammonium cations provided the bridges between the 2D layer
perovskites because it had the two positive cations. One was attached to itself, and the other could be
combined with other slabs. This created a 3D structure by stacking 2D slabs in one direction hierarchically.
The interactions between the bications and the 2D slabs was very strong, which resulted in the rigid and
stable structure. We have obtained the same laminated structure for the (HA)(MA)n1Pb
n
I3n1 (Figure 3d)
compound. We confirmed the elemental composition for the top region of the image in the Figure 3c using
3n1. Previous reports 41-45
the EDAX (Figure 3e). That well represents the composition of (HA)(FA)n1Pb I
n
demonstrated the 2D perovskite by using the diammonium cations. However, most were reported to be
limited to lower-dimensionality structures (from 2D layers to 0D inorganic motif). Recently, Mao et al.7
presented 2D layered DionJavobson (DJ) perovskites using the 3-AMP and 4-AMP cations (AMP =
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(
aminomethyl)piperidinium). These structures showed the stacking of inorganic layers as other inorganic
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layers stacked up on top of each other. Li et al. reported the successful synthesis of a broad series of 2D
perovskites, (NH )(CH NH 3n+1 (m = 4 ~ 9 and n = 1 ~ 4) using the diammonium cation.
3
C
m
H
2mNH
3
3
3
)
n−1Pb I
n
They confirmed a perfect vertical crystallite orientation in the film of an (NH
3
C
8
H16NH
3
)(CH
3
NH
3
)
2
Pb
I
3 10
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
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8
9
0
1
2
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1
2
3
4
5
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7
8
9
0
1
2
3
4
5
6
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8
9
0
compound.
SEM studies show the (HA)(MA)n1Pb
d) crystal structures, in which the consecutive 3D MAPbI
by the diammonium HA cations, forming the stacking of 3D MAPbI
n
I
3n1 (Figure 4a and 4b) and (HA)(FA)n1Pb
n
I3n1 (Figure 4c and
4
3
and -FAPbI perovskite sheets were connected
3
3
and -FAPbI
3
perovskites with
47
vertically. It is distinctively different from previous reported 2D Ruddlesden-Popper perovskites in which
thin layered rectangular plates generally were observed, leading to the low efficiency solar cell. Thus, the
crystal preferred growth direction with perpendicularly facilitate the movement of carriers in the thin film
1
0
of the solar cell, resulting in the improvement of solar cell efficiency.
We measured the UV-visible diffuse reflectance spectra for 2D layered perovskites and performed a
Kubelka-Munk transform to calculate the optical band gap. The band gap of 2D layered perovskite is shifted
to lower energies with increasing n value because of quantum confinement effect from dimensional
reduction of perovskite framework.48-49 The optical spectra of the HAPbI
(Figure 5a) exhibited a high-
4
energy absorption edge and a low-energy excitonic peak, which is a typical 2D perovskite property. The
exciton behavior arose from the dielectric confinement between the organic and inorganic layers to form a
quantum well excitonic structure in the perovskite structure. Thus, we assigned a band gap of HAPbI by
4
extrapolating the higher energy absorption edge to the energy axis. The most influence on the band gap is
the distortion of inorganic layer, represented by the equatorial PbIPb tilting angles related to the charge
transport. Since the valence band maximum (VBM) and conduction band minimum (CBM) of the 2D
hybrid perovskites are determined by the I5p states with the small amount of Pb 6s and Pb 6p states,50
respectively, as the bond angles of PbIPb were increased, the overlap of orbital between Pb s and I p
states become larger, resulting in the lowering the band gap. Herein, the bond angles of PbIPb in HAPbI
4
o
o
o
(156.17 and 178.05 ) with a more distorted structure from 180 has a higher band gap of 2.20 eV.
Compared with HAPbI , the band gaps of (HA)(FA)n1Pb
.80 eV, respectively. The excitonic peak disappeared in the 2D layered perovskites, (HA)(A)n1Pb
4
n
I
3n1 and (HA)(MA)n1Pb I3n1 are 1.64 eV and
n
1
n
I
3n1 (A
=
MA or FA). The excitonic absorption came from the long-lived excitonic state in the strong electric field
generated by the localized positive organic cation around the negatively charged inorganic layers in the
51
perovskite structure. The excitonic peak was expected to decrease with increasing n in the layered 2D
perovskite. It was observed that the 2D layered perovskites, (HA)(A)n1Pb 3n1 (A = MA or FA), had some
n
I
tailing at the absorption edge, which arose from the impurities of the higher order homologous members,9
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whereas the pure MAPbI
3
(1.48 eV) and black phase -FAPbI (1.41 eV) showed a sharp absorption edge,
3
which indicated the direct band gap materials.
Figure 5b and 5c show the optical constants, n and k (refractive index and extinction coefficient,
5
2
respectively), were extracted by simultaneously fitting a Cody-Lorentz oscillator model to the  and 
ellipsometry measurement taken at three different angles of incidence; 65, 70 and 75. The fits of
0
1
2
3
4
5
6
7
8
9
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1
2
3
4
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9
0
ellipsometry data at three angles of incidence are presented in Figure S3-S7. The n of (HA)PbI
peak around the band gap at 510 nm and the k of that is lower compared to other perovskites below the
band gap energy. However, the k of MAPbI shows the relatively high among the perovskites in the entire
wavelength range, indicating good light absorber material. This value for MAPbI corresponds to a very
high value of > 10 cm (Figure 5d) for above the range of band gap, which is well consistent with the
4
has a sharp
3
3
5
-1
5
3
previous report for MAPbI
has the broad k peak for the entire region of wavelength due to the its low band gap. Even though (HA)
3n1 peorvskite exhibits the highest n value among the perovskite, the k value was sharply
decreased as it approach band gap energy, which also was observed in the (HA)(FA)n1Pb 3n1 peorvskite
system. It indicates that the optical properties of 2D layered perovskites may be influenced by their parent
3
. The k and n values of -FAPbI
3
show the same trend as 3D MAPbI
3
, but it
(
MA)n1Pb I
n
n
I
2
D perovskite rather than 3D perovskite.
Figure 6a shows the powder XRD of MAPbI
3
, -FAPbI
3
, HAPbI
4
and 2D (HA)(A)n1Pb I3n1 (A = MA
n
or FA) perovskites. To confirm the orientation of the perovskite film, we measured XRD for the perovskite
film, of which preparation method was described in experimental section. The XRD patterns of
(HA)(A)n1Pb
n
I
3n1 (A = MA or FA, n = 2, 3 and 4) perovskite films (Figure 6b) exhibited two peaks around
4 and 28 , which reflected the (111) and (202) crystal planes, indicating the vertical orientation of
perovskite film with respect to the substrate.8, 54-55 Notably, the (HA)(MA)n1Pb
3n1 (n = 2, 3 and 4) films
o
o
1
n
I
were exclusively observed, clearly indicating the vertical well-aligned perovskite layers. Therefore, an
advantage of the diammonium based 2D perovskite is that they provide a significant opportunity to enhance
the charge transport into the electron collection layer with a direct route.
We measured PL spectroscopy to detect the emission property of 2D layered perovskites at room
temperature (Figure S8). All perovskites showed a single emission peak, in which the maximum PL peak
5
6
positions were well matched with the excitonic peaks in the absorption spectra (Figure 5a). We carried
out the measurement of the TRPL to determine the PL lifetime of the 2D perovskite. The time decay of the
fluorescence spectra was fitted with the exponential decay model in Figure 7a. The faster decay process (
represents the radiative recombination of exciton, while the slower decay process ( ,  and  ) is related
to the trap states formation due to the electron−phonon coupling in the layered perovskite. As shown in
Table 2, all compounds shows that  component contributes the most to PL lifetime because A value is in
1
)
2
3
4
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the range of 63.85% to 90.29%. However, HAPbI
perovskites have a very long slower decay process although they have a low contribution to PL lifetime.
For example, for (HA)(MA)n1Pb 3n1, it has a 1.5% for  (282 ns) component and (HA)(FA)n1Pb
perovskite shows a 1.07% for  (595 ns) component. As a consequence, a very long average PL lifetime
avg) was observed in (HA)(MA)n1Pb 3n1 perovskites (335 ns). To
4
, (HA)(MA)n1Pb
n
I
3n1, and (HA)(FA)n1Pb
n
I
3n1
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
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3
3
3
3
3
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3
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n
I
3
n 3n1
I
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
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8
9
0
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9
0
1
2
3
4
5
6
7
8
9
0
(

n
I
3n1 (197 ns), and (HA)(FA)n1Pb I
n
make our explanation more clear, the PL intensities for each component were summarized in Table S2 in
the supporting information. The PL intensity was calculated by multiplying the amplitude with lifetime.
The 
3
component (69.63%) for (HA)(MA)n1Pb
n
I3n1 and 
4
n 3n1
component (53.44%) for (HA)(FA)n1Pb I
show the highest values for the PL intensity. That is, even though they have the low percentage to the PL
lifetime, the PL intensity is quite high, resulting in very long average PL lifetime (avg). The PL lifetime of
(
HA)(MA)n1Pb
n
I
3n1 perovskite is approximately thirty five times that of the MAPbI
3
3
with 8.2 ns. This was
)(CH NH Pb
also significantly longer than the previous stacking 2D perovskites, (NH
3
m
C H2mNH
3
3
)
2
3
I
10 (m
4
6
58
=
7, 8, 9), (C
6
H
5
C
2
H
4
NH
3
)
2
PbI
4
·(CH
3
NH
3
PbI
3
)
n−1 (n = 1, 2, and 3) and A′(CH
3
NH
3
)
n–1Pb I3n+1 (A′ = 3-
n
7
(
aminomethyl)piperidinium (3AMP) or 4-(aminomethyl)piperidinium (4AMP)), which have shown a
carrier lifetime value between approximately 0.1 and 200 ps. The reason for the long PL lifetimes compare
to other 2Ds perovskites can be attributed that the recombination process between electron and hole
occurred very slowly due to their vertical stacking structure. Figure 7b shows the image mapping of PL
lifetime, which was measured by the direct excitation with 470 nm laser with a pulse width of ~ 30 ps to
generate excitation from the perovskite compounds. Through the scale bar of lifetime next to image
mapping, the PL lifetime of the 2D layered (HA)(FA)n1Pb
exhibited a much longer lifetime compared to that of the 3D MAPbI
consistent with the TRPL results. When we compared two 2D layered perovskites, interestingly, PL
emission of the (HA)(MA)n1Pb 3n1 perovskite shows significantly uniform, which was mainly consisted
of the long-lived emission, whereas that of (HA)(FA)n1Pb 3n1 is associated with initial fast decay and
long lifetimes, indicating non-uniformity of PL emission. Therefore, (HA)(MA)n1Pb 3n1 has a uniform
3n1 is non-uniform PL lifetime and should be more improved for
n
I
3n1 and (HA)(MA)n1Pb
n
I3n1 perovskites
3
and -FAPbI perovskites, which is
3
n
I
n
I
n
I
carrier density, while (HA)(FA)n1Pb I
n
practical applications.
To demonstrate that the 2D layered perovskite’s film would be an efficient light absorber, the energy
level of the perovskite layer with their interface layer in the photovoltaic device was determined using UPS
(
Figure 8a). The valence band and work function (W ) were calculated from the low binding energy level
F
and the secondary cut off edge region in the photoemission spectra, respectively. All energies were
referenced to an Au Fermi level (0 eV). The valence band energy level of the 2D layered perovskites were
slightly lower than the 2D (HAPbI
4
) and the 3D (MAPbI
3
and -FAPbI ) perovskites (Figure 8b). This lead
3
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to an increase in the ionization energy in the order of the 2D layered perovskites, the HAPbI , and the 3D
4
perovskite. However, the W
c), which indicated the increase of the Pb - related surface state. It tended to shift the Fermi level to a
conduction band minimum (CBM). Thus, the electron affinity, which is the difference between the W and
CBM, was 4.59 eV for the (HA)(FA)n1Pb 3n1 perovskite and 3.93 eV for the HAPbI compound. As
shown in Figure 8d, the CBM position of the 2D layered perovskites was a very close energy alignment
with the CBM of the TiO electron transporting layer compared to the other perovskites. No barrier for
electron extraction from the 2D layered perovskites to the TiO layer was expected. The barrier of the hole
F
of the 2D layered perovskites was the highest among the perovskites (Figure
o
59
8
F
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
n
I
4
2
2
extraction was predicted from the offset between the perovskite VBM and the HTL HOMO.60-61 In all of
the perovskites, the HOMO level of HTL was closer to the Fermi level than the perovskite VBM. Therefore,
none of perovskites exhibited a hole extraction barrier.
Film morphology, including grain size, crystal orientation, and coverage, are important factors in the
fabrication of high-efficiency solar cells. Figure 9 shows the SEM images of the (HA)PbI
3n1 perovskites films, respectively. The perovskite film made from
exhibits the uniform and compact morphology (Figure 9a). (HA)(MA)n1Pb 3n1 film displays
the similar film quality as (HA)PbI (Figure 9b). However, at the AFM images (Figure 9d and 9e) for the
4
, (HA)
(MA)n1Pb
n
I
3n1 and (HA)(FA)n1Pb I
n
(HA)PbI
4
n
I
4
surfaces shown in Figure 9a and 9b, there exists large grain size, which cause the formation of a pinhole
between the grain boundaries. It was an adverse effect on the performance of the photovoltaic effect. In
contrast, (HA)(FA)n1Pb
n
I
3n1 film demonstrates a much more uniform and small grain size (Figure 9c and
9
f). It indicates that grain growth of the (HA)(FA)n1Pb I
n
3n1 perovskite proceeds very slowly so that the
grain size is small and uniform and can eventually construct a compact thin film.62
We conducted a photovoltaic performance of the -FAPbI
3
, HAPbI
4
and (HA)(A)n1Pb I3n1 (A = MA or
n
FA) perovskites. The corresponding photocurrent density-voltage (J-V) curves under AM1.5G illumination
are shown in Figure 10, and the photovoltaic parameters are summarized in Table 3. First, we reveals that
we created solar cells in air. Generally, because perovskite is very sensitive to the humidity and oxygen in
air, perovskite solar cells are created in an inert atmosphere, making them ultimately unsuitable for
commercialization. As can be observed in Figure 10, the 2D layered perovskite cells demonstrate a
significantly higher performance compared to the HAPbI
4
based device. The device composed of HAPbI
4
exhibits low efficiency of 0.53% because the high exciton binding energy in 2D structure prohibits
separation of electron and hole pair. The (HA)(FA)n1Pb I3n1 perovskite based device shows performance
n
2
with a short current density (Jsc) of 16.70 mA/cm , a Voc of 0.76 V, a fill factor (FF) of 52.20% and a PCE
2
of 6.75%. The (HA)(MA)n1Pb
n
I
3n1 device exhibits 15.40 mA/cm , 0.77 V, 55.00% and 6.53% for Jsc, Voc,
FF and PCE, respectively. The -FAPbI
3
perovskite cell presents the 5.15%. However, the black phase of
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the film was slowly changed with the non-perovskite yellow phase, losing its efficiency quickly. The best
performance is the MAPbI cell that shows 8.23% of PCE. However, when exposed to air, they were quickly
degraded and lost efficiency while 2D layered perovskites showed excellent stability (Figure 10c).
The IPCE spectra and integrated Jsc value for (HA)(MA)n1Pb
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
3
n
I
3n1 and (HA)(FA)n1Pb I3n1 devices are
n
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
shown in Figure 10b. The current onset is the same as the absorbance spectra in Figure 5a, indicating that
there is no HA cation alloyed into the 3D perovskite phase. The slight increase of external quantum
efficiency (EQE) was observed in the (HA)(FA)n1Pb
n
n 3n1
I3n1 device compared to the (HA)(MA)n1Pb I
2
device due to the low band gap of -FAPbI
3
material. The integrated Jsc yield 16.26 mA/cm and 14.24
2
mA/cm for (HA)(FA)n1Pb
n
I
3n1 and (HA) (MA)n1Pb I3n1 devices, respectively, which are well agreement
n
with the J-V characteristic results. We conducted the stability test for the MAPbI
3
, (HA)(FA)n1Pb I3n1 and
n
2
(HA)(MA)n1Pb
n
I
3n1 devices under AM 1.5G irradiation of 100 mW/cm upon storage at ambient condition
(30 ~ 50% relative humidity) and temperature as shown in Figure 10c. MAPbI
3
device degraded to almost
2
0 day whereas the (HA)(FA)n1Pb 3n1 devices maintained 75% and 80% of its
n
I
3n1 and (HA) (MA)n1Pb I
n
initial efficiency, respectively, indicating that stacking framework retard the oxidation of perovskite in the
humidity condition. Thus, even though the 2D layered perovskite solar cells showed a low efficiency, we
anticipates that we can obtain stable and high efficiency solar cells if we can optimized the film morphology.
■
CONCLUSIONS
We choses small molecules of histamine to minimize the distance of the organic layers for the 2D perovskite.
The HAPbI had enough narrow band gaps to apply the solar cells and were also soluble in a wide range of
solvents. To make the layered 2D perovskites, (HA)(A)n1Pb 3n1 (A = MA or FA), we incorporated the
diammonium cation, histamine, into the 3D perovskite (MAPbI and FAPbI ), which not only exhibited
4
n
I
3
3
high stability but also facilitated the charge transport due to its hierarchical 3D structure type. The
interactions between the bications and the 2D slabs were very strong, which resulted in the rigid and stable
structure. These structures showed the stacking of inorganic layers because the other inorganic layers
stacked up on top of each other. This created a 3D structure by stacking the 2D slabs with one direction
hierarchically. We confirmed the hierarchical structure using the SC-XRD, the powder XRD, PL, and the
TRPL. The 2D layered perovskites, (HA)(A)n1Pb I3n1, exhibited a longer carrier lifetime compared to the
n
previous stacking 2D perovskite. When we prepared the solar cell with the 2D layered perovskites, the solar
cell based on the 2D layered perovskites showed a higher efficiency than the thin 2D perovskite. The reason
was the 2D layered perovskites, (HA)(A)n1Pb I3n1, exhibited a perfect vertical layer orientation and a long
n
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carrier lifetime, which is favorable in an electron transport, and showed an excellent performance for the
perovskite solar cell application compared to the thin 2D perovskite structure.
■
ACKNOWLEDGMENTS
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
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2
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5
6
7
8
9
0
This research was supported by the Basic Science Research Program through the National Research
Foundation of Korea (NRF) funded by the Ministry of Education (2016R1D1A1B04931751). This work
was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government
(MSIT) (2019R1A2C1003108). This research was supported by Nano·Material Technology Development
Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science,
ICT and Future Planning. (2009-0082580).
Supporting Information
Photographs of (HA)(FA)n1Pb
crystal data, structure refinement and crystal structure for 1D -FAPbI
parameters for MAPbI3, -FAPbI , HAPbI , (HA)(MA)n1Pb
Static photoluminescence of MAPbI , -FAPbI , HAPbI and 2D (HA)(A)n1Pb
perovskite single crystals. PL intensity ratio for each component of PL lifetime from the TRPL results of
MAPbI , -FAPbI , HAPbI and 2D (HA)(A)n1Pb 3n1 (A = MA or FA) perovskite single crystals.
Crystallographic files for HAPbI , (HA)(FA)Pb and -FAPbI perovskites (CIF).
n
I3n1, (HA)(MA)n1Pb
n
I
3n1, MAPbI
3
, -FAPbI
3
and HAPbI
4
single crystal,
3
perovskite, and ellipsometry
3
4
n
I
3n1 and (HA)(FA)n1Pb
n
I3n1 thin films.
3
3
4
n
I
3n1 (A = MA or FA)
3
3
4
n
I
4
2
I
7
3
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(
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(b)
6
7
8
9
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1
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1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
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7
8
9
0
1
2
3
4
5
6
7
8
9
0
I1
I1
H3
H2
4
.38 Å
I4
H1A
H1B
I2
(c)
(d)
Figure 1. Crystal structure of (a) HAPbI
protonated amine and adjacent four iodide ions of the inorganic [PbI
eclipsed conformation. (c) Side-view and (d) top-view of 2D layered (HA)(FA)Pb
4
, four hydrogen bond per histamine unit, formed between the
2

6
] layer. (b) Top-view of HAPbI
perovskite crystal
perovskite was overlaid on top of another
4
,
I
2 7
structure. The inorganic layer of 2D layered (HA)(FA)Pb
exactly.
I
2 7
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2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
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4
4
4
4
4
4
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6
(
200)
(
b)
(
a)
0
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2
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8
9
0
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7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
200)
(
d)
(
c)
Figure 2. (a) HR-TEM images of 2D HAPbI
overlaid on the image. (b) Crystal structure of HAPbI
layered (HA)(FA)Pb perovskite crystal. The [200] plane image of the (HA)(FA)Pb
image. (d) 2D layered (HA)(FA)Pb perovskite crystal structure with (200) direction.
4
perovskite crystal. The [002] plane image of a HAPbI
along the (200) direction. (c) HR-TEM image of 2D
is overlaid on the
4
is
4
2
I
7
I
2 7
I
2 7
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Table 1. Crystal data and structure refinement for HAPbI
4
and (HA)(FA)Pb
2
7
I .
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Empirical formula
HAPbI
4
(HA)(FA)Pb
460.92
2 7
I
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
827.96
298(2)
0.700
1
293(2)
0.700
Triclinic
P-1
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Monoclinic
P2 /n
1
Unit cell dimensions
a, Å
b, Å
8
2
9
.9020(18)
0.038(4)
.0050(18)
8.9100(18)
9.0510(18)
16.539(3)
86.20(3)
82.61
c, Å
, deg
90°
91.86(3)°
90°

, deg

, deg
89.08(3)
Volume (Å3)
1605.4(6)
4
1319.8(5)
2
Z
Density (calculated) (g/cm3)
Absorption coefficient (mm-1)
F(000)
3.425
17.304
1424
3.676
19.929
1
244
Crystal size (mm3)
θ range for data collection
0.120  0.098  0.075
0.40  0.61  0.92
2.002 to 33.645°
2.221 to 33.337°
-
12 ≤ h ≤ 12,
-12 ≤ h ≤ 12,
-13 ≤ k ≤ 13,
-23 ≤ l ≤ 23
Index ranges
-28 ≤ k ≤ 28,
-12 ≤ l ≤ 12
Reflections collected
19299
12864
Independent reflections
Completeness to theta = 24.835°
Refinement method
5106 [R(int) = 0.0391]
95.1 %
6815 [R(int) = 0.0467]
71.5 %
2
2
Full-matrix least squares on F
5106 / 0 / 120
1.060
Full-matrix least squares on F
6815 / 10 / 181
1.331
Data/restraints/parameters
Goodness-of-fit
R1 = 0.0405,
wR2 = 0.1078
R1 = 0.1253,
wR2 = 0.3391
Final R indices [I > 2σ(I)]
R1 = 0.0411,
wR2 = 0.1086
R1 = 0.1493,
wR2 = 0.3631
R indices [all data]
Extinction coefficient
0.0061(3)
-
-
3
Largest diff. peak and hole (e Å )
2.862 and -2.709
4.811 and -2.262
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(a)
(b)
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1
2
3
4
5
6
7
8
9
0
(c)
(d)
(e)
C Ka
N Ka
Pb Ma
I La
Figure 3. The SEM images of the (a) HAPbI
3n1 perovskite, (c) enlarged image of the square part (yellow dot line) in the (b) and (d) high
magnification image of 2D (HA)(FA)n1Pb 3n1 perovskite. (e) Elemental mapping for the
(HA)(MA)n1Pb 3n1 compound as shown in (d).
4
plate structure, (b) vertically layered 2D (HA)
(
MA)n1Pb I
n
n
I
n
I
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2
2
3
3
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3
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3
3
3
3
4
4
4
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0
1
2
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0
1
2
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4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(c)
(d)
Figure 4. SEM images of the vertical stacking structure of (a-b) 2D (HA)(MA)n1Pb
n
I3n1 and (c-d) 2D (HA)
(
FA)n1Pb I
n
3n1 perovskites.
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5
5
6
2
.8
.6
.4
2.2
.0
1.8
.6
MAPbI : 1.48 eV
3
MAPbI3

-FAPbI : 1.41 eV
(a)
3
(b)
HAPbI : 2.20 eV
-FAPbI3
4
2
(
HA)(MA)n-1Pb I : 1.80 eV
n 3n+1
HAPbI4
(
HA)(FA)n-1Pb I : 1.64 eV
n 3n+1
(HA)(MA)n-1Pb I
0
1
2
3
4
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6
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1
2
3
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n 3n+1
2
(HA)(FA)n-1Pb I
n 3n+1
2
1
3
00 400 500 600 700 800 900 1000
1.2
1.6
2.0
2.4
Energy (eV)
2.8
3.2
Wavelength (nm)
3
.5
1
.0
.8
0.6
.4
.2
.0
MAPbI3
MAPbI3
-FAPbI3
(d)
(
c)
3
.0
-FAPbI3

0
HAPbI4
(HA)(MA) Pb I
n-1 n 3n+1
HAPbI4
2
.5
.0
.5
.0
.5
.0
(HA)(MA) Pb I
n-1
n 3n+1
(HA)(FA) Pb I
(HA)(FA) Pb I
n-1 n 3n+1
n-1
n 3n+1
2
1
0
1
0
0
0
0
3
00 400 500 600 700 800 900 1000
3
00 400 500 600 700 800 900 1000
Wavelength (nm)
Wavelength (nm)
Figure 5. (a) UV-visible diffuse reflectance spectra, (b) real, n, refractive index, (c) imaginary, k, refractive
index, and (d) adsorption coefficient for the MAPbI
3
, -FAPbI
3
, HAPbI
4
and 2D (HA)(A)n1Pb I3n1 (A =
n
MA or FA) perovskites.
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MAPbI3
-FAPbI3
(
a)

(
(
HA)PbI4
HA) (MA) Pb I
n 3n+1
2
n-1
1
1
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1
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2
2
2
2
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5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(HA) (FA) Pb I
n 3n+1
2
n-1
5
10 15 20 25 30 35 40 45 50 55 60
2
theta (degree)
Glass substrate
(
b)
(
HA)(FA)Pb2I7
(111)
(202)
(HA)(FA) Pb I
2
3 10
(
(
(
(
HA)(FA) Pb I
3
4 13
HA)(MA)Pb2I7
HA)(MA) Pb I
2
3 10
HA)(MA) Pb I
3
4 13
5
10 15 20 25 30 35 40 45 50 55 60
2
theta (degree)
Figure 6. (a) Powder X-ray diffraction of MAPbI
or FA) perovskites and (b) X-ray diffraction pattern of the perovskite films of (HA)(FA)n1Pb
, 4) and (HA)(MA)n1Pb 3n1 (n = 2, 3, 4) coated on glass substrate.
3
, -FAPbI
3
, HAPbI
4
and 2D (HA)(A)n1Pb
n
I
3n1 (A = MA
n
I
3n1 (n = 2,
3
n
I
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2
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(
a)
Decay
Fit
Decay
Fit
Decay
Fit
MAPbI
3
-FAPbI
3
HAPbI
4
ꢋꢌꢍꢎ ꢂ 2.86 ns
ꢋꢌꢍꢎ ꢂ 4 ns
ꢋꢌꢍꢎ ꢂ 105 ns
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
0
20
40
60
80
100
0
100
200
300
400
500
0
10
20
30
40
50
60
Time (ns)
Time (ns)
Time (ns)
400
Decay
Fit
Decay
Fit
MAPbI
-FAPbI3
(HA)PbI4
HA)(MA)n-1Pb I
3

(HA)(MA)n-1Pb
n
I
3n+1
(
HA)(FA)n-1Pb
n
I
3n+1
300
(
n 3n+1
ꢋꢌꢍꢎ ꢂ 197 ns
ꢋꢌꢍꢎ ꢂ 335 ns
(HA)(FA)n-1Pb I
n 3n+1
2
00
100
0
0.0
0.2
0.4
0.6
0.8
1.0
0
500
1000
1500
2000
Perovskites
Time (s)
Time (ns)
(
b)
MAPbI
3
-FAPbI
3
HAPbI
4
(HA)(MA) n-1Pb
n
I
3n+1
(HA)(FA) n-1Pb
n
I
3n+1
(HA)(FA)n-1Pb
n
I
3n+1
Figure 7. (a) Transient photoluminescence of MAPbI
3
, -FAPbI
3
, HAPbI
4
and 2D (HA)(A)n1Pb I3n1 (A
n
=
MA or FA) perovskites single crystals and (b) image mapping of the PL emission decay corresponding to
each TRPL in Figure 7(a)
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Table 2. Photoluminescence lifetime results of MAPbI
3
, -FAPbI
3
, HAPbI
4
n 3n1
and 2D (HA)(A)n1Pb I
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(A = MA or FA) perovskites from the transient photoluminescence.
Perovskites
MAPbI
A
1
/%

1
/ns
A
2
/%

2
/ns
A
3
/%

3
/ns
A
4
/%

4
/ns

avg/ns
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
3
63.85 0.96
90.29 0.30
33.40
8.69
2.83
1.91
4.70
4.90
2.75
8.20
2.86
4.00
-FAPbI
HAPbI
3
1.03 13.00
1.99 164.00
1.50 282.00
4
78.10 1.10
19.91
18.36
105.00
197.00
(
HA)(MA)n1Pb
HA)(FA)n1Pb
n
I
3n1 80.13 1.10
(
n
I
3n1
79.48 1.60
16.84 12.00 2.61 82.00
1.07
595.00
335.00
The emission decay was analyzed using the equation: Iꢀtꢁ ꢂ ꢄ expꢀꢐꢑ⁄ꢋ ꢁ ꢒꢃꢄ expꢀꢐꢑ⁄ꢋ ꢁ ꢒ
ꢏ
ꢏ
ꢓ
ꢓ
ꢃꢄ expꢀꢐꢑ⁄ꢋ ꢁ ꢒ ∙∙∙, where ∑ ꢄ /ꢀꢄ ꢒ ꢄ ꢒ ꢄ ꢒ∙∙∙ꢁ ꢂ 1,ꢃꢃthe average lifetime, <>, is defined by
ꢔ
ꢔ
ꢅ
ꢅ
ꢏ
ꢓ
ꢔ
ꢓ
〈
ꢋ〉 ꢂ ∑ ꢄ ꢋ ⁄∑ ꢄ ꢋ and amp is the amplitude of the average lifetime.
ꢅ ꢅ ꢅ ꢅ ꢅ ꢅ
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MAPbI3
(b)
(
a)

-FAPbI3
HAPbI4
(
HA)(MA)n-1Pb I
n 3n+1
(
HA)(FA)n-1Pb I
n 3n+1
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1
2
3
4
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6
7
8
9
0
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8
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1
2
3
4
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0
1
2
3
4
5
6
7
8
9
0
Homo Level
.60
.62
.19
1
1
Low binding
energy region
Cutoff
region
MAPbI3
-FAPbI3
HAPbI4
1
1.35
1.22
(
(
HA)(MA)n-1PbnI
3n+1
HA)(FA)n-1PbnI
3n+1
2
2 20 18 16 14 12 10 8 6 4 2 0 -2
5
4
3
2
1
0
Binding Energy (eV)
Binding energy (eV)
MAPbI3
(d)
(c)

-FAPbI3
HAPbI4
HA)(MA) Pb I
3.93
4.29
(
n-1
n 3n+1
4.1
4
.36
4
.59
5
.94
(HA)(FA) Pb I
FTO
‐4.5
n-1
n 3n+1
4
.78
4
.75
Au
4
.62
.63
‐5.1
5
.20
4
5
.84
5
.94
4
.45
6.13
6.25 6.05
7.3
3.2
3.6
4.0
4.4
4.8
5.2
5.6
Kinetic energy (eV)
Figure 8. (a) UPS spectra of MAPbI
3
, -FAPbI
3
, HAPbI
4
and 2D (HA)(A)n1Pb I3n1 (A = MA or FA)
n
perovskites on FTO substrate, (b) UPS spectra of the top of occupied states, i.e., HOMO level for the 2D
perovskites, (c) work function from the cut off edge region of photoemission spectra and (d) energy level
of MAPbI
3
, -FAPbI
3
, HAPbI
4
and 2D (HA)(A)n1Pb I3n1 (A = MA or FA) perovskites for the
n
FTO/TiO /perovskites/spiro-MeOTAD/Au heterojunction solar cell configuration.
2
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(
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(b)
(c)
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
nm
nm
m
0
.4
200
(d)
(e)
(
f)
100
1
00
0
50
0
0
-
0.4
-
100
-50
-
0.8
-200
-100
5
m
5 m
5
m
-
300
-150
-
1.2
Figure 9. (a) SEM images of the (a) HAPbI
perovskites films onto the FTO/TiO blocking layer/TiO
e) (HA)(MA)n1Pb 3n1 films measured on the same surface as shown in the
SEM images (a) (b) and (c), respectively.
4
, (b) (HA)(MA)n1Pb
n
I
3n1 and (c) (HA)(FA)n1Pb
n
I
3n1
2
2
mesophorous layer. AFM images of (d) (HA)PbI ,
4
(
n
I
3n1 and (f) (HA)(FA)n1Pb I
n
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2
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2
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3
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3
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3
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Air Fabrication
2
0
100
20
(
a)
(
b)
2
1
6.26 mA/cm
80
16
15
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
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7
8
9
0
1
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0
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5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
1
4.24 mA/cm
60
12
1
0
5
0
MAPbI3
-FAPbI3

HAPbI4
40
8
4
(HA)(MA)n-1Pb I
n 3n+1
(HA)(FA)n-1Pb I
n 3n+1
20
(
HA)(FA)n-1Pb I
n 3n+1
(HA)(MA)n-1Pb I
n 3n+1
0
0
900
0
.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
400
500
600
700
800
Photovoltage (V)
Wavelength (nm)
(c)
10
80
60
40
(
HA)(MA)n-1Pb I
n 3n+1
(
HA)(FA)n-1Pb I
8
6
4
2
n 3n+1
MAPbI3
(HA)(MA)n-1Pb I
n 3n+1
(HA)(FA)n-1Pb I
n 3n+1
MAPbI3
20
0
5
10
15
20
0
5
10
15
20
Time (day)
Time (day)
1
.0
.8
.6
20
16
12
8
4
0
0
(HA)(MA)n-1Pb I
n 3n+1
(HA)(MA)n-1Pb I
n 3n+1
0
.4
(HA)(FA)n-1Pb I
n 3n+1
(HA)(FA)n-1Pb I
MAPbI3
n 3n+1
MAPbI3
0.2
0
5
10
15
20
0
5
10
15
20
Time (day)
Time (day)
Figure 10. (a) Photovoltaic performance (J-V curve obtained from forward scan) of the perovskite solar
cell made with MAPbI , -FAPbI , HAPbI and 2D (HA)(A)n1Pb 3n1 (A = MA or FA) perovskites under
simulated AM (air mass) 1.5G (global) illumination (100 mW cm ). (b) External quantum efficiency (EQE)
spectra of the 2D (HA)(A)n1Pb 3n1 (A = MA or FA) perovskites devices with short circuit photocurrent
density estimated by integrating the EQE. (c) Evolution of photovoltaic performances based on MAPbI
and 2D (HA)(A)n1Pb
3n1 (A = MA or FA) perovskites films under AM 1.5G irradiation of 100 mW/cm2
upon storage at ambient condition (30 ~ 50% relative humidity) and temperature.
3
3
4
n
I
-2
n
I
3
n
I
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Table 3. The photovoltaic parameters of solar cells using MAPbI
3
, -FAPbI
3
, HAPbI and 2D (HA)
4
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
A)n1Pb
n
I
3n1 (A = MA or FA) perovskites consisting of FTO/compact TiO
2
/mesoporous
TiO
2
/perovskite/spiro-MeOTAD/Au, which was fabricated in the ambient air.
Jsc
Voc
V]
FF
[%]

[%]
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Perovskites
MAPbI
2
[
[mA/cm ]
3
17.70
16.04
2.16
0.75
0.77
0.77
0.77
0.76
61.90
42.00
32.17
55.00
52.20
8.23
-FAPbI
HAPbI
3
5.15
0.53
6.53
6.75
4
(
HA)(MA)n1Pb
HA)(FA)n1Pb
n
I
3n1
15.40
16.70
(
n
I
3n1
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■ REFERENCES
(
1) Fu, Y.; Meng, F.; Rowley, M. B.; Thompson, B. J.; Shearer, M. J.; Ma, D.; Hamers, R. J.; Wright, J.
C.; Jin, S. Solution Growth of Single Crystal Methylammonium Lead Halide Perovskite Nanostructures for
Optoelectronic and Photovoltaic Applications. J. Am. Chem. Soc. 2015, 137 (17), 5810-5818.
(2) Stranks, S. D.; Eperon, G. E.; Grancini, G.; Menelaou, C.; Alcocer, M. J. P.; 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 (6156), 341-344.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
3) Xing, G.; Mathews, N.; Sun, S.; Lim, S. S.; Lam, Y. M.; Grätzel, M.; Mhaisalkar, S.; Sum, T. C. Long-
Range Balanced Electron- and Hole-Transport Lengths in Organic-Inorganic CH NH PbI . Science 2013,
42 (6156), 344-347.
4) D’Innocenzo, V.; Grancini, G.; Alcocer, M. J. P.; Kandada, A. R. S.; Stranks, S. D.; Lee, M. M.;
3
3
3
3
(
Lanzani, G.; Snaith, H. J.; Petrozza, A. Excitons versus free charges in organo-lead tri-halide perovskites.
Nat. Commun. 2014, 5.
(
5) Duong, T.; Wu, Y.; Shen, H.; Peng, J.; Fu, X.; Jacobs, D.; Wang, E.-C.; Kho, T. C.; Fong, K. C.; Stocks,
M.; Franklin, E.; Blakers, A.; Zin, N.; McIntosh, K.; Li, W.; Cheng, Y.-B.; White, T. P.; Weber, K.;
Catchpole, K. Rubidium Multication Perovskite with Optimized Bandgap for Perovskite-Silicon Tandem
with over 26% Efficiency. Adv. Energy Mater. 2017, 7 (14), 1700228.
(6) Yang, W. S.; Park, B.-W.; Jung, E. H.; Jeon, N. J.; Kim, Y. C.; Lee, D. U.; Shin, S. S.; Seo, J.; Kim, E.
K.; Noh, J. H.; Seok, S. I. Iodide management in formamidinium-lead-halide–based perovskite layers for
efficient solar cells. Science 2017, 356 (6345), 1376-1379.
(
7) Mao, L.; Ke, W.; Pedesseau, L.; Wu, Y.; Katan, C.; Even, J.; Wasielewski, M. R.; Stoumpos, C. C.;
Kanatzidis, M. G. Hybrid Dion–Jacobson 2D Lead Iodide Perovskites. J. Am. Chem. Soc. 2018, 140 (10),
775-3783.
8) Cao, D. H.; Stoumpos, C. C.; Farha, O. K.; Hupp, J. T.; Kanatzidis, M. G. 2D Homologous Perovskites
3
(
as Light-Absorbing Materials for Solar Cell Applications. J. Am. Chem. Soc. 2015, 137 (24), 7843-7850.
(9) Stoumpos, C. C.; Cao, D. H.; Clark, D. J.; Young, J.; Rondinelli, J. M.; Jang, J. I.; Hupp, J. T.;
Kanatzidis, M. G. Ruddlesden–Popper Hybrid Lead Iodide Perovskite 2D Homologous Semiconductors.
Chem. Mater. 2016, 28 (8), 2852-2867.
(
10) Tsai, H.; Nie, W.; Blancon, J.-C.; Stoumpos, C. C.; Asadpour, R.; Harutyunyan, B.; Neukirch, A. J.;
Verduzco, R.; Crochet, J. J.; Tretiak, S.; Pedesseau, L.; Even, J.; Alam, M. A.; Gupta, G.; Lou, J.; Ajayan,
P. M.; Bedzyk, M. J.; Kanatzidis, M. G.; Mohite, A. D. High-efficiency two-dimensional Ruddlesden–
Popper perovskite solar cells. Nature 2016, 536, 312.
(
11) Smith, I. C.; Hoke, E. T.; Solis-Ibarra, D.; McGehee, M. D.; Karunadasa, H. I. A Layered Hybrid
Perovskite Solar-Cell Absorber with Enhanced Moisture Stability. Angew. Chem. Int. Ed. 2014, 126 (42),
1414-11417.
12) Calabrese, J.; Jones, N. L.; Harlow, R. L.; Herron, N.; Thorn, D. L.; Wang, Y. Preparation and
1
(
Characterization of Layered Lead Halide Compounds. J. Am. Chem. Soc. 1991, 113 (6), 2328-2330.
(13) Soe, C. M. M.; Stoumpos, C. C.; Kepenekian, M.; Traoré, B.; Tsai, H.; Nie, W.; Wang, B.; Katan, C.;
Seshadri, R.; Mohite, A. D.; Even, J.; Marks, T. J.; Kanatzidis, M. G. New Type of 2D Perovskites with
Alternating Cations in the Interlayer Space, (C(NH
Photovoltaic Performance. J. Am. Chem. Soc. 2017, 139 (45), 16297-16309.
14) Koh, T. M.; Fu, K.; Fang, Y.; Chen, S.; Sum, T. C.; Mathews, N.; Mhaisalkar, S. G.; Boix, P. P.; Baikie,
2
)
3
)(CH
3
NH
3
)
n
Pb
n
I3n+1: Structure, Properties, and
(
T. Formamidinium-Containing Metal-Halide: An Alternative Material for Near-IR Absorption Perovskite
Solar Cells. J. Phys. Chem. C 2014, 118 (30), 16458-16462.
(15) Pang, S.; Hu, H.; Zhang, J.; Lv, S.; Yu, Y.; Wei, F.; Qin, T.; Xu, H.; Liu, Z.; Cui, G. NH
An Alternative Organolead Iodide Perovskite Sensitizer for Mesoscopic Solar Cells. Chem. Mater. 2014,
6 (3), 1485-1491.
2
CH═NH
2
PbI :
3
2
28
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Page 29 of 32
Langmuir
1
2
3
(16) Eperon, G. E.; Stranks, S. D.; Menelaou, C.; Johnston, M. B.; Herz, L. M.; Snaith, H. J.
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Formamidinium lead trihalide: a broadly tunable perovskite for efficient planar heterojunction solar cells.
Energy Environ. Sci. 2014, 7 (3), 982-988.
(
17) Seol, D.-J.; Lee, J.-W.; Park, N.-G. On the Role of Interfaces in Planar-Structured HC(NH
2
)
2
PbI
3
Perovskite Solar Cells. ChemSusChem 2015, 8 (14), 2414-2419.
(18) Pellet, N.; Gao, P.; Gregori, G.; Yang, T.-Y.; Nazeeruddin, M. K.; Maier, J.; Grätzel, M. Mixed-
Organic-Cation Perovskite Photovoltaics for Enhanced Solar-Light Harvesting. Angew. Chem. Int. Ed. 2014,
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
5
3 (12), 3151-3157.
19) Jeon, N. J.; Noh, J. H.; Yang, W. S.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. I. Compositional engineering
of perovskite materials for high-performance solar cells. Nature 2015, 517, 476.
20) McMeekin, D. P.; Sadoughi, G.; Rehman, W.; Eperon, G. E.; Saliba, M.; Hörantner, M. T.;
(
(
Haghighirad, A.; Sakai, N.; Korte, L.; Rech, B.; Johnston, M. B.; Herz, L. M.; Snaith, H. J. A mixed-cation
lead mixed-halide perovskite absorber for tandem solar cells. Science 2016, 351 (6269), 151-155.
(
21) Lee, J.-W.; Kim, D.-H.; Kim, H.-S.; Seo, S.-W.; Cho, S. M.; Park, N.-G. Formamidinium and Cesium
Hybridization for Photo- and Moisture-Stable Perovskite Solar Cell. Adv. Energy Mater. 2015, 5 (20),
501310.
22) Yi, C.; Luo, J.; Meloni, S.; Boziki, A.; Ashari-Astani, N.; Grätzel, C.; Zakeeruddin, S. M.;
Röthlisberger, U.; Grätzel, M. Entropic stabilization of mixed A-cation ABX metal halide perovskites for
1
(
3
high performance perovskite solar cells. Energy Environ. Sci. 2016, 9 (2), 656-662.
(23) 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 (15), 9019-9038.
(
24) Wang, Z.; Zhou, Y.; Pang, S.; Xiao, Z.; Zhang, J.; Chai, W.; Xu, H.; Liu, Z.; Padture, N. P.; Cui, G.
Additive-Modulated Evolution of HC(NH
2
)
2
PbI Black Polymorph for Mesoscopic Perovskite Solar Cells.
3
Chem. Mater. 2015, 27 (20), 7149-7155.
(25) Weller, M. T.; Weber, O. J.; Frost, J. M.; Walsh, A. Cubic Perovskite Structure of Black
Formamidinium Lead Iodide, α-[HC(NH ]PbI , at 298 K. J. Phys. Chem. Lett. 2015, 6 (16), 3209-3212.
26) Jiang, S.; Luan, Y.; Jang, J. I.; Baikie, T.; Huang, X.; Li, R.; Saouma, F. O.; Wang, Z.; White, T. J.;
Fang, J. Phase Transitions of Formamidinium Lead Iodide Perovskite under Pressure. J. Am. Chem. Soc.
018.
27) Han, Q.; Bae, S.-H.; Sun, P.; Hsieh, Y.-T.; Yang, Y.; Rim, Y. S.; Zhao, H.; Chen, Q.; Shi, W.; Li, G.;
2
)
2
3
(
2
(
Yang, Y. Single Crystal Formamidinium Lead Iodide (FAPbI ): Insight into the Structural, Optical, and
3
Electrical Properties. Adv. Mater. 2016, 28 (11), 2253-2258.
(
28) Ma, F.; Li, J.; Li, W.; Lin, N.; Wang, L.; Qiao, J. Stable α/δ phase junction of formamidinium lead
iodide perovskites for enhanced near-infrared emission. Chem. Sci. 2017, 8 (1), 800-805.
29) Shin, J. W.; Eom, K.; Moon, D. BL2D-SMC, the supramolecular crystallography beamline at the
Pohang Light Source II, Korea. J. Synchrotron Rad. 2016, 23, 369-373.
30) Otwinowski, Z.; Minor, W., in Methods in Enzymology. Academic Press, New York: 1997; Vol. 276,
(
(
p 307.
(31) Sheldrick, G. M. SHELXT - Integrated space-group and crystal-structure determination. Acta
Crystallogr., Sect. A: Found. Crystallogr. 2015, 71 (1), 3-8.
(
32) Sheldrick, G. M. Crystal structure refinement with SHELXL. Acta Crystallogr., Sect. C: Cryst. Struct.
Commun. 2015, 71, 3-8.
33) Gate, L. F. Comparison of the Photon Diffusion Model and Kubelka-Munk Equation with the Exact
(
Solution of the Radiative Transport Equation. Appl. Opt. 1974, 13 (2), 236-238.
(34) Kim, H.-S.; Lee, J.-W.; Yantara, N.; Boix, P. P.; Kulkarni, S. A.; Mhaisalkar, S.; Grätzel, M.; Park,
N.-G. High Efficiency Solid-State Sensitized Solar Cell-Based on Submicrometer Rutile TiO
CH NH PbI Perovskite Sensitizer. Nano Lett. 2013, 13 (6), 2412-2417.
35) Knutson, J. L.; Martin, J. D.; Mitzi, D. B. Tuning the Band Gap in Hybrid Tin Iodide Perovskite
Semiconductors Using Structural Templating. Inorg. Chem. 2005, 44 (13), 4699-4705.
2
Nanorod and
3
3
3
(
29
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