Chemistry of Materials
Article
C(Bi) = 2.5 M, and T = 60 °C for (NH ) Bi I (flat hexagonal thin
EXPERIMENTAL SECTION
4
3
2 9
■
plates); and EC:HI:H O = 5:1.75:10, C(Bi) = 0.33 M, and T = 60 °C
2
Materials and Methods. Methylammonium iodide (MAI,
Dyesol), formamidinium iodide (FAI, Dyesol), methylammonium
bromide (MABr, Dyesol), lead iodide (PbI , 99.9%, “Lanhit”
for Cs Bi I (small hexagonal crystals).
3
2 9
To control the nucleation of crystals, the initial solution should be
filtered through a 0.22 μm-pore-size PTFE filter and poured into a vial
that was primarily cleaned using “Piranha solution” (H O :H SO =
2
supplier) and lead bromide (PbBr , 99.99%, “Lanhit” supplier),
2
2
2
2
4
propylene carbonate (PC, 99.99%, Sigma Aldrich), ethylene
carbonate (EC, 99%, “Himmed” supplier) were commercially
purchased and used without further purification. The 57 wt %
1
:3) and then triple rinsed using distilled water and dried. As a result,
surface nucleation was suppressed and only one or a few crystals
aqueous hydroiodic acid (HI ) of Pro analysis grade without any
aq.
Characterization. Powder XRD patterns were collected using a
Rigaku D/MAX 2500 (Japan) diffractometer with a rotating copper
anode, CuKα irradiation. XRD patterns were recorded in the 3−60°
stabilizing reducing additives was stored under hydrogen in a
refrigerator at 0 °C to avoid oxidation. Butylammonium iodide was
synthesized from butyl amine (99.8%, Pro analysis grade, “Himmed”
supplier) and HIaq. as reported elsewhere.
All syntheses and procedures were conducted under ambient
conditions (30−55% humidity, 23−25 °C).
General Synthetic Procedures of Single Crystals. MAPbI3
single crystals were grown from solvents mixtures of a cyclic
carbonate (PC or EC) with aqueous concentrated hydroiodic acid
2
θ range with a 0.02° step. The obtained single crystals were ground
36
in a mortar, and then the powder diffraction pattern was measured.
The profile analysis was carried out for each pattern using Jana 2006
software to refine the parameters of the unit cells. The goodness of fit
(
57% HI ) and, in some cases, additional volume of water. The
aq.
The absorption spectra of the ground crystals were recorded in
the diffuse reflectance mode using a Perkin Elmer Lambda 950 UV−
vis spectrophotometer. Measurements were performed at 298 K in the
spectral range of 250−1000 nm, with a scanning rate of 2.5 nm/s. The
optical band gap was determined from processing the data in the Tauc
plot coordinates.
mixture of solvents was prepared immediately prior to dissolution and
added to already weighed powders of MAI and PbI (1,1) in a vial or
a small beaker. The total volume of the mixed solvent was taken so as
to prepare the resulting solution of concentration 1−2% lower than
2
0
2
Table S1). The dissolution step was conducted under intense stirring
at the temperature from 30 to 60 °C chosen exactly the same as for
the entire subsequent crystallization process. After a complete
dissolution (5 min was usually enough), the clear yellow solution
was filtered through a membrane syringe filter (poly-
Steady-state PL measurements were performed on a home-built
microscope assembled using Thorlabs optomechanical components.
Samples were photoexcited using a 455 nm laser (InTop, Russia)
delivering 30 ps (FWHM) pulses, driven at repetition rates from 100
kHz up to 10 MHz or in the continuous wave mode. A Flame (Ocean
Optics, UK) spectrometer was used to record PL spectra.
(tetrafluoroethylene) (PTFE), 0.22 μm pore size) and poured into
a clean vial with a flat bottom. To facilitate the release of the CO2
forming under hydrolysis, the cap of vial was pierced with a syringe
needle. Then the vial was kept still at the same temperature to grow
the crystals. After a certain period (3−8 h, depending on the specific
growth conditions), the crystals were isolated from the solution,
blotted to dry with a lint-free cloth and washed with a dry ether.
For time-resolved photoluminescence (TRPL) measurements, a
microscope was coupled to the time-correlated single-photon
counting setup based on an SPC-150 module and an HMP-100-50
detector (Becker&Hickl, Germany). The required spectral band was
selected using a ML44 monochromator (Solar, Belarus). For every
sample under investigation, multiple points were examined to ensure
the representative sampling. Charge carrier lifetimes were determined
using a triple-exponential decay model.
The single crystals of FA MA
PbI , MAPb(Br I
) ,
x
(1 − x)
3
y (1 − y) 3
FA MA(1 − x)Pb(BryI(1 − y))3 were obtained by the same procedure
x
1
where solid precursors (AX, PbX ) were taken in a desired ratio. The
H NMR spectra were recorded using a Bruker Avance-III
2
concentration of saturated solutions in the case of substitution of MA
for FA slightly exceeded the values given in the Table S1. In the case
of substitution of I for Br, the solubility gradually decreased with an
increase of the Br fraction starting from the ratio I/Br = 1.5. The
following optimal conditions were determined for the rapid growth of
spectrometer with a 600.13 MHz proton frequency. The test solvent
mixture containing 500 μL of PC, 75 μL of HI , and 108 μL of D O
aq.
2
(the molar ratio water/PC was 1:50, where water includes both H O
2
from and D O) was maintained at 70 °C during 14 h. Spectra were
2
acquired at T = 298 K. Mean time for measurement of one spectra
1
−2 mm sized single crystals of 3D APbX perovskites (except for the
was 10−15 min. Chemical shifts were measured relatively to residual
3
pure FAPbI and MAPbBr ): T = 50 ± 5 °C, ω = 0.55 ± 0.05 and HI
signal of H
ppm).
2
O or hydrogen-deuterium oxide (HDO) (δ = 5.0−5.1
3
3
0
(HBr) concentration from 0.7 to 1.0 M.
MAPbBr3 single crystals were grown from a solvent mixture
GC−MS measurements were performed on a system consisting of
an GCMS-QP2010 Ultra (Shimadzu, Japan) gas chromatograph with
a quadrupole mass spectrometric detector. The components were
separated on an CP Sil 5 CB capillary column (25 m × 0.25 mm, 0.4
μm) with a stationary phase based on methyl (95%)−phenyl (5%)−
polysiloxane. The experimental data were processed using the
containing N,N′-dimethylurea (DMU) and aqueous concentrated
HBr solution (48% HBr ) with a molar ratio DMU:HBr:H O =
aq.
2
1
.0:0.7:3.5 in the resulting mixed solvent. Then, under vigorous
stirring at 60 °C, the mixed solvent was poured onto the weighed
portions of methylammonium bromide (MABr) and lead acetate
trihydrate (Pb(OAc)·3H O), so that the concentration of the final
2
solution was 0.8 M. The mixture was left on a plate heated to 60 °C
for 10 h, after which the grown crystals were removed from the
solution, washed with ether, and dried.
ASSOCIATED CONTENT
■
Single crystals of 2D layered perovskites (BA) (MA)
Pb I
2
n − 1
n 3n + 1
*
sı Supporting Information
were grown from slightly undersaturated solutions based on acidified
PC:H O mixtures with the BAI:MAI:PbI stoichiometry strictly
2
2
corresponding to the desired layer number n. The best crystals were
obtained from the mixtures with ω = 0.5−0.6 at a temperature range
0
Detailed solubility data and investigation of solvent
conversion, including the kinetic dependence of
solubility, comparison of crystallization mechanisms
from 40 to 50 °C.
The single crystals of different iodobismuthates were grown from
EC−H O solutions with an enhanced mole fraction of water (and
2
1
with related systems, and raw H NMR and GC−MS
acid). The following conditions were found to be optimal: molar ratio
data; estimation of the yield of single crystals; X-ray
characterization of the grown crystals; absorption and
PL spectra of the grown crystals of 3D and 2D (layered)
EC:HI:H O = 10:2:11, C(Bi) = 0.9 M, and T = 60 °C for MA Bi I
2
3
2 9
(
=
hexagonal crystals); EC:HI:H O = 10:1.8:10, C(Bi) = 0.71 M, and T
50 °C for FA Bi I (hexagonal crystals); EC:HI:H O = 5:1.8:10,
3 2 9 2
2
F
Chem. Mater. XXXX, XXX, XXX−XXX