Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.201700357
FULL PAPER
Synthesis, Crystal Structure and Optical Properties of the
Hexagonal Perovskites Variants ABX ; (B = Ni: A = Gu, FA, MA, X
3
=
Cl, Br; B = Mn, A = MA, X = Br)
Michael Daub,[a,b] Ines Ketterer, and Harald Hillebrecht*
[a]
[a,b]
Dedication Prof. Dr. Thomas Schleid on the occasion of his 60th birthday
Abstract :Herein we report on our systematic investigations on the
humidity but also to oxygen. It has been shown that through self-
doping with Sn(IV) the efficiencies of these PSC´s are reduced,
and therefore the observed efficiencies are not as high as
intended.[4] Through the diagonal relationship to Pb with respect
to its position in the periodic table, Bi (and Sb) compounds appear
to be interesting candidates as well. In the field of bismuth based
solution processed synthesis and characterization of transition metal
halides with the composition ABX
3
; A = organic cation; B = Mn, Ni; X
=
Cl, Br. For the guanidinium, formamidinium and methylammonium
nickel bromides and chlorides as well as for methylammonium
manganese bromide. The investigations were carried out with respect
to possible applications of 3d transition metal compounds for the
perovskite solar cell. All the compounds represent different variants of
the hexagonal perovskite structure (2H). Crystal structures and
perovskites, compounds of the composition A
NH , MA, FA, Gu; M = Bi, Sb; X = Cl-I (FA = formamidinium,
HC(NH , Gu = Guanidinium, C(NH ) which have, depending
3 2 9
M X ; A = alkali,
4
2
)
2
2 3
)
symmetry relations are discussed. Additionally, (CH
3
NH
consist of tetrahedral coordinated Mn and the water containing
compounds (CH NH )MnBr ∙2H O, which forms chains of edge
sharing octahedra as well as (CH NH )NiCl ∙2H O, that consist of
3
)
2
MnI
4
which
on the composition, a dimeric defect perovskite structure or a
2+
[ 5 ]
perovskite related layered structure, have been examined.
However, such bismuth based devices showed low PCE´s.[
Besides the mentioned main group halides, transition metal
halides are back into focus as well.[7] For example, the 2D layered
6 ]
3
3
3
2
3
3
3
2
dimers of octahedra, will be presented. Investigations on the crystal
structures are supported by vibrational and optical spectroscopy.
2 4
perovskites MA CuX
; X = Cl, Br have been examined in detail.[8]
But, because of the smaller ionic radii of the 3d transition metals,
a tetrahedral coordination is frequently observed, as for example
2 4
CoX
(X = Cl, Br).[9] For the same reason a widely found
in MA
structure type is the hexagonal (2H) perovskite for ABX
Introduction
3
compounds with transition metals according to the large tolerance
Since a couple of years, hybrid organic-inorganic lead halide
[10]
3
factor (t > 1). A similar effect is found for MAPbX (X = Br, I),
perovskites APbX
3
are of great interest, in particular MAPbI
3
(MA
[11]
when MA is substituted by larger cations. In contrast to the 3D
cubic perovskite, hexagonal perovskites consist of 1D chains of
=
methylammonium, CH
3
NH ). The application of MAPbI as an
3
3
[1]
excellent light harvester in solar cells has induced a strong boost
on the research of such materials. In recent years, the power
conversion energy (PCE) of such perovskite solar cells (PSC´s)
was enhanced through optimization on the cell architecture and
the composition of the absorber material, to over 20 %. For a
commercialization of such PSC´s some hurdles have to overcome.
BX
An interesting starting point of the present work are the
compounds CsNiX ; X = Cl, Br, I, as they show different colors
dependent on the halide. For X = Cl an orange, for X = Br a brown
and for X = I a black color was observed.[12] These compounds
6
octahedra sharing common faces.
3
have been intensively investigated through their 1D magnetic
properties.[13] Up to now, only a few variants of the hexagonal
On the one hand MAPbI
3
shows a significant sensitivity to
moisture,[2] on the other hand, the use of lead is problematic
because of its toxicity.
perovskites have been structurally characterized for nickel halides
; X = Cl, Br[14] the
is found in literature.
with organic cations. Beside [N(CH ) ]NiX
3 4 3
Due to these challenges, similar compounds containing other
metals are back in the focus. The most obvious way seems trying
analogous Sn(II) compounds, as it is the lighter homologue. Such
materials appear to be in principle suitable,[3] but as a result of the
redox lability, these Sn(II) compounds are not only sensitive to
[15]
crystal structure of MANiCl
3
Aim of our present work was to synthesize similar compounds
with organic cations like methylammonium (MA, H CNH ),
formamidinium (FA, HC(NH ) and guanidinium (Gu, C(NH
3
3
2
)
2
2 3
) )
and to characterizes the structural chemistry as well as the basic
optical properties.
Based on the crystal structure systematics we want to check the
potential of 3d transition metals for their application in PSC’s.
[
[
a]
b]
Institut für Anorganische und Analytische Chemie,
Albert–Ludwigs–Universität,
Albertstraße 21
D–79104 Freiburg (Germany)
Freiburger Materialforschungszentrum FMF,
Albert–Ludwigs–Universität,,
Stefan-Meier-Straße 25
Results and Discussion
D–79104 Freiburg (Germany)
3
Crystal structures of ANiX ; A = MA, FA, Gu; X = Cl, Br and
MAMnBr
3
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