Chemists have stopped the migration of ions in the perovskite

Chemists for the first time managed to obtain two-dimensional
rectangular
film from two different perovskite
materials.
The Central region
is
from one of perovskite, and the frame width of one micron from
the other, the border
between them is very clear, with almost atomic
resolution.
For
also
below
to stabilize the boundary between two materials scientists
slowed down the migration of halide ions
in perovskite, with
layer
bethovensymphony.
Results
research published
in the journal
Nature.

Semiconductor
lead-halogenide materials with
structure of perovskite

the rising star of modern electronics.
These
the materials are cheap, easy to obtain
(you can
to mortar methods)
and at the same time
combine
several useful properties:
high
the absorption coefficients,
tolerance
to
defects and
large the life time of charge carrier.
Efficiency
perovskite
solar
elements
just
ten
years rose from 3.8 to 25.2 percent,
also
on their basis is made luminous
light-emitting
diodes
and
the photodetectors.
In
now scientists
working to improve
the stability of perovskites as she
insufficient to yield
on the market.

Crystal
the perovskite lattice
c
formula
APbX3
(Pb
— lead,
X
— halide ion,
usually iodide or bromide)
is
of the interconnected vertices of the octahedra
PbX6, between
layers which are large A-cations:
cesium
or organic
derivatives of ammonium
matrimony or formamidine.
Recently
scientists have learned how to isolated
layers of this material —
so
called two-dimensional or 2D perovskites
(here
you can draw an analogy with layered
graphite and its 2D-shape
— graphene). In
2D perovskite
part
A-cations
replaced by more
surround the cations (most often it is also
derivatives
ammonium
with long branched
“tails”),
which
forming a separating layer in
the resulting material has the structure
sandwich — a layer of octahedrons
PbX6
you’ll
between two layers of organic cations.
TRANSPORTNYE
properties (lifetime and length of run
have nositelya charge), and
also the luminescence quantum yield from
two-dimensional
perovskites
even better than the standard three-dimensional
so
these materials are very promising for
creation of light and the other
optoelectronics.

Two-dimensional
material can be collected from several
perovskites of different composition. Such
double
or triple
materials
(heterostructures)
share
on the vertical
and
lateralline.
In
vertical geterostrukturakh alternate
layers of different composition, for example,
first
the layer may consist of lead-ideny
octahedra PbI6,
second
derived from
ammonium
and the third
from
lead-bromidic
octahedra PbBr6.
In
lateral heterostructures
the transition
from one part to another occurs
in
plane of one layer —
but they must be clearly
separated from each other, otherwise it will not
heterostructure, and just mixed
material. Combining
different compositions of perovskites can
to obtain material with the desired optical
and transport characteristics
so
such structures pose to scientists
and engineers special interest. However,
in practice
with
their
synthesis while
that there are difficulties —
and
especially
this applies to lateral structures. Case
again
insufficient
stability
perovskites: for example, they occur
the migration process halide ions from
one area to another, resulting in
the boundaries of the two regions formed
a transitional zone with a mixed composition.

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