Nanoparticles of tin tin saved the perovskites from defects

Japanese
chemists for the first time
synthesized
film tin
perovskites
without impurities
chetyrehjadernogo tin. For
this source solutions for the application
films added
nanoparticles
metal
tin.
Received
solar cells demonstrated
efficiency of 11.5 percent. Results
research published
in the journal Nature
Communications.

Perovskite
semiconductor
materials
on the basis of the halides of tin — good
alternative to toxic lead
the perovskites for
use in solar cells,
light-emitting diodes and photosensors.
Tin
perovskites have begun to actively explore
recently, therefore, the characteristics of
devices
their basis is markedly
lower than traditional counterparts:
for example, a record
the efficiency of solar
item
on the basis of
tin perovskite
is
12.4 percent (for traditional
lead
perovskite — 25.2%). There are several reasons: for example,
tin perovskite has not yet been found
ideal transport
materials — the so-called two layer
semiconductor, which are located
in the perovskite solar cell between
the active layer and the electrodes (one of
these layers transmit only the electrons
and the other only holes). In addition
also
tin
perovskites kristallizuetsya faster
than lead,
so to
film high
quality of them more difficult.

However, the main reason for the low
the efficiency of devices based on
tin perovskites —
the formation of
defects of tin in the oxidation state +4.
Film of tin perovskites AP3
(where
A large single-shot methylammonium,
formamidine or cesium, X
— the iodide anion
or bromide anion)
get
from solutions of the respective halide
tin SnX2.
In
the composition
such compounds divalent
tin Sn2+ may
to oxidize to the tetravalent
Sn4+.
Especially quickly these processes occur
in solutions of the halides of tin SnI2
and SnBr2

even
if the solutions are prepared and stored in inert
the atmosphere, enough
traces of oxygen in the solvent to
part of the tin went into a state Sn4+.
In
ready
perovskite
the film
tetravalent
tin forms the defects,
increase
share
nonradiative
recombinationof carriers
charge, as a result, the efficiency
a solar cell or diode based
such a film is reduced.

Scientists
from
Kyoto University under
leadership Akamai Atsushi (Atsushi Wakamiya) has proposed to clean
source
materials
for tin perovskites with
using
received
in
situ nanoparticles
metal
tin.
For
was based on the mixed perovskite
composition
FA0.75MA0.25SnI3
for its synthesis we mixed solutions
iodide of tin
SnI2,
iodide formamidine FAI,
and
iodide of methylamine MAI
and
apply the mixture
on
rotating a substrate by a method of spin-coating.
In addition
in the solution of the original compounds
added
small
the number
fluoride
tin SnF2

in previous works it was shownthat
this salt limits the growth rate
perovskite films and improves their
quality.

The authors
suggested
to convert part of the Sn2+
fluoride of tin nanoparticles, tin
Sn0,
restoring
them using a derived
dihydropyrazine
(TM-DHP).
Received
the nanoparticles then
restore
Sn4+,
entering
with him in the reaction of nonproportionally.

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