chemists have figured out
different perovskite materials
ordered vacancies halide ions.
the carbon coating that is
diffusion barrier for halide ions.
in the journal Advanced
solar cells are cheap, easy to obtain and effective: a battery of pure perovskites already show
25.2 per cent,
tandems silicon-perovskite — 29.1 per cent.
such solar cells today
entered the market, they would have made
serious competition for the current leaders
solar elements on the basis of the net
However, until commercialization
under the action of sunlight, with
the presence of water and oxygen. On
the chemical mechanism of this process
still very little is known:
the final product
always been a halide
here is the interim
process to track
failed. In addition
it was unclear whether
General mechanism of degradation of all
perovskite materials or each
the connection degrades on its own.
under the leadership of the pan
to identify the mechanism of degradation of perovskite
reproduced for several different
electron diffraction in selected area
— that is, the irradiated material electronic
the beam of
transmission electron microscope
watched as under
the action of this beam
the crystal lattice of the material.
the study was a thin film of two
perovskite materials — MAPbI3
conducting substrate covered with oxide
titanium, that is lower
the halide ions and the formation of
the intermediate reaction product, which
when further degradation of the turns
positions in the lattice)
ordered, that is, form a
the crystal structure, repetitive
with some regularity and creating
thus a new structure with others
the period of rotation. This
the superstructure the authors observed for
materials, which is pretty remarkable,
after initially crystalline
the structure of these materials is different —
mechanisms of degradation were
other materials with the structure
perovskite — CsPbBr3
you can talk about the existence of universal
mechanism of degradation of these compounds.
of degradation the authors proposed to use
carbon coating thickness
6-10 nanometers, which
caused by the method of precision etching.
calculations show that a layer
thin to affect the scattering
electrons, but it can
diffusion barrier for halide ions
preventing their loss.
the hypothesis is confirmed experimentally:
apply a carbon coating only
the one hand,
that stabilization does not occur, because
the halide ions can leave the grid
now, if coating both sides
the stability of perovskite material
increases: in particular covered
carbon on both sides of the sample MAPbI3
to tolerate a dose of
exposure ten times greater than
the same sample without coating.
coating on the migration of halide ions
last month another
a group of chemists.
two-dimensional perovskite heterostructure
a layer of a hard polymer with aromatic
fragments, which let
the adjustment of the crystal lattice on the
the border of the two perovskites and much
slowed migration of halide ions.