U47.org Forum: Academic Dry Goods | Application of Titan

Active Topics

Memberlist

Help

The Barracks
U47.org Forum :: The Barracks

Topic: Academic Dry Goods | Application of Titan

Author

Message

<< Prev Topic | Next Topic >>

MarianJohns
Matrose
Matrose

Joined: 16 August 2022
Online Status: Offline
Posts: 5

Posted: 16 August 2022 at 04:22 \| IP Logged

Academic Dry Goods | Application of Titanium Dioxide in
Perovskite Solar Cells

Original Title Academic Dry Goods | Application of
Titanium Dioxide in Perovskite Solar Cells Click
"Material Person" above to subscribe to us Click
"Material Person" above to subscribe to us I Introduction
In recent years perovskite solar cells have rapidly
become a global research hotspot in the field of solar
cells because of their significant advantages such as low
manufacturing cost and high efficiency The theoretical
photoelectric conversion efficiency of perovskite solar
cells can reach 26% which is close to the level of
monocrystalline silicon solar cells (256%) The
photoelectric conversion efficiency of the latest
reported perovskite solar cells reaches 201% [1] which is
much higher than that of polycrystalline silicon solar
cells (18%) and has a very broad
Titanium 6Al4V
wire market application prospect In perovskite
solar cells nano-TiO2 has been widely used as electron
collection and transport materials due to its appropriate
band gap good Photoelectrochemical stability and simple
fabrication process and is usually used to fabricate
dense layers (hole blocking layers) and porous layers
(electron transport layers) [2] As one of the important
components of solar cells the crystal size particle size
and preparation method of TiO2 will significantly affect
the photovoltaic performance of solar cells Fig 1
Schematic diagram of the working principle of perovskite
solar cells [3] (A) a perovskite solar cell with a porous
TiO2 layer; (B) Planar structured perovskite solar cell
without porous layer II TiO2 dense layer Carrier
recombination can seriously affect the photoelectric
performance of solar cells and significantly reduce the
photoelectric conversion efficiency In solid-state solar
cells the hole transport layer (HTM) forms an ohmic
contact with the transparent conductive electrode (FTO)
which leads to the recombination of carriers (hole-
electron) and seriously reduces the photoelectric
conversion efficiency of the cell The dense layer between
the FTO and the porous layer can effectively avoid the
direct contact between the substrate
nickel titanium
wire and the HTM and inhibit the migration of
electrons from the FTO to the HTM The interface
recombination is related to the carrier concentration on
both sides of the interface If there is no dense layer
the direct contact between perovskite and FTO will
inevitably lead to serious electron-hole recombination;
Due to the existence of the dense layer the carrier
concentration at one side of both the FTO/TiO2 and
TiO2/perovskite interfaces is low and the dense layer can
prevent
titanium seamless
tube the reverse migration of holes so that the
electron recombination can be greatly reduced and the
device performance is improved The existence of the dense
layer helps to improve the electron collection efficiency
thereby improving the photoelectric performance of the
cell The dense layer with excellent performance needs to
meet the following three requirements [4] (1) good
optical performance so as not to affect the absorption of
visible light by the perovskite layer; (2) the energy
band structure is matched with the electrodes sensitizing
materials etc and the purpose of efficiently and
selectively injecting the required carriers and blocking
another carrier is achieved through the appropriate
energy band structure between the functional layers of
the cell; (3) that thickness of the dense lay film is
appropriate TiO2 is the most commonly used dense layer
material but its electron mobility is low so n-type metal
oxide semiconductors with good optical properties high
carrier mobility and band matching such as SnO2 and ZnO
are also used to make dense layers of perovskite solar
cells Expand the full text Fig 2 Schematic diagram of a
typical perovskite solar cell structure [5] (A) Meso-
structured perovskite solar cells; (B) Planar
heterostructure perovskite solar cells 21 Preparation
method of dense layer TiO2 exists in nature in three
forms rutile anatase and brookite The rutile phase is the
most stable of
titanium round
bar the three When the temperature is higher than
650 ° C the anatase phase will begin to transform into
the rutile phase while brookite is only an intermediate
phase in the crystallization process of anatase and
generally only exists stably in minerals with impurities
TiO2 anatase phase crystals are the most used in
perovskite solar cell research

Table 1 Performance comparison of typical perovskite
solar cells with TiO2 as the electron transport layer [6]
The preparation methods of dense layer mainly include
spin coating spray pyrolysis atomic layer deposition
microwave sintering magnetron sputtering etc Generally
spin coating and spray pyrolysis are simple and easy to
operate Dense layers of other metal oxides can be
prepared in essentially the same way However both spin-
coating and spray pyrolysis require high temperature
annealing at 500 ° C to transform anatase TiO2 into
anatase phase and improve its ability to transport
electrons which limits the application of anatase TiO2 on
flexible substrates Moreover the thermal contraction
during the phase transformation process will leave holes
on the surface of the film making the connectivity
between particles worse [2] Therefore the preparation of
dense anatase TiO2 at low temperature has become one of
the important research directions of perovskite solar
cells The reported low-temperature fabrication methods of
TiO2 dense layers include atomic layer deposition (ALD
200 ° C) spin-coating of anatase TiO2 particles (< 150
° C) low temperature plasma
titanium tubing
price enhanced atomic layer deposition (PEALD 80
° C) and low temperature chemical bath deposition (70
℃) 22 Interface optimization of the dense layer On the
basis of perovskite thin film materials with regular
morphology the device performance mainly depends on the
reasonable design of device structure and the matching of
interface energy levels In addition the behavior of
carrier migration and recombination at the interface
between layers is not only related to the aggregation
morphology of the active layer but also depends on the
size of the interface barrier between the electron
transport layer or the hole transport layer and the
electrode In order to obtain more efficient and stable
solar cells the contact interface is usually optimized
such as passivation of the surface of titanium dioxide
The photoelectric conversion efficiency of the solar cell
can be improved by depositing a thin layer of Sb2S3
Cs2CO3 (2 nm) and other materials on the TiO2 dense layer
as a common dense layer The TiO2 dense layer was modified
by C60-SAM TiCl4 and UV (O3) treatment which can improve
the contact between the dense layer and the perovskite
layer promote charge transport and reduce electron
recombination and improve the conversion efficiency The
graphene nanosheet/nano titanium dioxide composite
material is used as an electron transmission layer and
the characteristics of high conductivity proper work
function (between FTO and TiO2) and the like of graphene
are utilized to provide a high-speed channel for electron
transmission and collection so that the electron
transmission performance of the material is improved the
series resistance of the battery is obviously reduced And
the short-circuit current and the fill factor are
obviously improved There is a Schottky barrier at the
interface between transparent conductive oxide (ITO or
FTO) and electron transport layer TiO2 which will destroy
the performance of the device when the barrier is too
large The electron collection efficiency can be improved
by adjusting the work function of the metal to be close
to the Fermi level of TiO2 The Y-doped compact TiO2
material is used as an electron transport layer and the
surface of the ITO conductive glass is modified so that
the interface potential barrier between the electron
transport layer/transparent conductive oxide can be
reduced the electron transport is facilitated and the
photoelectric conversion efficiency of the solar cell is
improved In addition Al doping Zr doping and Nb doping
can improve the performance of TiO2 dense layer 23
Thickness of dense layer Increasing the thickness of the
dense layer can improve the coverage reduce the number of
holes in the dense layer and reduce the recombination
rate At the same time the resistance of the dense layer
itself will also affect the performance of the battery
The dense layer resistance of the material was determined
to be related to the dense layer thickness The increase
of thickness will lead to the increase of dense layer
resistance affect the series resistance of the whole cell
and reduce the efficiency of the cell Therefore an
efficient dense layer usually needs to reduce the
thickness as much as possible on the premise of meeting
the high coverage If there is no dense layer or the
thickness of the dense layer is too thin the FTO can not
be completely covered by titanium dioxide resulting in
direct contact between the perovskite film and FTO which
leads to the increase of electron-hole recombination rate
on the surface of FTO and serious current leakage

A dense layer that is too thin also affects the coverage
of the perovskite sensitizing layer; if the dense layer
is too thick electrons are recombined before being
transported from the perovskite layer to the conductive
substrate At present the optimized thickness of the dense
layer is generally 30 to 100 nm III TiO2 porous layer At
present most PSCs utilize submicron-thick porous metal
oxide films to adsorb perovskite which are called porous
layers Similar to the dense layer materials
semiconductors with matching energy level structure and
high carrier mobility can be used as electron (or hole)
transport layer materials with mesoscopic structure The
electron transport layer represented by TiO2 mesoporous
nanoparticles has been widely used in perovskite
batteries Because perovskite materials also have good
electron transport properties high band gap oxides such
as Al2O3 and ZrO2 can also be used to make porous layers
of perovskite solar cells Mesoporous TiO2 has a large
specific surface area which is convenient for the maximum
adsorption of perovskite materials and provides a space
for the oriented growth of perovskite films
titanium filler
rod In addition the mesoporous TiO2 can be fully
contacted with the perovskite material to ensure maximum
photogenerated charge separation and charge injection 31
Particle Size Pore Size and Film Thickness The thickness
of the porous layer has a crucial effect on the
perovskite film and its presence contributes to the
complete conversion of PbI2 to perovskite It is reported
that the size of TiO2 particles not only affects the
implantation of precursors and the contact between
perovskite crystals and TiO2 but also affects the charge
transport kinetics at the perovskite/TiO2 interface With
the increase of the thickness of the porous layer the
dark current in the TiO2 porous material will also
increase linearly resulting in the decrease of electron
concentration and voltage When the perovskite completely
fills the pores of TiO2 the direct contact between TiO2
and the hole transport layer can be effectively avoided
and the electron recombination is reduced The large pore
size in porous TiO2 is also more conducive to the filling
of perovskite particles In fact TiO2 particle size pore
size and film thickness do not have a linear relationship
with the photoelectric performance of the cell and these
parameters are mutually influenced and interacted This
factor is also one of the reasons for the unstable
efficiency of perovskite solar cells and only by
exploring their optimal conditions can the whole
photovoltaic device be further optimized 32 Crystal form
and morphology Due to the better electron transport
properties of anatase phase titanium dioxide it is often
used as electron transport material in photovoltaic
devices and a few researchers use rutile phase titanium
dioxide In addition to the crystal form of titanium
dioxide the morphology has an important impact on the
light absorption electron transport and electron capture
of the cell Titanium dioxide nanosheets can improve the
contact between perovskite and porous layer and titanium
dioxide nanotubes with less grain boundaries can
significantly improve the light absorption and electron
collection efficiency The porous nano-TiO2 fibers with
different diameters and lengths were prepared by
electrospinning The results showed that the fibers with
too small diameter were discontinuously distributed and
the fibers with too large diameter were arranged too
closely which hindered the adsorption of perovskite Fig 3
Structure diagram of different nanorod lengths [2] 33
Modification of porous TiO2 Surface treatment and doping
are effective means to modify titanium dioxide materials
and the properties of materials can be significantly
improved by reasonable control of conditions The Nb-doped
rutile-type titanium dioxide nanorods are used as
photoanodes so that the photoelectric conversion
efficiency of the solar cell is remarkably improved; MgO
is used as a compact layer and the porous TiO2 with a
small part of MgO adsorbed is used as a skeleton layer so
that the effective injection of electrons is facilitated
and the recombination of carriers is reduced The
interfacial contact between TiO _ 2 and CH _ 3NH _ 3PbX _
3 plays an important role in determining the growth of
perovskite crystal and the charge separation Although
TiO2 has a suitable energy level and generally acts as an
electron transport layer to block holes it has poor
conductivity which results in additional ohmic losses and
an undesirable space charge distribution The Y-doped
titanium dioxide is used as a porous layer which can not
only improve the morphology of the perovskite layer but
also enhance the adsorption of the perovskite layer and
the electron transport performance in the battery Al2O3
ZnO and ZnSO4 are less used in perovskite solar cells
because their comprehensive properties are far inferior
to those of TiO2

34 Stability In terms of stability the device performance
of perovskite solar cells based on mesoporous TiO2
structure decays rapidly under UV irradiation due to the
desorption of oxygen on the surface of TiO2 itself There
are many oxygen vacancies or defects on the surface of
TiO2 and these deep level defects will adsorb oxygen
radicals in the air and this adsorption is unstable TiO2
generates electron-hole pairs under the excitation of
ultraviolet light The holes in the valence band react
with oxygen radicals and release oxygen molecules thus
forming a free electron and a positively charged oxygen
vacancy in the conduction band The free electron quickly
recombines with the holes in HTM However the energy level
of the defect state caused by the oxygen vacancy is
relatively deep and when the photogenerated electrons are
transferred to it it is difficult to jump to the
conduction band again so they can only recombine with the
internal holes resulting in a decrease in short-circuit
current and a decline in cell performance IV Outlook
Currently TiO2 is the most widely used electron transport
layer material in perovskite solar cells In order to
further improve the photoelectric conversion efficiency
of solar cells the preparation of nano-TiO2 with high
specific surface area low defects and appropriate pore
size is helpful to adsorb more photosensitizers thus
producing greater photocurrent and reducing defects
Doping and surface modification of TiO2 are helpful to
improve its performance References [1] Tan H et al
Efficient and stable solution-processed planar perovskite
solar cells via contact passivation Science 2017 [2] Que
Yaping Weng Jian Hu Linhua et al Application of TiO 2 in
Perovskite Solar Cell [J] Progress in chemistry 2016
28(1) 40-50 [3] Jung H S Park N G Perovskite solar cells
from materials to devices[J] small 2015 11(1) 10-25 [4]
Wang Weiqi Zheng Huifeng Lu Guanhong et al Research
Progress of Nanometer Metal Oxides in Perovskite Battery
[J] Journal of Inorganic Materials 2016 31(9)：897-907
[5] Bai Yubing Wang Qiuying Lv Ruitao et al Progress in
Perovskite Solar Cell [J] Science Bulletin 2016 61 489-
500 [6] Yang Ying Gao Jing Cui Jiarui et al Progress in
Perovskite Solar Cell [J] Journal of Inorganic Materials
2015 30(11) 1131-1138 Material People's Network focuses
on tracking the progress of science and technology and
industry in the field of materials It brings together
master and doctoral students from major universities
front-line scientific researchers and industry
practitioners If you are interested in tracking the
progress of science and technology in the field of
materials interpreting high-level articles or commenting
on the industry click "Read the original" below to enter
Material People's Network and sign up to join the
editorial department The material person net to each big
team invites the manuscript sincerely the research group
newest achievement the direction summary the team
interview the experimental skill and so on may contribute
once the outstanding manuscript is hired we will offer
the remuneration please contact Email
tougao@cailiaorencom or QQ 97482208
Material Man Long press the QR code to subscribe to
materials to learn more about technology services
Cooperative contact Test Valley Material People's One-
stop Material Analysis and Testing Solution Platform Has
Been Revised and Launched! （ Test Business
XRD/TEM/SEM/DSC/AFM/Mechanical Test/Thermal
Analysis/PPMS/IR/Particle Size Analysis Technical
services Thesis polishing/Thesis drawing/Theoretical
calculation/EBSD data analysis/MS use guidance/TEM
operation guidance Business cooperation 15120014412
Mailbox kefu@cailiaorencom Material people are here
waiting for you to return to Sohu to see more Responsible
Editor
yunchtitanium.com

If you wish to post a reply to this topic you must first login
If you are not already registered you must first register

Printable version

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum