Description:FIELD OF INVENTION
[001] The present disclosure broadly relates to the field of perovskite ink
composition and perovskite solar cells. It further relates to a method of preparing
the perovskite ink composition and solar cells.
5 BACKGROUND OF THE INVENTION
[002] Perovskite solar cells are considered a promising next-generation
photovoltaic technology because of their low cost and ease of fabrication. This
technology uses the perovskite crystal structure as the light-absorbing material to
convert sunlight into electricity. A key advantage of the technology is its printability
10 using precursors or inks.
[003] The synthesis of perovskite solar cells has been an active field of research for
more than 15 years. One of the most common ways to synthesize perovskite thin
films is through wet processing, e.g., spin-coating, slot-die coating, doctor blading,
spray-coating, etc. Wet processing requires the preparation of a liquid precursor
15 (i.e., "ink") that can be used to cast films. The cast films are polycrystalline, and
obtaining a large grain size is critical to high performance. Therefore, there exists a
need for technologies to obtain high-quality perovskite films with larger grain sizes
and improved optoelectronic properties.
20 SUMMARY OF INVENTION
[004] In an aspect of the present disclosure, there is provided a perovskite ink
comprising: a perovskite powder; and a solvent in which the perovskite powder is
dissolved, wherein the perovskite ink has a viscosity in a range of 1 mPa·s and 10
mPa·s, and wherein the perovskite ink has a bimodal size distribution comprising a
25 first population of particles having sizes in a range of about 1 nm to about 20 nm
and a second population of particles having sizes in a range of about 100 nm to
about 30000 nm.
[005] In an aspect of the present disclosure, there is provided a method for preparing
the perovskite ink as disclosed herein, the method comprising: (a) dissolving
2
perovskite precursors in a first solvent to form a solution; (b) heating the solution
to precipitate the perovskite powder; (c) filtering the perovskite powder; and (d)
redissolving the perovskite powder in a second solvent to form the perovskite ink.
[006] In an aspect of the present disclosure, there is provided a perovskite film
5 prepared using the perovskite ink as disclosed herein.
[007] In another aspect of the present disclosure, there is provided a perovskite solar
cell, comprising: a substrate; and the perovskite film, as disclosed herein, deposited
on the substrate.
[008] In another aspect of the present disclosure, there is provided a method of
10 fabricating the perovskite solar cell, the method comprising: (a) coating an
anode/cathode layer on substrate; (b) coating a hole/electron transport layer on a
substrate to obtained a hole/electron transport layer coated substrate; (c) depositing
the perovskite ink as claimed in claim 1 on the hole/electron transport layer coated
substrate to form a perovskite film; (d) subjecting the perovskite film to heat
15 treatment; and (e) coating electron/hole transport layer, followed by cathode/anode
layer over the perovskite film.
[009] These and other features, aspects, and advantages of the present subject
matter will be better understood with reference to the following description. This
summary is provided to introduce a selection of concepts in a simplified form. This
20 summary is not intended to identify key features or essential features of the claimed
subject matter, nor is it intended to be used to limit the scope of the claimed subject
matter.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[0010] The following drawings form a part of the present specification and are
25 included to further illustrate aspects of the present disclosure. The disclosure may
be better understood by reference to the drawings in combination with the detailed
description of the specific embodiments presented herein.
[0011] Figs. 1(a), 1(b) and 1(c) depicts characterization data for perovskite film,
wherein 1(a) depicts thin-film morphology, 1(b) depicts thin film grain size
30 distribution, and 1(c) depicts thin-film cross-section for perovskite films (SP film-
3
Top and PP film-Below) obtained using the perovskite inks prepared by salt
processed (SP) and powder processed (PP) routes, in accordance with the
embodiments herein.
[0012] Fig. 2(a) depicts the XRD spectrum for perovskite films obtained using PP
5 and SP processed perovskite inks, in accordance with the embodiments herein.
[0013] Fig. 2(b) depicts the absorption coefficient of perovskite films obtained
using PP and SP processed perovskite inks, in accordance with the embodiments
herein.
[0014] Fig. 3 depicts viscosity for PP and SP processed perovskite ink, in
10 accordance with the embodiments herein.
[0015] Figs. 4(a)-4(b) depicts particle size distribution for PP and SP processed
perovskite ink, in accordance with the embodiments herein.
[0016] Fig. 5 is a representation depicting the architecture for solar cell fabrication
using perovskite inks, in accordance with the embodiments herein.
15 [0017] Fig. 6 depicts current density-voltage characteristics for solar cells produced
using PP and SP processed perovskite ink, in accordance with the embodiments
herein.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Those skilled in the art will be aware that the present disclosure is subject
20 to variations and modifications other than those specifically described. It is to be
understood that the present disclosure includes all such variations and
modifications. The disclosure also includes all such steps, features, compositions,
and compounds referred to or indicated in this specification, individually or
collectively, and any and all combinations of any or more of such steps or features.
25 Definitions
[0019] For convenience, before further description of the present disclosure, certain
terms employed in the specification, and examples are delineated here. These
definitions should be read in the light of the remainder of the disclosure and
understood as by a person of skill in the art. The terms used herein have the
30 meanings recognized and known to those of skill in the art, however, for
4
convenience and completeness, particular terms and their meanings are set forth
below.
[0020] The articles “a”, “an” and “the” are used to refer to one or to more than one
(i.e., to at least one) of the grammatical object of the article.
5 [0021] The terms “comprise” and “comprising” are used in the inclusive, open
sense, meaning that additional elements may be included. It is not intended to be
construed as “consists of only”.
[0022] Throughout this specification, unless the context requires otherwise the
word “comprise”, and variations such as “comprises” and “comprising”, will be
10 understood to imply the inclusion of a stated element or step or group of element or
steps but not the exclusion of any other element or step or group of element or steps.
[0023] The term “including” is used to mean “including but not limited to”.
“Including” and “including but not limited to” are used interchangeably.
[0024] The term "perovskite", as used herein, refers to a class of materials having
15 a crystal structure with the general formula ABX3, where “A” is at least one cation,
“B” is at least one cation, and “X” is at least one anion. In some aspects, perovskite
may include organic-inorganic hybrid perovskites, where the “A” cation may be an
organic cation such as methylammonium (MA+), formamidinium (FA+), or
combinations thereof, the B cation may be a metal cation such as lead (Pb2+), tin
20 (Sn2+), or combinations thereof; and the X anion may be a halide such as iodide (I-
), bromide (Br-), chloride (Cl-), or combinations thereof. In some cases, perovskite
materials may exhibit semiconducting properties and may be suitable for use in
optoelectronic applications such as solar cells, light-emitting diodes, and
photodetectors. In some aspects, the perovskite may include mixed cation
25 compositions such as (MAxAA1-x)PbI3, wherein MA represents methylammonium,
and AA represents an alternative organic cation, and x is a value between 0.5 and
1. In an embodiment, “x” represents molar fraction of methylammonium cations.
In an embodiment, “x” is a value between 0.8 and 1, preferably 0.9. In other aspects,
the perovskite may include mixed cation and mixed halide compositions such as
30 Cs0.05(FAxMA1-x)Pb(I0.9Br0.3)3, wherein Cs represents Cesium, FA represents
Formamidinium, MA represents Methylammonium.
5
[0025] Accordingly, the term “perovskite powder" refers to a particulate form of
perovskite comprising discrete particles or grains of perovskite crystals.”
[0026] The term "solvent", as used herein, refers to a liquid medium capable of
dissolving, dispersing, or suspending other substances to form a homogeneous
5 solution or mixture. In some aspects, the solvent may facilitate the dissolution of
perovskite precursors or perovskite to form ink compositions or precursor solutions.
The solvent may be selected based on its ability to dissolve the desired materials,
its volatility characteristics, and its compatibility with processing conditions. In
some embodiments, the solvent may be selected from dimethyl formamide (DMF),
10 dimethyl sulfoxide (DMSO), γ-butyrolactone, acetonitrile, or combinations thereof.
[0027] The term "antisolvent", as used herein, refers to a liquid that has poor
solubility for a particular solute. In some aspects, when an antisolvent is added to a
solution, it may reduce the solubility of the solute and promote precipitation or
crystallization of the solute. The antisolvent may be used to control nucleation and
15 crystal growth processes during film formation. For example, in perovskite
preparation or processing, chlorobenzene and diethyl ether may be used as
antisolvents during spin-coating to induce rapid crystallization of perovskite from
DMF or DMSO-based precursor solutions.
[0028] The term "particle size distribution" or "particle distribution" or “size
20 distribution", as used herein, refers to a statistical distribution that describes the
relative amounts of particles present according to their physical dimensions in a
sample. In some aspects, particle size distribution may be represented as a plot or
histogram showing the frequency, volume, or intensity of particles as a function of
their size. The distribution may be characterized by parameters such as mean size,
25 median size, mode size, and distribution width or polydispersity. In some cases,
particle size distribution may be measured using techniques such as dynamic light
scattering, laser diffraction, or image analysis of microscopy data. The particle size
distribution may be monomodal (showing a single peak), bimodal (showing two
distinct peaks), or multimodal (showing multiple peaks), and may influence
30 properties such as solution viscosity, film formation characteristics, etc.
6
[0029] The term "bimodal size distribution", as used herein, refers to a particle size
distribution characterized by the presence of two distinct populations or peaks of
particles having different size ranges. In some aspects, a bimodal size distribution
may exhibit two separate maxima or modes when the particle size data is plotted as
5 a frequency distribution or intensity distribution versus particle size. The two
populations may be separated by a region of lower particle concentration or may
partially overlap while still maintaining distinct peaks.
[0030] The term "viscosity", as used herein, refers to a measure of a fluid's
resistance to flow or deformation under applied stress. In some aspects, viscosity
10 may quantify the internal friction within a fluid that opposes the relative motion
between adjacent layers of the fluid. Viscosity may be expressed in units such as
pascal-seconds (Pa·s), millipascal-seconds (mPa·s), or centipoise (cP). In some
cases, higher viscosity values may indicate greater resistance to flow, while lower
viscosity values may indicate easier flow characteristics.
15 [0031] The term "perovskite film", as used herein, refers to a thin layer or coating
of perovskite or perovskite ink deposited on a substrate. In some aspects, the
perovskite film may be formed through various deposition techniques such as spin-
coating, blade-coating, slot-die coating, spray-coating, or vapor deposition
methods. The perovskite film may have a thickness ranging from nanometers to
20 micrometers and may exhibit crystalline or polycrystalline structure with varying
grain sizes and morphologies. In some cases, the perovskite film may serve as a
photoactive layer in optoelectronic devices such as solar cells, light-emitting
diodes, or photodetectors, where it may absorb light and generate charge carriers
for device operation.
25 [0032] The term "solar cell", as used herein, refers to a photovoltaic device that
converts solar energy or light energy into electrical energy through the photovoltaic
effect. In some aspects, a solar cell may comprise one or more layers of photoactive
materials that absorb photons and generate electron-hole pairs, which are then
separated and collected to produce an electric current. The solar cell may include
30 various functional layers such as electron transport layers, hole transport layers, and
electrodes to facilitate charge extraction and collection. In some cases, solar cells
7
are fabricated using perovskite materials and may be assembled into solar panels or
photovoltaic modules for power generation applications.
[0033] Accordingly, the term “perovskite solar cell” refers to a solar cell that is
fabricated using perovskite or perovskite material as the photoactive material to
5 absorb light and generate charge carriers for electrical energy conversion.
[0034] The term "polydispersity", as used herein, refers to the degree of non-
uniformity in the size distribution of particles within a sample. For example, a
sample with low polydispersity may have particles that are relatively uniform in
size, while a sample with high polydispersity may contain particles with a wide
10 range of sizes. In some aspects, polydispersity may be quantified using parameters
such as the polydispersity index or standard deviation of the size distribution, and
may influence properties such as solution behavior, film formation characteristics,
etc.
Perovskite ink
15 [0035] Embodiments herein provide a perovskite ink. In an embodiment, the
perovskite ink as disclosed herein is for preparing perovskite films and solar cells.
In an embodiment, a perovskite ink may comprise a perovskite powder dissolved
in a solvent to form a homogeneous solution.
[0036] The perovskite powder, according to embodiments herein, may comprise a
20 precursor, such as lead iodide (PbI2), methylammonium iodide (MAI),
acetamidinium iodide (AAI), formamidinium iodide (FAI), or their combinations;
or may comprise pre-formed perovskite having compositions such as
methylammonium lead iodide (MAPbI3), formamidinium lead iodide (FAPbI3),
mixed cation perovskites, or mixed cation mixed halide perovskites. In an
25 embodiment, the perovskite powder comprises a perovskite compound selected
from (MAxAA1-x)PbI3, FAPbI3, Cs0.05(FAxMA1-x)Pb(I0.9Br0.3)3, or MAPbI3, where
MA is methylammonium, AA is acetamidinium, FA is formamidinium, and x is a
value between 0.5 and 1. In an embodiment, x is selected from 0.7, 0.8, or 0.9. In
another embodiment, the perovskite powder is obtained from precursors:
30 methylammonium iodide (MAI), acetamidinium iodide (AAI), and lead iodide
(PbI2). In an embodiment, the perovskite powder is (MA0.9AA0.1)PbI3. In another
8
embodiment, the perovskite powder is obtained from precursors: methylammonium
iodide (MAI), acetamidinium iodide (AAI), and lead iodide (PbI2), wherein the
precursors methylammonium iodide (MAI), acetamidinium iodide (AAI), and lead
iodide (PbI2), are in a weight ratio range of 0.7:0.4:0.8 to 0.95:0.05:1.2, preferably
5 0.8-0.95:0.2-0.09:0.9-1.2, more preferably 0.9:0.1:1.
[0037] The perovskite powder may be present in the perovskite ink at a
concentration in the range of 0.5 M to about 2.0 M, preferably 0.8 M to about 1.5
M. Accordingly, in an embodiment, there is provided a perovskite ink, wherein the
perovskite powder is in a concentration range of 0.5 to 2 M, preferably 0.8 M to
10 about 1.5 M. In an embodiment, there is provided a perovskite ink, wherein the
perovskite powder is in a concentration of 1.2 M.
[0038] The solvent in the perovskite ink, according to embodiments herein, may be
selected from polar aprotic solvents including, but not limited to, acetonitrile,
dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL),
15 N-methyl-2-pyrrolidone (NMP), or combinations thereof. Accordingly, in some
embodiments, there is provided a perovskite ink, wherein the solvent is selected
from acetonitrile, dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), γ-
butyrolactone (GBL), N-methyl-2-pyrrolidone (NMP), or combinations thereof. In
an embodiment, the solvent comprises DMF and DMSO, preferably in a volume
20 ratio in a range of 2: 1 to 10:1, preferably 3: 1 to 10:1, more preferably 7: 1 to 10:1.
In a preferred embodiment, the solvent comprises a mixture of DMF and DMSO in
a volume ratio of 9:1.
[0039] In an embodiment, there is provided a perovskite ink comprising a
perovskite powder; and a solvent, wherein the perovskite ink has a viscosity in a
25 range of 1 mPa·s and 10 mPa·s, preferably 3.5 mPa·s to 5.0 mPa·s, more preferably
3.5 mPa·s to about 4.5 mPa·s, 3.5 mPa·s to about 4.4 mPa·s, or 3.5 mPa·s to about
4.3 mPa·s.
[0040] The perovskite ink has a bimodal size distribution with particles having size
in the range of one to tens of nanometers and hundreds to tens of thousands of
30 nanometers.
9
[0041] In an embodiment, there is provide a perovskite ink comprising a perovskite
powder; and a solvent, wherein the perovskite ink has a bimodal size distribution
comprising a first population of particles having sizes in a range of about 1 nm to
about 20 nm, preferably 1 nm to about 10 nm, more preferably 1 nm to about 6 nm
5 and a second population of particles having sizes in a range of about 100 nm to
about 30000 nm, preferably 200 nm to about 10000 nm, more preferably 400 nm to
about 10000 nm.
[0042] In an embodiment, there is provide a perovskite ink comprising a perovskite
powder; and a solvent in which the perovskite powder is dissolved, wherein the
10 perovskite ink has a viscosity in a range of 1 mPa·s and 10 mPa·s, and wherein the
perovskite ink has or exhibits a bimodal size distribution comprising a first
population of particles having sizes in a range of about 1 nm to about 20 nm,
preferably 1 nm to about 10 nm, more preferably 1 nm to about 6 nm and a second
population of particles having sizes in a range of about 100 nm to about 30000 nm,
15 preferably 200 nm to about 10000 nm, more preferably 400 nm to about 10000 nm.
[0043] In an embodiment, there is provide a perovskite ink comprising a perovskite
powder; and a solvent in which the perovskite powder is dissolved, wherein the
perovskite ink has a viscosity in a range of 1 mPa·s and 10 mPa·s, as measured
using a rheometer at room temperature (at about 20 °C to 30 °C), and wherein the
20 perovskite ink has or exhibits a bimodal size distribution comprising a first
population of particles having sizes in a range of about 1 nm to about 20 nm,
preferably 1 nm to about 10 nm, more preferably 1 nm to about 6 nm and a second
population of particles having sizes in a range of about 100 nm to about 30000 nm,
preferably 200 nm to about 10000 nm, more preferably 400 nm to about 10000 nm,
25 as measured using dynamic light scattering.
Perovskite film and solar cell
[0044] Embodiments herein provide a perovskite film. The perovskite film,
according to embodiments herein, are prepared using the perovskite ink as disclosed
30 herein. In an embodiment, there is provided a perovskite film prepared using the
perovskite ink. In some embodiments, the perovskite film may comprise the
10
perovskite ink deposited as a thin layer on a substrate. The perovskite may have a
crystalline structure with grain sizes ranging from about 100 nm to about 700 nm,
preferably 100 nm to 500 nm, or more preferably 200 nm to 500 nm.
[0045] In some embodiments, the perovskite film may be formed through solution
5 processing techniques such as spin-coating, where a perovskite precursor solution
is applied to the substrate and subjected to antisolvent treatment to promote rapid
crystallization. The perovskite film may have a thickness ranging from about 100
nm to about 1000 nm, preferably from 200 nm to 600 nm, or more preferably 200
nm to 500 nm. Further, in some embodiments, the perovskite film may exhibit
10 uniform coverage with minimal pinholes or defects. In some embodiments, the
perovskite film may be annealed at elevated temperatures to improve crystallinity
and remove residual solvents. The perovskite film may serve as a photoactive layer
in optoelectronic devices, where it may absorb incident light and generate charge
carriers for device operation.
15 [0046] Embodiments herein provide a perovskite solar cell. The perovskite solar
cell, according to embodiments herein, comprises the perovskite film as disclosed
herein.
[0047] In some embodiments, there is provided a perovskite solar cell comprising
a substrate and the perovskite film deposited on the substrate. The perovskite film
20 may be deposited on the substrate to form a photovoltaic device structure.
[0048] The substrate may comprise glass, plastic, or steel that provides mechanical
support for the device layers. In an embodiment, the substrate is glass, preferably
indium tin oxide-coated glass. The substrate, preferably indium tin oxide-coated
glass, may be sequentially cleaned using soap solution, de-ionized water, acetone,
25 and isopropanol, and blow-dried with nitrogen and heated, preferably at 150
o
C for
10 minutes, prior to deposition of the perovskite film.
[0049] The perovskite film may be deposited directly onto the substrate or onto
one or more intermediate layers formed on the substrate surface. In some
embodiments, the substrate may be transparent to allow light transmission to the
30 perovskite film for photovoltaic operation. The perovskite film may be formed
through solution processing techniques such as spin-coating, blade-coating, slot-die
11
coating, spray-coating, or vapor deposition, followed by thermal annealing to
achieve the desired crystalline structure and morphology. In some embodiments,
the perovskite solar cell may further include additional functional layers such as
electron transport layers, hole transport layers, and electrodes to complete the solar
5 cell architecture and enable charge extraction and collection. The perovskite film
deposited on the substrate may serve as the primary light-absorbing component that
converts incident photons into electrical energy through the generation and
separation of charge carriers.
[0050] In an embodiment, the perovskite solar cell comprises: (a) a hole transport
10 layer or electron transport layer between the substrate and the perovskite film; a
hole transport layer or electron transport layer on top of the perovskite film; a
cathode layer electrically coupled to the electron transport layer; and an anode layer
electrically coupled to the hole transport layer.
[0051] In an embodiment, there is provided a perovskite solar cell, wherein the hole
15 transport layer comprises 2-(3,6-dimethoxy-9H-carbazol-9-yl) ethyl] phosphonic
acid (MeO-2PACz), PEDOT:PSS, NiOx, Me-4PACz, Me-2PACz, Spiro-
MeOTAD, or combination thereof.
[0052] In another embodiment, there is provided a perovskite solar cell, wherein
the electron transport layer comprises phenyl-C61-butyric acid methyl ester
20 (PCBM), bathocuproine (BCP), buckminsterfullerene (C60), tin oxide (SnO2),
titanium dioxide (TiO2), or combination thereof.
[0053] The electrodes (cathode/anode layer), according to embodiments herein,
may comprise conductive materials such as indium tin oxide or fluorine-doped tin
oxide, and/or metal such as gold, silver, or aluminum. In an embodiment, there is
25 provided a perovskite solar cell, wherein each of the cathode and the anode layer
comprises of silver, gold, carbon, aluminium, indium-tin oxide, indium-doped zinc
oxide, fluorine-doped tin oxide, aluminium-doped zinc oxide, or combination
thereof. The term “cathode” as used herein refers to a negatively charged electrode.
The term “anode” as used herein refers to a positively charged electrode.
30 Accordingly, the term “cathode layer” refers to a negatively charged material, and
12
the term “anode layer” refers to a positively charged material, which may be
deposited in a substrate such as glass.
[0054] The anode layer, according to embodiments herein, may be electrically
coupled with the HTL (hole transport layer), whereas the cathode may be
5 electrically coupled to an ETL (electron transport layer). In an embodiment, the
cathode layer is selected from indium tin oxide or fluorine-doped tin oxide layer. In
another embodiment, the cathode layer is selected from indium tin oxide or
fluorine-doped tin oxide, wherein the cathode layer is deposited on glass. The
electron transport layer may further be deposited on the cathode layer. In another
10 embodiment, the cathode layer is selected from indium tin oxide or fluorine-doped
tin oxide, wherein the cathode layer is deposited on glass followed by the electron
transport layer. In an embodiment, the anode layer is gold. In an embodiment, the
anode layer is gold, wherein the anode layer is deposited on HTL.
[0055] In another embodiment, the anode layer is selected from indium tin oxide
15 or fluorine-doped tin oxide, wherein the anode layer is deposited on glass. The hole
transport layer may further be deposited on the anode layer. In another embodiment,
the anode layer is selected from indium tin oxide or fluorine-doped tin oxide,
wherein the anode layer is deposited on glass followed by the hole transport layer.
In an embodiment, the anode layer is gold. In an embodiment, the anode layer is
20 gold, wherein the anode layer is deposited on HTL. In an embodiment, the cathode
layer is selected from silver or aluminium, wherein the cathode layer is deposited
on ETL.
[0056] The anode layer may be of a thickness ranging from about 80 nm to about
120 nm, and may provide electrical contact for hole collection. The anode may be
25 deposited as the top electrode in the solar cell stack. In other examples, the cathode
may comprise transparent conductive materials such as indium tin oxide (ITO) or
fluorine-doped tin oxide (FTO) deposited on a glass substrate to serve as the bottom
electrode, allowing light transmission to reach the perovskite film layer. The
cathode layer may have a thickness of about 80 nm to about 200 nm and may
30 provide the foundation for subsequent layer deposition.
13
[0057] In other examples, the anode may comprise transparent conductive materials
such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO) deposited on the
glass substrate to serve as the bottom electrode, allowing light transmission to reach
the perovskite active layer. The anode may have a thickness of about 100 nm to
5 about 200 nm and may provide the foundation for subsequent layer deposition.
[0058] The perovskite solar cell, according to some embodiments herein, may
comprise a substrate and a perovskite film configured to achieve enhanced
photovoltaic performance characteristics. The perovskite solar cell may exhibit a
short-circuit current density (Jsc) in the range of 18 to 26 mA/cm2, which may be
10 attributed to efficient light absorption and charge generation within the perovskite
active layer. In some aspects, the open-circuit voltage (Voc) may range from 0.9 to
1.2 V, reflecting favorable energy level alignment and reduced recombination
losses at the interfaces. The fill factor (FF) may range from 65 to 85%, indicating
good carrier collection efficiency and minimal series resistance within the device
15 structure. In some cases, the power conversion efficiency (PCE) may range from
15 to 27%, demonstrating the overall photovoltaic performance of the device under
standard test conditions.
Methods
20 [0059] Embodiments herein provide a method for preparing the perovskite film.
The method for preparing the perovskite film, according to embodiments herein,
method comprises: (a) dissolving the perovskite precursors in a first solvent to form
a solution; (b) heating the solution to precipitate the perovskite powder; (c) filtering
the perovskite powder; and (d) redissolving the perovskite powder in a second
25 solvent mixture to form the perovskite ink.
[0060] In an embodiment, there is provided a method comprising: (a) dissolving
the perovskite precursors in a first solvent to form a solution; (b) heating the
solution to precipitate the perovskite powder; (c) filtering the perovskite powder;
and (d) redissolving the perovskite powder in a second solvent mixture to form the
30 perovskite ink, wherein the perovskite ink has a viscosity in a range of 1 mPa·s and
10 mPa·s; and the perovskite ink has a bimodal size distribution comprising a first
14
population of particles having sizes in a range of about 1 nm to about 20 nm and a
second population of particles having sizes in a range of about 100 nm to about
30000 nm.
[0061] In an embodiment, the perovskite precursors are selected from the group
5 consisting of methylammonium iodide (MAI), acetamidinium iodide (AAI),
formamidinium iodide (FAI), caesium iodide (CsI), lead bromide (PbBr2),
methylammonium bromide (MABr), lead iodide (PbI2) or mixtures thereof.
[0062] In an embodiment, the perovskite powder comprises a perovskite selected
from (MAxAA1-x)PbI3, FAPbI3, Cs0.05(FAxMA1-x)Pb(I0.9Br0.3)3, or MAPbI3,
10 wherein MA is methylammonium, AA is acetamidinium, FA is formamidinium,
and x is a value between 0.5 and 1.
[0063] In an embodiment, the first solvent is a solvent having a negative solubility
coefficient, preferably selected from 2-methoxyethanol (2-MOE), γ-butyrolactone
(GBL), dimethylformamide (DMF), or combinations thereof, and the second
15 solvent is selected from acetonitrile, dimethyl formamide (DMF), dimethyl
sulfoxide (DMSO), γ-butyrolactone (GBL), N-methyl-2-pyrrolidone (NMP), or
combinations thereof. The terms solvent and second solvent, in the present
disclosure, are used interchangeably herein.
[0064] The perovskite precursor may be dissolved in a first solvent to form a
20 solution, according to embodiments of the method disclosed herein. In an example,
perovskite precursor: MAI, AAI, and PbI2 in a ratio of 9:1:10 may be dissolved in
2-methoxyethanol (2-MEO) to form a 2 M solution. In an embodiment, there is
provided a method for preparing the perovskite film, wherein the dissolving is
carried out by stirring the solution at a temperature in range 20℃ to 70℃ for a time
25 period of 4hours to overnight.
[0065] The precursor solution may be heated to precipitate the perovskite powder,
according to embodiments of the method disclosed herein. In an example, the
solution may be heated at 60℃ to 120℃, for a period of 70 to 120 minutes. In an
embodiment, there is provided a method wherein the heating is carried out at a
30 temperature in a range of 60℃ to 120℃ for a time period in a range of 70 to 120
minutes.
15
[0066] The perovskite powder may be filtered and redissolved in a second solvent
to form the perovskite ink. The second solvent, in an embodiment, a combination
of DMF and DMSO. In some examples, the precipitated perovskite powder may be
separated from the solution using filtration techniques to obtain a solid powder
5 material. The filtering step may remove excess solvent and unreacted precursors,
resulting in a purified perovskite powder suitable for redissolution. In some
examples, the filtered perovskite powder may be redissolved in a second solvent to
form the perovskite ink, also known as powder processing (PP) route herein. This
redissolution step may result in a perovskite ink having different particle size
10 distribution characteristics compared to standard processing (SP) methods, with the
PP route showing modified particle size distributions and reduced viscosity
compared to standard preparation (SP) methods. The second solvent, in an
embodiment, is a combination of DMF and DMSO.
[0067] In the SP method, the perovskite precursors may be directly dissolved in
15 DMF-DMSO solvent at room temperature with stirring to form the perovskite ink.
This SP route, have been observed by the present inventors, to result in a perovskite
ink having: a particle size distribution primarily showing larger particles in the
range of 1000-10000 nm, as evidenced by the dynamic light scattering
measurements; higher viscosity values around 4.5 mPa·s compared to the PP route;
20 smaller grain sizes in the resulting perovskite films, as shown in the SEM images;
etc.
[0068] In an embodiment, the second solvent is a combination of DMF and DMSO
in a volume ratio in a range of 2: 1 to 10:1, preferably 9:1. In an embodiment, the
perovskite powder is in a concentration range of 0.5 to 2 M, preferably 1.2M, in the
25 second solvent.
[0069] In an embodiment, there is provided a method, wherein the perovskite ink
is optionally sonicated or filtered.
[0070] Embodiments herein provide a method of fabricating a perovskite solar cell.
The method of fabricating the perovskite solar cell, according to embodiments
30 herein, may comprise sequential deposition of functional layers to form a complete
solar cell. The anode or cathode layer may be coated on a substrate such as glass
16
using techniques such as sputtering, thermal evaporation, or solution processing to
form a transparent conductive electrode. In some embodiments, the hole transport
layer or electron transport layer may be deposited on the substrate using spin-
coating, blade coating, thermal evaporation, sputtering, spray coating, and slot-die
5 coating to obtain a charge transport layer coated substrate with uniform coverage
and appropriate thickness. The perovskite ink may be deposited on the charge
transport layer coated substrate using spin-coating techniques, where the ink may
be applied at controlled spin speeds and durations to achieve the desired film
thickness and uniformity. In some cases, an antisolvent treatment may be applied
10 during the spin-coating process to promote rapid crystallization and improve film
quality. The perovskite film may be subjected to heat treatment at temperatures
ranging from about 60°C to about 150°C for durations of about 5 minutes to about
60 minutes to remove residual solvents, promote crystallization, and optimize film
properties. The electron transport layer and/or hole transport layer may then be
15 coated over the perovskite film, followed by deposition of the cathode or anode
layer to complete the solar cell architecture and enable charge collection from both
sides of the perovskite film layer.
[0071] Accordingly, in an embodiment, the method of fabricating the perovskite
solar cell comprises: (a) coating an anode/cathode layer on substrate; (b) coating a
20 hole transport layer or electron transport layer on the substrate to obtain a hole
transport layer or electron transport layer coated substrate; (c) depositing the
perovskite ink on the hole transport layer or electron transport layer coated substrate
to form a perovskite film; (d) subjecting the perovskite film to a heat treatment; and
(e) coating the hole transport layer or electron transport layer, followed by
25 cathode/anode layer over the perovskite film.
[0072] Embodiments of the method of fabricating the perovskite solar cell,
according to the present disclosure, includes coating an anode/cathode layer on
substrate. In some examples, coating may be by sputtering indium tin oxide (ITO)
onto a glass substrate to form a transparent anode layer with a thickness of about
30 100 nm to about 200 nm. In other examples, silver or aluminum may be thermally
evaporated on the top layer to form the electrode layers.
17
[0073] In an embodiment, there is provided a method of fabricating the perovskite
solar cell, wherein coating the anode/cathode layer on a substrate comprises coating
indium tin oxide (ITO) on a glass substrate.
[0074] In an embodiment, there is provided a method of fabricating the perovskite
5 solar cell, wherein coating the anode/cathode layer on a substrate comprises coating
silver on the hole transport layer or electron transport layer.
[0075] In an embodiment, there is provided a method of fabricating a perovskite
solar cell, wherein the coating of hole transport layer, electron transport layer,
perovskite, anode, and cathode is performed by spin-coating, blade coating, thermal
10 evaporation, sputtering, spray coating, and slot-die coating.
[0076] In an embodiment, coating of the hole transport layer or electron transport
layer on the substrate is carried out at a speed in a range of 2000 to 8000 rpm,
preferably 2000 to 5000 rpm, for a time period in a range of 30 to 60 seconds.
[0077] In some aspects, the hole transport layer may comprise materials such as 2-
15 (3,6-dimethoxy-9H-carbazol-9-yl) ethyl] phosphonic acid (MeO-2PACz),
poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), nickel
oxide (NiOx), Me-4PACz, Me-2PACz, spiro-MeOTAD, or combinations thereof,
which may be deposited using thermal evaporation technique, sputtering, pulsed
laser deposition, spin-coating, blade-coating, or solution processing techniques. In
20 some aspects, the electron transport layer may comprise materials such as phenyl-
C61-butyric acid methyl ester (PCBM), bathocuproine (BCP),
buckminsterfullerene (C60), tin oxide (SnO2), titanium dioxide (TiO2), or
combinations thereof, which may be deposited through sol-gel processing, thermal
evaporation, atomic layer deposition, or sputtering methods.
25 [0078] In an embodiment, there is provided a method of fabricating a perovskite
solar cell, wherein depositing the perovskite ink is carried out by spin-coating at a
speed in a range of 3000 to 6000 rpm for a time period of 20 to 60 seconds. The
perovskite ink may be deposited using spin-coating process, where the ink is
applied at 4000 rpm for 25 seconds. During the spinning step, an antisolvent such
30 as chlorobenzene or diethyl ether may be dripped, preferably at 8th second, onto the
spinning substrate to promote rapid crystallization.
18
[0079] Accordingly, in an embodiment, there is provided a method of fabricating a
perovskite solar cell, wherein depositing the perovskite ink comprises dripping an
antisolvent onto the substrate at a time period of 5 to 20 seconds after the initiation
of the deposition of the perovskite ink; and the antisolvent is selected from a group
5 consisting of chlorobenzene, isopropanol, acetonitrile, diethyl ether, or combination
thereof.
[0080] In some instances, the coated layer may be subjected to thermal treatment at
temperatures ranging from about 60°C to about 200°C to remove solvents, promote
crystallization, and optimize the electronic properties of the charge transport layer.
10 In an embodiment, there is provided a method of fabricating a perovskite solar cell,
wherein the perovskite film is subjected to the heat treatment at a temperature in a
range of 60°C to 150°C for a time period in a range of 1 to 30 minutes.
[0081] In an example, an electron transport layer (ETL) may be deposited on the
perovskite film, followed by a cathode layer to complete the solar cell architecture.
15 The electron transport layer may comprise materials such as PCBM or
C60 deposited by spin-coating or thermal evaporation to facilitate electron
extraction from the perovskite layer. In other examples, a hole transport layer (HTL)
may be applied over the perovskite film followed by deposition of an anode layer.
The final electrode layer may be deposited by thermal evaporation or sputtering to
20 provide electrical contact for charge collection.
[0082] In an embodiment, there is provided a method of fabricating a perovskite
solar cell, wherein coating of the hole transport layer or electron transport layer on
the perovskite ink deposited substrate is carried out at a speed in a range of 2000 to
8000 rpm, preferably 4000 to 6000 rpm, for a time period in a range of 30 to 60
25 seconds.
[0083] In an embodiment, there is provided a method of fabricating a perovskite
solar cell, wherein the perovskite film has an average grain size in a range of 100
nm to 600 nm, preferably 200 nm to 500 nm; thickness in a range of 200 nm to 600
nm, 300 nm to 400 nm; and density in a range of 6.0 g/cm3 to 7.0 g/cm3, preferably
30 6.40 g/cm3 to 7.10 g/cm3.
19
[0084] In some embodiments, a perovskite solar cell may comprise a perovskite
film disposed between hole/electron transport layers to form a photovoltaic device.
The perovskite solar cell may include a substrate, such as glass, upon which
functional layers are sequentially deposited. An electron transport layer may be
5 positioned adjacent to the perovskite film to facilitate electron extraction and
transport to a cathode electrode. In some embodiments, a hole transport layer may
be positioned on the opposite side of the perovskite film to facilitate hole extraction
and transport to an anode electrode. The perovskite film may serve as the
photoactive layer that absorbs incident light and generates electron-hole pairs
10 through the photovoltaic effect. In some cases, the perovskite solar cell may further
comprise additional functional layers such as buffer layers, interfacial layers, or
protective layers to enhance device performance and stability. The electrodes may
comprise transparent conductive materials such as indium tin oxide or fluorine-
doped tin oxide for light transmission, and metal contacts such as gold, silver, or
15 aluminum for charge collection.
[0085] In an embodiment, the method of fabricating the perovskite solar cell
comprises: (a) coating an anode/cathode layer on substrate; (b) coating a hole
transport layer on the substrate to obtain a hole transport layer coated substrate; (c)
depositing the perovskite ink on the hole transport layer coated substrate to form a
20 perovskite film; (d) subjecting the perovskite film to a heat treatment; and (e)
coating at least one electron transport layers, followed by cathode/anode layer over
the perovskite film.
[0086] Embodiments, according to the present disclosure, provides several
advantages over conventional technologies. The perovskite ink, according to the
25 present disclosure, exhibits a desired particle size, viscosity, which results in better
coating. In some aspects, the perovskite ink as disclosed herein results in a desired
particle size showing a higher percentage of small sized particles (bimodal size
distribution) grain which contribute to improved film formation characteristics and
enhanced grain growth during subsequent processing steps. The viscosity of the
30 perovskite ink, according to embodiments herein facilitates better coating
20
uniformity and processing characteristics during film deposition, potentially
leading to improved device fabrication reproducibility.
[0087] The perovskite film prepared using the disclosed perovskite ink
demonstrates enhanced morphological properties, including larger grain structures
5 as evidenced by scanning electron microscopy analysis. These larger grains may
reduce grain boundary density and associated defect states, potentially improving
charge transport properties and device performance.
[0088] The perovskite solar cells may exhibit improved performance
characteristics, including enhanced current generation and voltage characteristics.
10
Example 1: Preparation of perovskite ink via powder processing (PP) Route
[0089] Methylammonium iodide (MAI, 286.14 mg), acetamidinium iodide (AAI,
37.17 mg), and lead iodide (PbI2, 922 mg) (in a ratio of 9:1:10) were first dissolved
in 2-methoxyethanol (1 mL) (first solvent) at room temperature with stirring. The
15 solution was then heated at 70°C for 90 minutes to precipitate perovskite powder
((MA0.9AA0.1)PbI3). The precipitated powder was filtered and collected. The
filtered perovskite powder was dried at 70°C for 10 minutes. Subsequently, the
powder was redissolved in a DMF-DMSO (9:1) mixture (solvent) to form the
perovskite ink (1.2M). The ink may be sonicated or filtered to obtain selective
20 particle size ranges. The resulting ink exhibited a higher percentage of smaller
particles in ink, bimodal size distribution and a reduced viscosity. The resulting ink
exhibited a broader particle size distribution with peaks around 300-400 nm and a
reduced viscosity of approximately 4.0 mPa·s.
25 Example 2: Preparation of perovskite ink via Standard Processing (SP) Route
[0090] Methylammonium iodide (MAI, 171.68 mg), acetamidinium iodide (AAI,
22.30 mg), and lead iodide (PbI2, 553.21 mg) (in a ratio of 9:1:10) were dissolved
in a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO)
in a volume ratio of 9:1 (total volume 1 mL) at room temperature. The mixture was
30 stirred for at least 4 hours until a clear, homogeneous solution was obtained,
forming the perovskite ink directly. The resulting ink exhibited a thin film with
21
grain size distribution having peaks primarily in the range of 100-200 nm and a
viscosity of approximately 4.5 mPa·s.
Example 3: Fabrication of Perovskite Solar Cell
5 [0091] Perovskite solar cells were fabricated using the ink from Example 1 and
Example 2. Indium tin oxide-coated glass (ITO) coated glass was used as the
substrate. Indium tin oxide-coated glass substrate was sequentially cleaned in soap
solution, de-ionized water, acetone, and isopropanol, then blow-dried with nitrogen
and heated at 150°C for 10 minutes to prepare the substrate surface. MeO-2PACz
10 ([2-(3,6-Dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid) was used as the hole
transport layer. A 0.5 mg/ml solution in ethanol was spin-coated at 3000 rpm for 45
seconds, followed by annealing at 100°C for 7 minutes. The substrate was then
washed with ethanol and annealed for an additional 5 minutes.
[0092] Perovskite inks obtained from Example 1 and Example 2 (1.2M
15 concentration) were spin-coated at 4000 rpm for 25 seconds with chlorobenzene
antisolvent dripped at the 8th second from the beginning of the spin-coating process.
The coated perovskite film was sequentially annealed at 65°C for 1 minute and
100°C for 5 minutes to promote crystallization and remove residual solvents.
[0093] PCBM (phenyl-C61-butyric acid methyl ester) solution (20 mg/ml in
20 chlorobenzene) was spin-coated at 2000 rpm for 60 seconds as the electron
transport layer, followed by annealing at 100°C for 10 minutes. BCP
(bathocuproine) solution (0.5 mg/ml in isopropanol) was then spin-coated at 6000
rpm for 60 seconds.
[0094] Silver was thermally evaporated as the top electrode at a base pressure of
25 1×10-
6
mbar to obtain a 100 nm thick film.
Example 4: Characterization data for perovskite ink
The characterization was done for thin films synthesised the perovskite ink
(Examples 1 and Example 2). A comparative dataset for the perovskite ink
30 produced using the standard process route (salt-processed, SP) and powder-
processed (PP) thin films is given in Table 1.
22
Table 1:
Parameter SP PP
Particle size distribution >1000nm 1-6nm (first population) and 400-
10000 nm (second population)
Thin film grain size (nm) 148 ± 48 280 ± 10
Thin film thickness (nm) 420 ± 10 380 ± 10
Thin film density (g/cm3) 5.89 ± 0.29 6.76 ± 0.31
Precursor viscosity (mPa.s) 4.55 ± 0.19 4.00 ± 0.13
[0095] The thin film morphology for the films synthesised by the two process
routes (i.e. in Examples 1 and Example 2) was analysed. The grain size of PP thin
films was higher than SP films, with the average grain size being two times higher.
5 The cross-sectional SEM for PP films shows grains extending throughout the film
thickness, which was not the case for SP films. Figs. 1(a), 1(b) and 1(c) depict
characterization data for perovskite powder, wherein 1(a) depicts thin-film
morphology, 1(b) depicts thin film grain size distribution, and 1(c) depicts thin-film
cross-section for salt (SP) and powder processed (PP) routes.
10 [0096] Fig. 2 (a) depicts the XRD spectrum for PP and SP films, it shows no
significant change, stating that the PP route does not introduce any new phases or
segregations in the films. The absorption of the two films is also comparable (Fig.
2(b)), with the absorption coefficient being slightly higher for PP films.
[0097] The viscosity of the ink was measured by using a rheometer at room
15 temperature (about 20 to 25 °C). Particle size distribution of inks was evaluated by
using dynamic light scattering for low concentration (0.65M) of inks.
[0098] Fig. 3 depicts the viscosity for PP and SP processed perovskite ink. Figs.
4(a)-4(b) depicts particle size distribution for PP and SP processed perovskite ink.
20 Example 5: Characterization data for perovskite solar cell
[0099] Fig. 5 is a representation depicting the architecture followed for solar cell
fabrication using perovskite ink produced by PP and SP routes (refer Example 1
and Example 2). Fig. 6 depicts dark and light current density-voltage characteristics
for salt (SP) and powder (PP) processed film-based devices (Table 2).
25 Table 2:
23
Sr. no.
Stack Jsc (mA/cm2) Voc (V) FF (%) PCE (%)
1 Salt-processed 21.12 1.03 72.7 15.99
21.22 1.05 75.6 16.88
2 Powder-processed 24.30 1.08 79.9 20.99
24.29 1.08 80.3 21.17
[00100] Comparative photovoltaic performance data for perovskite solar cells
fabricated using salt-processed (SP route) and powder-processed (PP route)
methods were systematically evaluated and tabulated. The short-circuit current
density (Jsc) showed significant improvement from 21.22 mA/cm2 for salt-
5 processed devices to 24.29 mA/cm2 for powder-processed devices, representing an
enhancement of approximately 14.5%. This improvement may be attributed to the
increased grain size observed in powder-processed films, which reduces grain
boundary density and enhances charge carrier transport within the perovskite layer.
[00101] The open-circuit voltage (Voc) demonstrated a marginal improvement from
10 1.05 V for salt-processed devices to 1.08 V for powder-processed devices. The fill
factor (FF) showed notable enhancement from 75.6% to 80.3%, indicating
improved charge carrier collection efficiency and reduced series resistance in the
powder-processed devices. This improvement in fill factor may be related to the
optimized film morphology and reduced defect density achieved through the
15 powder processing approach.
[00102] Cumulatively, the power conversion efficiency (PCE) increased
substantially from 16.88% for salt-processed devices to 21.17% for powder-
processed devices, representing a relative improvement of approximately 25.4%.
These results demonstrate that tuning parameters such as viscosity, precursor
20 purity, and particle size through the powder processing route may result in
significantly enhanced performance of perovskite solar cells. The comprehensive
performance improvements across all key photovoltaic parameters confirm the
advantages of the present perovskite inks (Example 1) for achieving high-efficiency
perovskite solar cell devices.
25
24
I/We Claim:
1. A perovskite ink comprising:
(a) a perovskite powder; and
5 (b) a solvent in which the perovskite powder is dissolved,
wherein the perovskite ink has a viscosity in a range of 1 mPa·s and 10
mPa·s, and wherein the perovskite ink has a bimodal size distribution
comprising a first population of particles having sizes in a range of about 1
nm to about 20 nm and a second population of particles having sizes in a
10 range of about 100 nm to about 30000 nm.
2. The perovskite ink as claimed in claim 1, wherein the perovskite powder
comprises a perovskite compound selected from (MAxAA1-x)PbI3, FAPbI3,
Cs0.05(FAxMA1-x)Pb(I0.9Br0.3)3, or MAPbI3, wherein MA is
methylammonium, AA is acetamidinium, FA is formamidinium, and x is a
15 value between 0.5 and 1.
3. The perovskite ink as claimed in claim 1, wherein the solvent is selected
from dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), γ-
butyrolactone, acetonitrile, or combinations thereof.
4. The perovskite ink as claimed in claim 3, wherein the solvent is a
20 combination of DMF and DMSO in a volume ratio in a range of 2: 1 to 10:1.
5. A method for preparing the perovskite ink as claimed in claim 1, the method
comprising:
(a) dissolving perovskite precursors in a first solvent to form a solution;
(b) heating the solution to precipitate the perovskite powder;
25 (c) filtering the perovskite powder; and
(d) redissolving the perovskite powder in a second solvent to form the
perovskite ink.
6. The method as claimed in claim 5, wherein the perovskite precursors are
selected from the group consisting of methylammonium iodide (MAI),
30 acetamidinium iodide (AAI), formamidinium iodide (FAI), caesium iodide
25
(CsI), lead bromide (PbBr2), methylammonium bromide (MABr), lead
iodide (PbI2), or mixtures thereof.
7. The method as claimed in claim 5, wherein the perovskite powder comprises
the perovskite compound selected from (MAxAA1-x)PbI3, FAPbI3,
5 Cs0.05(FAxMA1-x)Pb(I0.9Br0.3)3, or MAPbI3, wherein MA is
methylammonium, AA is acetamidinium, FA is formamidinium, and x is a
value between 0.5 and 1.
8. The method as claimed in claim 5, wherein the first solvent is a solvent
having a negative solubility coefficient, preferably selected from 2-
10 methoxyethanol (2-MOE), γ-butyrolactone (GBL), dimethylformamide
(DMF), and the second solvent is selected from acetonitrile, dimethyl
formamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL),
N-methyl-2-pyrrolidone (NMP), or combinations thereof.
9. The method as claimed in claim 5, wherein the dissolving is carried out by
15 stirring the solution at a temperature in range 20℃ to 70℃ for a time period
of 4 hours to 12 hours.
10. The method as claimed in claim 5, wherein the heating is carried out at a
temperature in a range of 60℃ to 120℃ for a time period in a range of 70
to 120 minutes.
20 11. The method as claimed in claim 5, wherein the second solvent is a
combination of DMF and DMSO in a volume ratio in a range of 2: 1 to 10:1.
12. The method as claimed in claim 5, wherein the perovskite powder
concentration in the perovskite ink is in a range of 0.5 to 2 M.
13. The method as claimed in claim 5, wherein the perovskite ink is optionally
25 sonicated or filtered.
14. A perovskite film prepared using the perovskite ink of any of claims 1 to 4.
15. The perovskite film as claimed in claim 14, wherein the perovskite film has
an average grain size in a range of 100 nm to 600 nm; thickness in a range
of 200 nm to 600 nm.
30 16. A perovskite solar cell, comprising:
(a) a substrate; and
26
(b) the perovskite film as claimed in claim 14, deposited on the substrate.
17. The solar cell as claimed in claim 16, wherein the substrate is selected from
glass, steel, or plastic.
18. The solar cell as claimed in claim 16, wherein the solar cell further
5 comprises:
(a) a hole/electron transport layer between the substrate and the perovskite
film;
(b) an electron/hole transport layer on top of the perovskite film;
(c) a cathode layer electrically coupled to the electron transport layer; and
10 (d) an anode layer electrically coupled to the hole transport layer.
19. The solar cell as claimed in claim 16, wherein the hole transport layer
comprises 2-(3,6-dimethoxy-9H-carbazol-9-yl) ethyl] phosphonic acid
(MeO-2PACz), PEDOT:PSS, NiOx, Me-4PACz, Me-2PACz, Spiro-
MeOTAD, or combinations thereof.
15 20. The solar cell as claimed in claim 16, wherein the electron transport layer
comprises phenyl-C61-butyric acid methyl ester (PCBM), C60, SnO2, TiO2,
or combinations thereof.
21. The solar cell as claimed in claim 16, wherein the cathode and anode layer
comprises silver, gold, carbon, aluminium, indium-tin oxide, indium-doped
20 zinc oxide, fluorine-doped tin oxide, aluminium-doped zinc oxide, or
combinations thereof.
22. A method of fabricating the perovskite solar cell as claimed in claim 16, the
method comprising:
(a) coating an anode/cathode layer on a substrate;
25 (b) coating a hole/electron transport layer on the substrate to obtain a
hole/electron transport layer coated substrate;
(c) depositing the perovskite ink as claimed in claim 1 on the hole/electron
transport layer coated substrate to form a perovskite film;
(d) subjecting the perovskite film to heat treatment; and
30 (e) coating electron/hole transport layer followed by cathode/anode layer,
over the perovskite film.
27
23. The method as claimed in claim 22, wherein the coatings of hole transport
layer, electron transport layer, perovskite, anode, and cathode can be done
by spin-coating, blade coating, thermal evaporation, sputtering, spray
coating, or slot-die coating.
5 24. The method as claimed in claim 22, wherein coating the hole transport layer
on the substrate is carried out at a speed in a range of 2000 to 5000 rpm for
a time period in a range of 30 to 60 seconds.
25. The method as claimed in claim 22, wherein depositing the perovskite ink
on the substrate is carried out by spin-coating at a speed in a range of 3000
10 to 6000 rpm for a time period of 25 to 60 seconds.
26. The method as claimed in claim 22, wherein depositing the perovskite ink
comprises dripping an antisolvent onto the substrate at a time period of 5 to
20 seconds after the initiation of the deposition of the perovskite ink; and
the antisolvent is selected from chlorobenzene, isopropanol, acetonitrile,
15 diethyl ether, or combinations thereof.
27. The method as claimed in claim 22, wherein the perovskite film is subjected
to the heat treatment at a temperature in a range of 60°C to 150°C for a time
period in a range of 1 to 30 minutes.
28. The method as claimed in claim 22, wherein the perovskite film has an
20 average grain size in a range of 100 nm to 500 nm; and thickness in a range
of 200 nm to 600 nm.
29. The method as claimed in claim 22, wherein the perovskite solar cell
exhibits short-circuit current (Jsc) in a range of 18 to 26 mA/cm2; open-
circuit voltage (Voc) in a range of 0.9 to 1.2 V; fill factor (FF) in a range of
25 65 to 85%; and power conversion efficiency (PCE) in a range of 15 to 27%.
28
Date 24 September 2025
MALATHI LAKSHMIKUMARAN
IN/PA-1433
Agent for the Applicant
To,
The Controller of Patents
The Patent Office at Chennai
ABSTRACT
PEROVSKITE INK, SOLAR CELL, AND METHODS THEREOF
A perovskite ink for perovskite solar cells is disclosed herein. The perovskite
ink, as disclosed herein, comprises perovskite powder redissolved in a solvent
5 mixture. The perovskite ink has modified particle size distributions, larger grain
size, and reduced viscosity as compared to standard inks. Perovskite films
exhibit enhanced grain structures and morphology. Solar cells fabricated using
the perovskite ink as disclosed herein demonstrate improved photovoltaic
performance including enhanced power conversion efficiency, short-circuit
10 current density, and fill factor.
15
20
29
, Claims:I/We Claim:
1. A perovskite ink comprising:
(a) a perovskite powder; and
5 (b) a solvent in which the perovskite powder is dissolved,
wherein the perovskite ink has a viscosity in a range of 1 mPa·s and 10
mPa·s, and wherein the perovskite ink has a bimodal size distribution
comprising a first population of particles having sizes in a range of about 1
nm to about 20 nm and a second population of particles having sizes in a
10 range of about 100 nm to about 30000 nm.
2. The perovskite ink as claimed in claim 1, wherein the perovskite powder
comprises a perovskite compound selected from (MAxAA1-x)PbI3, FAPbI3,
Cs0.05(FAxMA1-x)Pb(I0.9Br0.3)3, or MAPbI3, wherein MA is
methylammonium, AA is acetamidinium, FA is formamidinium, and x is a
15 value between 0.5 and 1.
3. The perovskite ink as claimed in claim 1, wherein the solvent is selected
from dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), γ-
butyrolactone, acetonitrile, or combinations thereof.
4. The perovskite ink as claimed in claim 3, wherein the solvent is a
20 combination of DMF and DMSO in a volume ratio in a range of 2: 1 to 10:1.
5. A method for preparing the perovskite ink as claimed in claim 1, the method
comprising:
(a) dissolving perovskite precursors in a first solvent to form a solution;
(b) heating the solution to precipitate the perovskite powder;
25 (c) filtering the perovskite powder; and
(d) redissolving the perovskite powder in a second solvent to form the
perovskite ink.
6. The method as claimed in claim 5, wherein the perovskite precursors are
selected from the group consisting of methylammonium iodide (MAI),
30 acetamidinium iodide (AAI), formamidinium iodide (FAI), caesium iodide
(CsI), lead bromide (PbBr2), methylammonium bromide (MABr), lead
iodide (PbI2), or mixtures thereof.
7. The method as claimed in claim 5, wherein the perovskite powder comprises
the perovskite compound selected from (MAxAA1-x)PbI3, FAPbI3,
5 Cs0.05(FAxMA1-x)Pb(I0.9Br0.3)3, or MAPbI3, wherein MA is
methylammonium, AA is acetamidinium, FA is formamidinium, and x is a
value between 0.5 and 1.
8. The method as claimed in claim 5, wherein the first solvent is a solvent
having a negative solubility coefficient, preferably selected from 2-
10 methoxyethanol (2-MOE), γ-butyrolactone (GBL), dimethylformamide
(DMF), and the second solvent is selected from acetonitrile, dimethyl
formamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL),
N-methyl-2-pyrrolidone (NMP), or combinations thereof.
9. The method as claimed in claim 5, wherein the dissolving is carried out by
15 stirring the solution at a temperature in range 20℃ to 70℃ for a time period
of 4 hours to 12 hours.
10. The method as claimed in claim 5, wherein the heating is carried out at a
temperature in a range of 60℃ to 120℃ for a time period in a range of 70
to 120 minutes.
20 11. The method as claimed in claim 5, wherein the second solvent is a
combination of DMF and DMSO in a volume ratio in a range of 2: 1 to 10:1.
12. The method as claimed in claim 5, wherein the perovskite powder
concentration in the perovskite ink is in a range of 0.5 to 2 M.
13. The method as claimed in claim 5, wherein the perovskite ink is optionally
25 sonicated or filtered.
14. A perovskite film prepared using the perovskite ink of any of claims 1 to 4.
15. The perovskite film as claimed in claim 14, wherein the perovskite film has
an average grain size in a range of 100 nm to 600 nm; thickness in a range
of 200 nm to 600 nm.
30 16. A perovskite solar cell, comprising:
(a) a substrate; and
(b) the perovskite film as claimed in claim 14, deposited on the substrate.
17. The solar cell as claimed in claim 16, wherein the substrate is selected from
glass, steel, or plastic.
18. The solar cell as claimed in claim 16, wherein the solar cell further
5 comprises:
(a) a hole/electron transport layer between the substrate and the perovskite
film;
(b) an electron/hole transport layer on top of the perovskite film;
(c) a cathode layer electrically coupled to the electron transport layer; and
10 (d) an anode layer electrically coupled to the hole transport layer.
19. The solar cell as claimed in claim 16, wherein the hole transport layer
comprises 2-(3,6-dimethoxy-9H-carbazol-9-yl) ethyl] phosphonic acid
(MeO-2PACz), PEDOT:PSS, NiOx, Me-4PACz, Me-2PACz, Spiro-
MeOTAD, or combinations thereof.
15 20. The solar cell as claimed in claim 16, wherein the electron transport layer
comprises phenyl-C61-butyric acid methyl ester (PCBM), C60, SnO2, TiO2,
or combinations thereof.
21. The solar cell as claimed in claim 16, wherein the cathode and anode layer
comprises silver, gold, carbon, aluminium, indium-tin oxide, indium-doped
20 zinc oxide, fluorine-doped tin oxide, aluminium-doped zinc oxide, or
combinations thereof.
22. A method of fabricating the perovskite solar cell as claimed in claim 16, the
method comprising:
(a) coating an anode/cathode layer on a substrate;
25 (b) coating a hole/electron transport layer on the substrate to obtain a
hole/electron transport layer coated substrate;
(c) depositing the perovskite ink as claimed in claim 1 on the hole/electron
transport layer coated substrate to form a perovskite film;
(d) subjecting the perovskite film to heat treatment; and
30 (e) coating electron/hole transport layer followed by cathode/anode layer,
over the perovskite film.
23. The method as claimed in claim 22, wherein the coatings of hole transport
layer, electron transport layer, perovskite, anode, and cathode can be done
by spin-coating, blade coating, thermal evaporation, sputtering, spray
coating, or slot-die coating.
5 24. The method as claimed in claim 22, wherein coating the hole transport layer
on the substrate is carried out at a speed in a range of 2000 to 5000 rpm for
a time period in a range of 30 to 60 seconds.
25. The method as claimed in claim 22, wherein depositing the perovskite ink
on the substrate is carried out by spin-coating at a speed in a range of 3000
10 to 6000 rpm for a time period of 25 to 60 seconds.
26. The method as claimed in claim 22, wherein depositing the perovskite ink
comprises dripping an antisolvent onto the substrate at a time period of 5 to
20 seconds after the initiation of the deposition of the perovskite ink; and
the antisolvent is selected from chlorobenzene, isopropanol, acetonitrile,
15 diethyl ether, or combinations thereof.
27. The method as claimed in claim 22, wherein the perovskite film is subjected
to the heat treatment at a temperature in a range of 60°C to 150°C for a time
period in a range of 1 to 30 minutes.
28. The method as claimed in claim 22, wherein the perovskite film has an
20 average grain size in a range of 100 nm to 500 nm; and thickness in a range
of 200 nm to 600 nm.
29. The method as claimed in claim 22, wherein the perovskite solar cell
exhibits short-circuit current (Jsc) in a range of 18 to 26 mA/cm2; open-
circuit voltage (Voc) in a range of 0.9 to 1.2 V; fill factor (FF) in a range of
25 65 to 85%; and power conversion efficiency (PCE) in a range of 15 to 27%.