VISVESVARAYA TECHNOLOGICAL UNIVERSITY
JNANASANGAMA, BELAGAVI – 590018
TECHNICAL SEMINAR
(18ECS84)
“PEROVSKITE SOLAR CELLS”
Submitted in partial fulfillment of the requirements for the award of the degree
BACHELOR OF ENGINEERING
IN
ELECTRONICS AND COMMUNICATION ENGINEERING
For the Academic year 2022-2023
Report Submitted by:
SHUBHRA DIXIT (1MV19EC107)
Under the guidance of
Mrs. N. Bhuvaneswari
Assistant Professor
Dept of ECE
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
SIR M. VISVESVARAYA INSTITUTE OF TECHNOLOGY
Krishnadevaraya Nagar, Hunasamaranahalli, Bangalore-562157
2022-2023
SIR M. VISVESVARAYA INSTITUTE OF TECHNOLOGY
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING
CERTIFICATE
Certified that the Technical Seminar (18ECS86) on “PEROVSKITE SOLAR CELLS”
prepared by SHUBHRA DIXIT (1MV19EC107), a bonafide student of SIR M.
VISVESVARAYA INSTITUTE OF TECHNOLOGY. The report is in partial fulfillment of the
requirements for the award of the degree of “Bachelor of Engineering” in Electronics and
Communication Engineering. From the Visvesvaraya Technological University, Belagavi,
Karnataka, India, during the academic year 2022-2023. It is certified that all corrections/suggestions
indicated for Internal Assessment have been incorporated in the report submitted to the Department.
The Seminar report has been approved as it satisfies the academic requirement in respect to the work
prescribed for the said Degree.
-------------------------------
------------------------------
------------------------------
Signature of the Guide
Signature of HOD
Signature of Principal
Mrs. N. Bhuvaneswari
Dr. V. G. Supriya
Prof. Rakesh S.G.
Assistant Professor
Professor & Head
Dept of ECE
Dept of ECE
Principal
Sir MVIT, Bengaluru
ii
DECLARATION
I hereby declare the Seminar Report on “PEROVSKITE SOLAR CELLS” undertaken has
been presented under the guidance of Mrs. N. Bhuvaneswari, Assistant Professor, Department
of Electronics and Communication Engineering, Sir MVIT, Bengaluru. This topic has not
been submitted previously in the Dept. of ECE and any other Departments of Sir MVIT.
Place: Bengaluru
Shubhra Dixit
Date: 02/05/2023
1MV19EC107
iii
ACKNOWLEDGEMENT
A technical seminar is incomplete if it fails to thank all those instrumental in thesuccessful
completion of the report.
I welcome this opportunity to convey my regards, gratitude, respect, decorations, and a lot of
thanks to them who inspired me to complete this report in the stipulated period of time
provided.
It’s a great privilege to place on record my deep sense of gratitude to the Management and
Prof. Rakesh S.G., Principal, Sir M. Visvesvaraya Institute of Technology, who patronized
throughout our career & for the facilities provided to carry out this work successfully.
I would like to extend my heartfelt gratitude to Dr. V. G. Supriya, Professor and Head, Dept.
of ECE, SIRMVIT, for her constant support and encouragement.
I would like to thank our project guide Mrs. N. Bhuvaneswari, Assistant Professor, Dept. of
ECE, SIR MVIT, for her valuable guidance and support in the completion of this seminar.
I thank the teaching and non-teaching staff members who have helped me directly or
indirectly during the Internship.
Finally, I would also like to thank my parents and friends who rendered me active support for
the completion of this seminar report. I acknowledge them with a lot of gratitude and regard
and without all of the above this report may not be easily possible.
Shubhra Dixit
(1MV19EC107)
iv
ABSTRACT
Perovskite solar cells (PSCs) have emerged as a game-changing photovoltaic technology
due to their high-performance efficiency, low fabrication costs, and high tunability. Key
electronic and optical properties, such as high electron mobility, long diffusion wavelength,
and high absorption coefficient, have contributed to significant performance gains.
However, PSCs suffer from stability issues due to their vulnerability to moisture and
scalability challenges in manufacturing.
Regarding commercial applications, PSCs exhibit great potential as low-cost, efficient
photovoltaic technology, particularly in low-cost modules and tandem configurations.
Despite these advantages, the limited stability and element toxicity of PSCs must be
addressed before large-scale commercialization can be achieved. Tremendous research
efforts in compositional, process, and inter facial engineering have led to significant
achievements in device efficiency and stability.
To address the challenges facing PSCs, future innovations in the development of
environmentally friendly lead-free PSCs and high-efficiency multi-junction cells could
further improve their prospects for commercialization. Additionally, there is a need to
transition to manufacturing techniques that are compatible with roll-to-roll processing to
achieve high throughput. In conclusion, PSCs offer a promising solution to the quest for
low-cost and efficient photovoltaic technology, and overcoming the challenges associated
with their commercialization could revolutionize the field of solar energy.
v
TABLE OF CONTENTS
TOPIC
PAGE NO.
CERTIFICATE
ii
DECLARATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
TABLE OF CONTENTS
vi
LIST OF FIGURES
vii
CHAPTER 1: INTRODUCTION
08
CHAPTER 2: LITERATURE SURVEY
09
CHAPTER 3: IMPLEMENTATION
12
CHAPTER 4: PEROVSKITE FILMS PREPARATION
24
CHAPTER 5: APPLICATIONS
27
CHAPTER 6: ADVANTAGES AND DISADVANTAGES
28
CHAPTER 7: FUTURE ENHANCEMENT
30
CHAPTER 8: CONCLUSION
31
REFERENCES
32
vi
LIST OF FIGURES
Fig No
Figure Name
Page No.
Fig 1.1
Crystal structure of perovskite
8
Fig 3.1
Working principle of solar cell
12
Fig 3.2
Intrinsic silicon
16
Fig 3.3
Formation of potential barrier
18
Fig 3.4
Progress of cell efficiency
20
Fig 3.5
Demonstration of device structure of PSC
21
Fig 3.6
Fig 4.1
(a) The efficiency improvement tree of perovskite
solar cell using different hole transporting layers.
(b) Device architecture and molecular structure of
commonly used hole transporting materials.
(A) The Dual-source thermal evaporation
(B) One-step and two-step solution process for
perovskite film growth.
(C)Perovskite film formation through vapor
assisted deposition.
vii
23
24
CHAPTER – 1
INTRODUCTION
Solar energy is considered the most abundant and safe energy source as it provides the Earth's
surface with four million exajoules of solar radiation annually, which is more than what is used
in one year. The popularity of solar photovoltaics (PV) has grown exponentially in the past
decade. Solar PV capacity has reached a total of 709 GW, representing 24.3% of overall global
capacity. Solar PV is practical, low maintenance, and has a long lifetime, making it the
preferred choice for renewable energy.
The United Nations sustainable development goal aims to double the global rate of
improvement in energy efficiency by 2030, with a focus on renewable energy sources.
Photovoltaic (PV) technology is the most efficient renewable energy capacity to meet future
energy demands, but silicon PV technology alone cannot meet future energy demands.
Researchers are exploring alternative and efficient PV technology, which has led to an interest
in Perovskite Solar Cells (PSCs).
The first generation of solar cells is wafer-based with thickness ranging from a few hundred
micrometers.
Silicon-based
cells
dominate
the
market,
with
monocrystalline
and
polycrystalline solar cells being the two main types. Monocrystalline solar cells have achieved
a PCE of 26.6%, while polycrystalline solar cells are composed of various silicon crystals.
Perovskite Solar Cells (PSCs) are considered a third-generation solar cell and have drawn the
attention of researchers worldwide due to their potential to be more efficient than silicon-based
solar cells.
Fig 1.1 Crystal structure of perovskite
8
CHAPTER – 2
LITERATURE SURVEY
2.1 PAPER 1 -XiangRoy, P.; Ghosh, A.; Barclay, F.; Khare, A.; Cuce,
E. “Perovskite Solar Cells: A Review of the Recent Advances.”
Coatings 2022, 12, 1089. 31st July 2022.
This Perovskite solar cells (PSC) have been identified as a game-changer in the
world of photovoltaics. This is owing to their rapid development in performance
efficiency, increasing from 3.5% to 25.8% in a decade. Further advantages of PSCs
include low fabrication costs and high tunability compared to conventional siliconbased solar cells. This paper reviews existing literature to discuss the structural and
fundamental features of PSCs that have resulted in significant performance gains.
Key electronic and optical properties include high electron mobility (800 cm2/Vs),
long diffusion wavelength (1 μm), and high absorption coefficient (105 cm−1).
Synthesis methods of PSCs are considered, with solution-based manufacturing
being the most cost-effective and common industrial method. Furthermore, this
review identifies the issues impeding PSCs from large-scale commercialization and
the actions needed to resolve them. The main issue is stability as PSCs are
particularly vulnerable to moisture, caused by the inherently weak bonds in the
perovskite structure. Scalability of manufacturing is also a big issue as the spincoating technique used for most laboratory-scale tests is not appropriate for largescale production. This highlights the need for a transition to manufacturing
techniques that are compatible with roll-to-roll processing to achieve high
throughput. Finally, this review discusses future innovations, with the development
of more environmentally friendly lead-free PSCs and high-efficiency multi-junction
cells. Overall, this review provides a critical evaluation of the advances,
opportunities and challenges of PSCs.
9
2.2 PAPER 2 – Chenya Zhang P, Li M and Chen W-C. “A Perspective on
Perovskite Solar Cells: Emergence, Progress, and Commercialization.”
Front. Chem. 10:802890. 11th April 2022.
In this review, with rapid progress in light-to-electric conversion efficiencies, perovskite solar
cells (PSCs) have exhibited great potential as next-generation low-cost, efficient photovoltaic
technology. In this perspective, we briefly review the development of PSCs from discovery to
laboratory research to commercializing progress. The past several decades have witnessed
great achievement in device efficiency and stability due to tremendous research efforts on
compositional, process, and inter facial engineering. Regarding commercial applications, we
expound the merits and disadvantages of PSCs compared to the existing silicon photovoltaic
technologies. Although PSCs promise solution processability and low manufacturing cost, their
limited stability and element toxicity should to be addressed on the path to commercialization.
Finally, we provide future perspectives on commercialization of PSCs in the photovoltaic
marketplace. It is suggested that PSCs will be more promising in low-cost modules and tandem
configurations.
10
2.3 PAPER-3 Sandeep Pandey, Manoj Karakoti, Dinesh Bhardwaj, Gaurav
Tatrari, Richa Sharma, Lata Pandey, Man-Jong Lee and Nanda Gopal
Sahoo. “Recent advances in carbon-based materials for high-performance
perovskite solar cells: gaps, challenges and fulfilment.” Nanoscale Adv.,
2023, 5, 1492. 6th February 2023.
In Carbon-based materials have showed significant development in the last few decades.
Because of their high conductivity, vast surface area and excellent optoelectronic properties,
many carbon-based materials have shown potential as electrode materials in PSCs. The
present review summarized the most prominent and advance works regarding the
development of carbon-based PSCs. The procedures for the fabrication of carbon-based
electrodes and scale-up methods such as screen-printing, slot-die coating, ink-jet printing and
electro-deposition methods for carbon-based PSCs were clearly depicted. Graphite, carbon
black, carbon nanoparticles, graphene and carbon nanotubes have been demonstrated as
potential candidates for the fabrication of the back electrodes in PSCs, while graphene and
CNTs also showed potential as material for the front TCEs in PSCs. Interface engineering
between carbon and the perovskite phase can enhance the device parameters, while the
incorporation of conducting nanoparticles in the carbon matrix can reduce the sheet resistance
of carbon electrodes. Further, to develop cost-effective carbon-based back electrode systems
in PSCs, cost-effective carbon materials are also required, which depends on the process for
their synthesis. In this case, the use of solid waste-derived carbon materials can become a
cost-effective method for the large-scale production of carbon materials as the back and front
electrodes in PSCs.
11
CHAPTER -3
IMPLEMENTATION
3.1 WHAT IS SOLAR CELL?
A solar cell (photovoltaic cell or photoelectric cell) is a solid-state electrical device that
converts the energy of light directly into electricity by the photovoltaic effect. The energy of
light is transmitted by photons-small packets or quanta of light. Electrical energy is stored in
electromagnetic fields, which in turn can make a current of electrons flow.
Assemblies of solar cells are used to make solar modules which are used to capture energy
from sunlight. When multiple modules are assembled together (such as prior to installation on a
pole-mounted tracker system), the resulting integrated group of modules all oriented in one
plane is referred as a solar panel. The electrical energy generated from solar modules, is an
example of solar energy. Photovoltaics’ is the field of technology and research related to the
practical application of photovoltaic cells in producing electricity from light, though it is often
used specifically to refer to the generation of electricity from sunlight. Cells are described as
photovoltaic cells when the light source is not necessarily sunlight. These are used for detecting
light or other electromagnetic radiation near the visible range, for example infrared detectors,
or measurement of light intensity.
Fig 3.1 Working principle of a solar cell
12
3.2 HISTORY AND DEVELOPMENT OF SOLAR CELL TECHNOLOGY
The development of solar cell technology began with the 1839 research of French physicist
Antoine-César Becquerel. Becquerel observed the photovoltaic effect while experimenting
with a solid electrode in an electrolyte solution when he saw a voltage develop when light fell
upon the electrode. The major events are discussed briefly below, and other milestones can be
accessed by clicking on the image shown below.

Charles Fritts - First Solar Cell: The first genuine solar cell was built around 1883 by
Charles Fritts, who used junctions formed by coating selenium (a semiconductor) with an
extremely thin layer of gold. The device was only about 1 percent efficient.

Albert Einstein - Photoelectric Effect: Albert Einstein explained the photoelectric effect
in 1905 for which he received the Nobel Prize in Physics in 1921.

Russell Ohl - Silicon Solar Cell: Early solar cells, however, had energy conversion
efficiencies of less than one percent. In 1941, the silicon solar cell was invented by Russell
Ohl.

Gerald Pearson, Calvin Fuller and Daryl Chapin - Efficient Solar Cells: In 1954, three
American researchers, Gerald Pearson, Calvin Fuller and Daryl Chapin, designed a silicon
solar cell capable of six percent energy conversion efficiency with direct sunlight. They
created the first solar panels. Bell Laboratories in New York announced the prototype
manufacture of a new solar battery. Bell had funded the research. The first public service
trial of the Bell Solar Battery began with a telephone carrier system (Americus, Georgia)
on October 4 1955.
13
3.3 GENERATIONS OF SOLAR CELLS
First Generation: Crystalline Silicon Solar Cell Technology
First generation solar cells are the larger, silicon-based photovoltaic cells. Silicon's ability to
remain a semiconductor at higher temperatures has made it a highly attractive raw material for
solar panels. Silicon's abundance, however, does not ease the challenges of harvesting and
processing it into a usable material for microchips and silicon panels. Solar cells, use silicon
wafers consisting of Silicon or Germanium that are doped with Phosphorus and Boron in a pnjunction. Silicon cells have a quite high efficiency, but very pure silicon is needed, and due to
the energy-requiring process, the price is high compared to the power output. Crystalline
Silicon Solar Cells dominate 80-90% of solar cell market due to their high efficiency, despite
their high manufacturing costs
Second Generation: Thin Film Solar Cell Technology
Second generation solar cell, also known as thin-film solar cell (TFSC) or thin-film
photovoltaic cell (TFPV), is made by depositing one or more thin layers (thin films) of
photovoltaic material on a substrate. They are significantly cheaper to produce than first
generation cells but have lower efficiencies. The great advantage of thin-film solar cells, along
with low cost, is their flexibility and versatility to be used in varied environments. This has led
to aesthetically pleasing solar innovations such as solar shingles, solar glass and solar panels
that can be rolled out onto a roof or other surface. The most successful second-generation
materials have been cadmium telluride (CdTe), copper indium gallium selenide (CIGS),
amorphous silicon and micro amorphous silicon. The thickness range of such a layer is wide
and varies from a few nanometers to tens of micrometers. These materials are applied in a thin
film to a supporting substrate such as glass or ceramics reducing material mass and therefore
costs. It is predicted that second generation cells will dominate the residential solar market.
Third Generation: Dye-Sensitized Solar Cell Technology
The electrochemical dye solar cell was invented in 1988 by Professor Graetzel of Lausanne
Polytechnique, in Switzerland. The "Graetzel" dye cell uses dye molecules adsorbed in
nanocrystalline oxide semiconductors, such as TiO2, to collect sunlight. Dye cells employ
relatively inexpensive materials such as glass, Titania powder, and carbon powder. Graetzel's
14
cell is composed of a porous layer of titanium dioxide nanoparticles, covered with a molecular
dye that absorbs sunlight, like the chlorophyll does in green leaves. Third generation solar cells
are the cutting edge of solar technology. These solar cells can exceed the theoretical solar
conversion efficiency limit for a single energy threshold material. Current research is targeting
conversion efficiencies of 30-60% while retaining low-cost materials and manufacturing
techniques. Third generation contains a wide range of potential solar innovations including
multifunction solar cells, polymer solar cells, nanocrystalline-nanowire cells, quantum dot solar
cells and dye sensitized solar cells.
15
3.4 HOW DO SOLAR CELLS WORK?
Solar cells, which largely are made from crystalline silicon work on the principle of
Photoelectric Effect that this semiconductor exhibits. Silicon in its purest form, Intrinsic
Silicon is doped with a dopant impurity to yield Extrinsic Silicon of desired characteristic (ptype or n-type Silicon). Working of Solar cells can thus be based on crystalline structure of
Intrinsic and Extrinsic Silicon. When p and n type silicon combine, they result in formation of
potential barrier. These and more are discussed below.
Pure Silicon (Intrinsic) Crystalline Structure
Silicon has some special chemical properties, especially in its crystalline form. An atom of
silicon has 14 electrons, arranged in three different shells. The first two shells- which hold two
and eight electrons respectively- are completely full. The outer shell, however, is only half full
with just four electrons (Valence electrons). A silicon atom will always look for ways to fill up
its last shell, and to do this, it will share electrons with four nearby atoms. It's like each atom
holds hands with its neighbors, except that in this case, each atom has four hands joined to four
neighbors. That's what forms the crystalline structure. The only problem is that pure crystalline
silicon is a poor conductor of electricity because none of its electrons are free to move about,
unlike the electrons in more optimum conductors like copper.
Fig 3.2 Intrinsic silicon
16
Impurity Added Silicon (Extrinsic): P-type and N-type Semiconductors
Extrinsic silicon in a solar cell has added impurity atoms purposefully mixed in with the silicon
atoms, maybe one for every million silicon atoms. Phosphorous has five electrons in its outer
shell. It bonds with its silicon neighbor atoms having valency of 4, but in a sense, the
phosphorous has one electron that doesn't have anyone to bond with. It doesn't form part of a
bond, but there is a positive proton in the phosphorous nucleus holding it in place. When
energy is added to pure silicon, in the form of heat, it causes a few electrons to break free of
their bonds and leave their atoms. A hole is left behind in each case. These electrons, called
free carriers, then wander randomly around the crystalline lattice looking for another hole to
fall into and carry an electrical current. In Phosphorous-doped Silicon, it takes a lot less energy
to knock loose one of "extra" phosphorous electrons because they aren't tied up in a bond with
any neighboring atoms. As a result, most of these electrons break free, and release a lot freer
carriers than in pure silicon. The process of adding impurities on purpose is called doping, and
when doped with phosphorous, the resulting silicon is called N-type ("n" for negative) because
of the prevalence of free electrons. N-type doped silicon is a much better conductor than pure
silicon. The other part of a typical solar cell is doped with the element boron, which has only
three electrons in its outer shell instead of four, to become P-type silicon. Instead of having free
electrons, P-type ("p" for positive) has free openings and carries the opposite (positive) charge
Formation of Potential Barrier and Photoelectric Effect
The electric field is formed when the N-type and P-type silicon come into contact. Suddenly,
the free electrons on the N side combine the openings on the P side. Right at the junction, they
combine and form something of a barrier, making it harder and harder for electrons on the N
side to cross over to the P side (called POTENTIAL BARRIER). Eventually, equilibrium is
reached, and an electric field separating the two sides is set up. This electric field acts as a
diode, allowing (and even pushing) electrons to flow from the P side to the N side, but not the
other way around. It's like a hill -- electrons can easily go down the hill (to the N side), but
can't climb it (to the P side).
When light, in the form of photons, hits solar cell, its energy breaks apart electron-hole pairs
(Photoelectric effect). Each photon with enough energy will normally free exactly one electron,
resulting in a free hole as well. If this happens close enough to the electric field, or if free
electron and free hole happen to wander into its range of influence, the field will send the
17
electron to the N side and the hole to the P side. This causes further disruption of electrical
neutrality, and if an external current path is provided, electrons will flow through the path to
the P side to unite with holes that the electric field sent there, doing work for us along the way.
The electron flow provides the current, and the cell's electric field causes a voltage.
Fig 3.3 Formation of potential barrier
Silicon is very shiny material, which can send photons bouncing away before energizing the
electrons, so an anti reflective coating is applied to reduce those losses. The final step is to
install something that will protect the cell from the external elements- often a glass cover plate.
PV modules are generally made by connecting several individual cells together to achieve
useful levels of voltage and current, and putting them in a sturdy frame complete with positive
and negative terminals.
18
3.5 EMERGENCE OF PEROVSKITE SOLAR CELLS
Metal halide perovskites (MHPs) have attracted intensive attention as promising photovoltaic
materials during the last few decades. The term of “Perovskite” is employed to describe a class
of materials with the same crystal structure as the mineral calcium titanate (CaTiO3), which
was firstly discovered in the Ural Mountains of Russia in 1839 and named after Lev Perovski, a
renowned Russian mineralogist (Chakhmouradian and Woodward, 2014). Now, MHPs have
developed into a broad range of materials with the general formula ABX3, where A and B are
monovalent and divalent cations, respectively and X stands for anions. Besides, MHPs have
been widely used as active materials in various optical and electronic applications, such as
photovoltaic devices (PV) , light-emitting diodes, photodetectors, lasers , sensors , biomedicine,
etc.
The first demonstration of the photovoltaic effect on perovskite materials dates back to 2009 by
Miyaska and his co-works, but the power conversion efficiency (PCE) was only 3.8%.
Although the performance of perovskite solar cells (PSCs) was low at that time, the strong
optical absorption of perovskite materials attracted widespread attention in academic circles.
However, these cells suffered from rapid degradation of perovskite materials in the liquid
electrolyte. In 2012, important breakthroughs in PSCs were realized. In these works, all-solid
device configurations were reported with Spiro-MeOTAD as the hole transport layer to solve
the instability problem in liquid electrolytes. The PCEs of about 10% have been reported with
improved operation stability.
Now, the most recent world record for single-junction PSCs has reached 25.6%, claimed by
researchers at South Korea’s Ulsan National Institute of Science and Technology (UNIST)
(2021). As demonstrated in Figure 3.4, the laboratory efficiency of PSCs is comparable to that
of the first-generation monocrystalline silicon solar cell that takes about 40 years for this level.
In addition, perovskites have been demonstrated as promising candidates in multi-junction cells
due their easily tuneable bandgap.
The state-of-the-art perovskite-on-silicon tandem solar cell has achieved a PCE of 29.52% in
Oxford PV on approximately 30 × 30 cm2 device area. More recently, the all-perovskite
tandem solar cell with a certified efficiency of 26.4% has also been reported. Perovskite
materials are excellent light absorbers with outstanding optoelectronic properties such as high
19
light absorption coefficient, long carrier diffusion length (exceeding 1 mm), low non-radiative
recombination loss and high defect tolerance. The theoretical limit of single-junction PSCs is
about 33%, and that of tandem solar cells can reach over 40%.
Along with ease of accessibility through low-cost solution processes, there is no doubt that
PSCs have become one of the most promising photovoltaic technologies. Since reported in
2009, it was rated as one of the ten scientific breakthroughs by science. Next year, it was
elected as one of the most anticipated scientific and technological breakthroughs by Nature. In
the World Economic Forum of 2016, PSCs were honoured as one of the top 10 emerging
technologies that would break the limitations of silicon-based photovoltaics. In a world,
perovskite materials have become a hot topic in both academic and industrial fields.
Fig 3.4 Progress of cell efficiency in single crystal and multicrystalline Si cells,
perovskite solar cells, perovskite/Si tandem according to Best Research-Cell
Efficiency chart from National Renewable Energy Laboratory.
20
3.6 DEVICE STRUCTURE OF PEROVSKITE SOLAR CELLS
The device structure of PSCs basically contains an absorber layer, an electron transport layer
(ETL), a hole transport layer (HTL), a transparent conductive oxide (anode) and a metal
contact (cathode). The incident light enters through the transparent conductive oxide (FTO or
ITO) towards the perovskite absorber layer. The schematic of the device structure in both nip
structure and pin structure is shown in Figure 3.5 a, b, respectively. The absorber layer upon
absorption of the incident radiation creates electron and hole pairs. These generated electrons
and holes are transported via ETL and HTL, respectively, towards the external circuit with the
help of charge collecting contacts. The material to be used in ETL and HTL must have the
required band alignment with respect to the absorber layer to ensure proper carrier collection.
In order to obtain the best possible performance from the PSC, all three layers of materials
must be wisely selected and fabricated, demonstrated the role of layer thickness and carrier
concentration requirement for all three layers. They revealed that the optimum transport layer
(both ETL and HTL) thickness must be as minimum as possible until it ensures proper film
coverage across the perovskite layer. The optimum absorber layer thickness is equivalent to the
carrier diffusion length of the perovskite.
Fig 3.5. Demonstration of device structure of PSC: (a) n-i-p structure
(b) p-i-n structure
21
The transport layers can employ both organic and inorganic materials. The organic HTLs
require extremely high purity and cost. The widely used HTL Spiro-OMeTAD costs are ten
times higher than Platinum and Gold. Moreover, certain studies suggest that the organic HTLs
actively participate in the process of degradation, which contributes to the poor stability of
PSCs. The future development of PSCs requires a wise selection of the HTL. The inorganic
HTLs seem to be a potential alternative. The inorganic P-type semiconductor such as
nanotubes, nanocrystal, quantum dots and nano powder contributes towards the increment of
the performance of the PSCs. The inorganic HTLs are low cost and easy to synthesize with
better stability. An appropriate energy level matching is required with perovskite before
selecting any particular material.
The key points to be considered while selecting an appropriate material for HTL are: (i) the
highest occupied molecular orbital (HOMO) energy level in inorganic p-type semiconductor
should be at a proper position with respect to the valence band of the perovskite layer to enable
proper charge transport and hole collection for better obtaining better current density; and
(ii)there must be less special contact between perovskite and HTL to reduce the carrier
recombination as it reduces the open circuit voltage (Voc) of the cell. Various materials that
can be used as inorganic HTLs are: graphene oxide (GO), carbon (C), Copper thiocyanate
(CuSCN), Copper Zinc Tin Sulfide (CuZnSnS2), Copper indium disulfide (CuInS2), Copper
iodide (CuI), Cuprous oxide (Cu2O), Cupric oxide (CuO), Nickel oxide (NiO) and a few more.
Figure 3.6 exhibits the efficiency tree of PSC using different materials at HTLs.
The ETL layer also contributes significantly to the PCE and device stability. The most widely
used ETL is Titanium dioxide (TiO2), due to its superior stability. However, the fact that it
requires high annealing temperature and assists the process of ion immigration leading
degradation of the cell urges to find an alternative. Various ETL materials are ZnO, CdS, SnO2,
PCBM, etc. Currently, the most popular ETL material is SnO2 due to its wide bandgap 3.6 4.1 eV with deeper conduction band (CB) than TiO2. It is the most potential ETL due to:
(i)higher mobility 240 cm2 /V, (ii) deeper CB leading to enhanced collection and
transportation of charge carrier, (iii) wider bandgap, (iv) low temperature fabrication and (v)
high optical transmittance and conductivity.
22
A transparent conductive electrode (TCE) is the key component for the working of a solar cell
as it not only passes the incident radiation towards the absorber layer but also it extracts the
photo-generated charge carriers towards the external circuit. Proper transparency and
conductivity are the key features of TCEs. There must be a proper balance between
transparency and conductivity for an efficient TCE. The selection of an appropriate TCE is
important and is determined by a parameter called Figure of Merit (FOM).
Fig 3.6. (a) The efficiency improvement tree of perovskite solar cell using
different hole transporting layers. (b) Device architecture and molecular
structure of commonly used hole transporting materials.
23
CHAPTER- 4
PEROVSKITE FILMS PREPARATION
Perovskite solar cells use more abundant and cost-effective elements and have a simpler
manufacturing process than silicon-based solar cells. The manufacturing of silicon solar cells
involves high temperatures in excess of 1000 °C in a highly evacuated chamber. In contrast,
perovskites can be manufactured using simple wet chemistry, with no requirement for an
evacuated environment. The conditions and techniques used to prepare the perovskite film are
crucial for crystallinity, controlling the performance of the cell. The factors that need to be
strictly controlled have been identified as atmospheric conditions during film growth, reagent
stoichiometry, a method to deposit perovskite on the substrate, annealing temperature/duration,
and additives used. There are three main methods for preparing perovskite films: solution
processing, vapor deposition and hybrid vapor-solution processing.
Fig 4.1. (A) The Dual-source thermal evaporation (B) One-step and two-step solution
process for perovskite film growth. (C)Perovskite film formation through vapor
assisted deposition.
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4.1 Vacuum Deposition
The vacuum deposition method was firstly reported by Mitzi and coworkers, in which organicinorganic compounds were rapidly heated to sublimate, then deposited on the substrate. This
technique allows facile control over the film composition and thickness with high
reproducibility. The perovskite films fabricated by vacuum deposition were proven to be highquality with excellent film uniformity. Although the vacuum deposition requires expensive
equipment, it still holds the advantages of fabricating large-area films without using toxic
solvents. This makes it very promising in the production of the perovskite module. Recently,
vacuum deposition has witnessed further progress in the perovskite’s materials including mixed
halide, narrow-band gap, and formamidine based perovskite solar cells. The champion
efficiency of 21.32% and 18.13% has been reported on the small-size cell and mini-modules
(effective device area 21 cm2), respectively.
4.2 One-Step Solution Deposition
One-step solution deposition is a commonly used method for fabricating perovskite films in
labs. In this method, the precursor solutions are prepared by mixing precursors in solvents such
as N-dimethylformamide (DMF), then spin-coated on the substrates, followed by thermal
annealing to initialize the crystallization. To obtain flat and compact films without pin-holes,
antisolvents are usually used to induce homogeneous nucleation, for example, toluene,
chlorobenzene, or diethyl ether. One-step deposition is simple to conduct in labs and antisolvents can serve as the carriers for Lewis acid and base additives, which has been
demonstrated as an effective strategy for defect passivation. Subsequently, conjugated
polymers dissolved in antisolvents were introduced in perovskite films to reduce trap states and
non-radiative recombination loss.
4.3 Two-Step Solution Deposition
Besides one-step solution deposition, two-step sequential deposition is another commonly
used method to obtain perovskite films with improved reproducibility. PbI2 was spin-coated on
the substrates followed by sequential deposition of MAI, then the formation of the perovskite
was accomplished by thermal annealing. Compared with one-step solution deposition, two-step
deposition has better control over the film morphology by relieving effects from the
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surrounding environment. However, the conversion of PbI2 to the perovskite remains a major
challenge to achieve highly efficient and stable devices The residual PbI2 at the interfaces was
suggested to impede the carrier transportation and induce severe degradation PSCs.
4.4 Vapor-Assisted Deposition
In this method reaction between the as-deposited PbI2 (solid) and MAI vapor was adopted to
obtain perovskite films with full coverage and smooth surface. The vapor-assisted process is a
facile low temperature method with the slowdown in nucleation and film growth, which
delivers increasing grain size and high Reproducibility. In addition, vapor-assisted deposition
provides the possibility of growing high-quality perovskites on curvature or textured substrates.
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CHAPTER- 5
APPLICATIONS
Perovskite solar cells have a wide range of potential applications due to their unique
properties and advantages over traditional silicon-based solar cells. Some of the applications
of perovskite solar cells are:
1. Portable Electronics: Perovskite solar cells can be integrated into portable electronic
devices, such as smartphones and tablets, to extend their battery life and reduce the need
for external charging.
2. Building-Integrated Photovoltaic: Perovskite solar cells can be integrated into building
materials, such as windows, walls, and roofs, to generate electricity and reduce the energy
consumption of buildings.
3. Wearable Electronics: Perovskite solar cells can be integrated into wearable electronic
devices, such as smartwatches and fitness trackers, to provide a sustainable and renewable
source of power.
4. Grid-Scale Power Generation: Perovskite solar cells have the potential to be used in
large-scale power generation applications, such as utility-scale solar farms, to provide
renewable energy to the grid.
5. Off-Grid Power Generation: Perovskite solar cells can be used in off-grid applications,
such as rural electrification, to provide a sustainable and cost-effective source of power in
areas without access to traditional electricity infrastructure.
Overall, these applications demonstrate the potential of perovskite solar cells to provide a
sustainable and renewable source of energy for a wide range of applications, and further
research is needed to optimize their performance and stability for practical use.
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CHAPTER-6
ADVANTAGES AND DISADVANTAGES
6.1 Advantages
Perovskite solar cells have gained considerable attention in the research community in recent
years due to their unique advantages compared to traditional silicon-based solar cells. Some of
the advantages of perovskite solar cells are:
1. High Efficiency: Perovskite solar cells have demonstrated high conversion efficiency,
reaching up to 25.5%, which is comparable to the efficiency of silicon-based solar cells.
2. Low Cost: Perovskite solar cells can be produced at a lower cost compared to traditional
silicon-based solar cells due to the lower cost of raw materials and the simpler
manufacturing process.
3. Flexibility: Perovskite solar cells can be fabricated on flexible substrates, making them
suitable for a wide range of applications, including wearable electronics, portable devices,
and building-integrated photovoltaic.
4. Tunability: The band gap of perovskite solar cells can be easily tuned by adjusting the
composition of the perovskite material, allowing for the fabrication of cells that are
optimized for different parts of the solar spectrum.
5. Environmental Benefits: Perovskite solar cells are more environmentally friendly
compared to traditional silicon-based solar cells as they require less energy to produce and
generate less waste during the manufacturing process.
Overall, these advantages make perovskite solar cells a promising candidate for the next
generation of photovoltaic devices, and further research is needed to improve their stability
and durability for practical applications.
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6.2 Disadvantages
While perovskite solar cells offer a range of advantages over traditional silicon-based solar
cells, they also have several disadvantages:
1. Stability: Perovskite solar cells are prone to degradation in the presence of moisture, heat,
and UV radiation, which can limit their lifetime and performance.
2. Toxicity: Some of the materials used in perovskite solar cells, such as lead, are toxic and
pose a potential health risk during the manufacturing process and end-of-life disposal.
3. Scalability: While perovskite solar cells can be produced using low-cost materials, the
manufacturing process is still relatively complex and difficult to scale up for large-scale
production.
4. Reproducibility: The performance of perovskite solar cells can vary significantly between
batches, making it challenging to reproduce consistent results.
5. Commercialization: The commercialization of perovskite solar cells is still in its early
stages, and there are several technical and economic barriers that need to be addressed before
they can be widely adopted.
Overall, while perovskite solar cells offer many advantages, these disadvantages highlight
some of the challenges that need to be addressed to realize their full potential as a viable
alternative to traditional silicon-based solar cells.
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CHAPTER 7
FUTURE ENHANCEMENT
Perovskite solar cells have shown significant promise as a next-generation solar technology.
However, to enable widespread commercialization, further research is needed to address some
of the key challenges associated with perovskite solar cells. Some potential future
enhancements of perovskite solar cells are:
Stability: The stability of perovskite solar cells needs to be improved to ensure their long-term
reliability and performance. This can be achieved through the development of new materials,
device architectures, and encapsulation strategies that protect the perovskite layer from
degradation.
Efficiency: While perovskite solar cells have already achieved high conversion efficiencies,
further improvements are needed to maximize their performance. This can be achieved through
the development of new materials and device architectures that increase the absorption of light
and reduce the recombination of charge carriers.
Scalability: The scalability of perovskite solar cell production needs to be improved to enable
large-scale manufacturing. This can be achieved through the development of new production
methods that are simple, cost-effective, and scalable.
Toxicity: The use of toxic materials, such as lead, in perovskite solar cells poses potential
health and environmental risks. The development of non-toxic and environmentally friendly
materials for perovskite solar cells could address this issue.
Integration: The integration of perovskite solar cells into existing infrastructure and products,
such as buildings and vehicles, needs to be improved to enable their widespread adoption. This
can be achieved through the development of new integration methods and device architectures.
Overall, these future enhancements of perovskite solar cells demonstrate the potential for this
technology to become a key player in the transition to a sustainable and renewable energy
future, and further research is needed to address these challenges and unlock their full potential.
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CHAPTER 8
CONCLUSION
The importance of generating electricity from renewable sources has highlighted the abundant
solar resources on Earth. Photovoltaic using the photovoltaic effect are currently used to
generate electricity from solar energy. With the increase in solar PV capacity globally,
researchers are focusing on maximizing efficiency and decreasing manufacturing costs of solar
cells. Third-generation solar cells, specifically perovskite solar cells, are in development and
have the potential to dominate the solar PV market in the future. These solar cells have a high
potential to increase efficiency while decreasing production costs.
Perovskite solar cells have great potential in the solar PV market due to their high efficiency.
The unique structural and fundamental features that make perovskite such effective solar cells
have been identified. Despite perovskite solar cells' potential, there are still some major issues
that need to be addressed before large-scale commercialization.
Overall, this report highlights the impressive features of perovskite solar cells along with the
challenges that must be overcome for large-scale commercialization techniques used in labscale projects are not suitable for large-scale production. This is being addressed with a search
for techniques that are compatible with roll-to-roll processing, allowing high throughput.
Therefore, future research should focus on addressing the stability and manufacturing issues of
perovskite solar cells for large-scale commercialization.
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