REVIEW RESEARCH PAPER ON PEROVSKITE SOLAR CELLS AUTHORS Mayur Kinra Saksham Goyal Mahima Dahi Deepak Singh Dhruv Bhatia BATCH 2016 CSC 1

REVIEW RESEARCH PAPER ON

PEROVSKITE SOLAR CELLS

AUTHORS

Mayur Kinra

Saksham Goyal

Mahima Dahi

Deepak Singh

Dhruv Bhatia

BATCH 2016 CSC

1. ABSTRACT
“The light from the Sun is a non-vanishing sustainable wellspring of vitality which is free from
ecological contamination and commotion. The creation of solar cells has gone through a
substantial number of change ventures starting with one age then onto the next. Silicon-based
sunlight based cells were the original sun based cells developed on Si wafers, for the most part
single gems. Promote improvement too thin movies, color sharpened sunlight based cells, and
natural solar cells upgraded the cell productivity. The advancement is essentially obstructed by
the cost and productivity.
The authors have reviewed the already existing work in the field of Perovskite Solar Cells. A
perovskite solar cell is a type of solar cell which includes a perovskite structured compound,
most commonly a hybrid organic-inorganic lead or tin halide-based material, as the light-
harvesting active layer. The structure, solar cell architecture, preparation methods of perovskite
solar cells have been reviewed.”

2. INTRODUCTION
“Present day solar cells incorporate fluid inks, upconversion, light retaining colors, quantum
specks, natural/polymer sunlight based cells, versatile cells and perovskite sun based cells.
Among these top researches perovskite solar cell stands as a distinct category called emerging
photovoltaics. These photovoltaics solar cells have a place with the class of the third era which
incorporates numerous thin film advancements.” The first and second era solar cells
incorporate silicon wafers and thin film innovations individually, which are lesser execution
and exorbitant cost. The organometallic halide light engrossing arrangement of perovskite solar
cell made it as higher power change effective alongside low material expenses.

Figure 2.1: Crystal lattice of the methylammonium lead halide (CH3NH3- PbX3) perovskite structure.

The general formula for perovskite materials is ABX3. In this arrangement,6 ‘X’ (Anion with
Miller Indices:1/2,1/2,0) the ‘A’ (Large Cation with Miller Indices:1/2,1/2,1/2) and ‘B’ (Small
cations with Miller Indices:0,0,0) coordinate with 12, forming octahedral and cuboctahedra
geometries, respectively.
Solar cell technologies which are silicon based offers a combination of properties like high
temperature stability, low cost, ease of surface passivation and hardness have made themselves
fascinated in applications of photovoltaics.

3. GENERATIONS OF SOLAR CELLS
3.1 For the most part, first era’s solar cells incorporate
3.1.1 Single Crystal Solar Cell
3.1.2 Multi Crystal Solar Cells.
“This is the most seasoned and the most usually utilized innovation because of high
efficiencies. First generation solar cells are produced on wafers.” Every wafer can supply 2-3-
watt power. “They vary in their crystallization levels. On the off chance that the entire wafer
is just a single precious stone, it is called single crystal solar cell. On the off chance that wafer
comprises of crystal grains, it is known as the multi-crystal solar cell. Anybody can see the
limits between grains in the solar cell. Even though the proficiency of monocrystal solar cells
is higher than multi-crystal solar cells, generation of a multi-crystal wafer is less demanding
and less expensive. In this way, they are focused with monocrystals.

3.2 Second generations solar cells focused on
3.2.1 a-Si thin film solar cells
3.2.2 mc-Si solar cells
3.2.3 CdTe solar cells
3.2.4 CIS and CIGS solar cells.
Their efficiencies are less than first generation, their costs are also less than first generation.
These thin films can also be grown on flexible substrates. As an advantage of thin film solar
cells, they can be growth on large areas up to 6 m2. However, wafer based solar cell can be
only produced on wafer dimensions.
The second-generation solar cells include amorphous Si (a-Si) based thin films solar cells,
Cadmium Telluride/Cadmium Sulphide (CdTe/CdS) solar cells and Copper Indium Gallium
Selenide (CIGS) solar cells.

3.3 Third Generation solar cells considers
3.3.1 Nanocrystal based solar cell
3.3.2 Polymer based solar cells
3.3.3 Dye sensitized solar cells
3.3.4 concentrated solar cells
“These are the novel advancements which are promising however not economically
demonstrated yet. Most grew third era sunlight based cell writes are color sharpened and
thought sun based cell. Color sharpened Dye-sensitized cells (DSSC) depend on color particles
between terminals. Electron opening sets happen in color particles and transported through
TiO2 nanoparticles. Although their productivity is low, their cost is likewise low. Their
creation is simple concerning different advancements. Concentrated PV solar cell is another
promising innovation. The primary rule of concentrated cells is to think a substantial measure
of radiation from the sun on to a little area where the PV cell is found. The measure of
semiconductor material, which may be extremely costly, is decreased along these lines. In this
framework, an impeccable optical framework ought to be coordinated.” Focus levels begins
from 10 suns to a great many suns. “In this way, add up to cost can be lower than regular
frameworks. CPVs are promising innovations for not so distant future.

4. HISTORY OF PEROVSKITE SOLAR CELLS

4.1 First real perovskite solar cell was developed in 2012 by replacing dyes by
organic/inorganic lead halide in Dye Synthesised solar Cells.
DSC:

Figure 4.1: Dye synthesised perovskite solar cell structure.

Liquid electrolyte was replaced with HTM (Hole Transport Material) to make solid state DSC
but to increase their efficiency thick mesoporous layer is required for absorption which
increases hole transport resistance and recombination.
“4.2 Quantum dot solar cells: Used semiconductor nanocrystals as light absorbers.
4.3 In 2012 perovskite solar cells resulted efficiency of 10% in solid state configuration using
CH3NH3PbX3 where X is a halogen.
4.4 Recently perovskite solar cells with 15% efficiency have been reported with target of 20%
efficiency.”

Figure 4.2: Progress in perovskite solar cell efficiency.

5. PROCESSING PEROVSKITE SOLAR CELLS
“Traditional silicon solar cell processing is quite expensive, a multistep process which requires
high temperature and vacuum facilities in special clean rooms to produce high purity silicon
wafers whereas, and perovskite solar cell processing is simple and cost effective. There are
two methods of processing of these solar cells which are variety of solvent techniques and
vapour deposition techniques.”
5.1 Solution Process Technique
“In solution process technique the deposition of CH3NH3PbI3 perovskite on a mesoporous
Tio2 substrate takes place in two methods that is, one step and two step coating methods. In
one step coating method CH3NH3I and PbI2 are dissolved in appropriate protic solvent
gamma-butyrolactone (GBL) or dimethyl sulfoxide(DMSO) and this applied as coating
solution, the processes like drying and annealing are followed by spin coated methods.
In two step coating method to the TiO2 substrate PbI2 solution is coated first to form PbI2 film
and then 2-proponol solution of CH3NH3I is added to spinning PbI2 film.”

Figure 5.1: Flow of solution process technique

To get high quality perovskite film, it is important to adjust coating parameters like
temperature, time, spinning rate, viscosity, solution wettability etc.

5.2 Vapour Assisted Solution Process (VASP)
This method is not quite the same as the arrangement procedure and vacuum statement, by
maintaining a strategic distance from co-affidavit of inorganic and natural species. It exploits
the dynamic reactivity of CH3NH3I and thermodynamic solidness of perovskite amid the in-
situ development process and furnishes films with very much characterized grain structure with
grain sizes up to microscale, little surface harshness and full surface scope, reasonable for PV
applications. Gadgets in view of movies arranged from vapor helped arrangement process
accomplished a best power transformation proficiency of 12.1%, so far, the most noteworthy
effectiveness of CH3NH3PbI3 with planar structure.

Figure 5.2: Flow of vapour assisted solution process

“The issue with warm dissipation system is it requires high vacuum condition which leads to
costlier conditions and confines large-scale manufacturing. This issue can be settled with vapor
helped strategy though turn covered lead halide is toughened within the sight of methyl iodide
vapor at 150oc temperature for adaptable activity. The multi-stacked thin movies are acquired
over a vast zone which is pertinent for generation of multi intersection cells.”

6. PEROVSKITE SOLAR CELLS ARCHITECTURES

“The huge interest of CH3NH3PbI3 perovskite does not only lie in the high efficiencies but also
in the novel configurations made possible by the singular characteristics of the material.

Contingent on the part of Perovskite material in the gadget and the idea of the anodes utilized
(best and base) Perovskite sun oriented cells engineering will be chosen. Essentially perovskite
is a light retaining layer, for the most part perovskite is worked around color sharpened Dye
Synthesized Solar cell (DSSC) design. Positive charges are removed by the straightforward
base terminal (cathode), which is dominatingly be isolated into ‘sharpened’ and charge transport
happens in thin-film, lion’s share opening or electron transport happens in the greater part of
the perovskite itself.” Like the sharpening in color sharpened sun oriented cells, the perovskite
material is covered onto a charge-directing mesoporous framework most regularly TiO2 – as
light-safeguard. The created electrons are exchanged from the perovskite layer to the
mesoporous TiO2 sharpened layer through which they are transported to the cathode and
extricated into the outside circuit.
Figure 6.1: Basic layout of perovskite solar cell

Figure 6.2: charge generation and extraction of sensitized and thin film perovskite solar cell.

7. PROGRESS REPORT OF PEROVSKITE SOLAR CELLS

7.1 First perovskite solar cell was formed by Miyasaka in 2009, it was based on DSC
architecture and had efficiency of 3.9%. which was increased to 6.8% in 2011 by
park.
7.2 Major achievement in 2012, Henry Snaith and Mike Lee from the University of
Oxford made perovskite with a solid-state hole transporter such as spiro-OMeTAD.
This gave efficiency of 10%.
7.3 In 2013 it was realised PSC is possible without TiO2, because perovskite can act as
both absorber and Electron/hole transporter.
7.4 In Several researches on techniques for making PSC resulted in increased
efficiency to 15%.
7.5 Docampo and co-workers build first inverted architecture solar cell.
7.6 Different research institutions working on PSC have achieved high efficiency solar
cells, maximum being 22.1%.

8. CURRENT RESEARCH WORK IN FIELD OF PEROVSKITE
SOLAR CELLS
PSCs are prone to degradation by different agents. Typically, PSCs are susceptible to the
following four factors: oxygen and moisture, UV light, solution process (solvents, solutes,
additives), and temperature. To combat this several researches has been done:

8.1 “To improve stability against water:
Firstly, due to the high sensitivity of CH3NH3PbI3 to water, it tends to hydrolyse in the
presence of moisture, leading to the degradation of perovskite occurs as followings:
CH3NH3PbI3 (s) ? PbI2 (s) + CH3NH3I (aq)
CH3NH3I (aq) ? CH3NH2 (aq) + HI (aq)
4HI (aq) + O2 (g) ? 2I2 (s) + 2H2O (l)
2HI (aq) ? H2 (g) + I2 (s)
“It should be noted that the moisture, oxygen, and UV radiation is indispensable for the
degradation process. Perovskite using aprotic organic anion (CH3)4N+, so that water which is
Lewis base i.e. water cannot take proton.”
Hybrid Perovskite: CH3NH3Pb(I1-xBrx)3 which performs better against humidity.

“Most recently, Yang and collaborators found a huge wonder that when they manufactured
their perovskite sunlight based cells in controlled dampness conditions, control change
productivity is helped to the most elevated proficiency of 19.3% of a planar geometry. They
proposed a remaking component prompted by dampness. The hygroscopic natural species
could be broken up by dampness. In this way the chemicals transport in the film will be
quickened. Three phases of stage change of perovskite from PbI2 to a blend of CH3NH3PbI3
and CH3NH3PbCl3, lastly to CH3NH3PbI3 as well as CH3NH3PbI3-xClx were checked from
the XRD and SEM comes about. Be that as it may, after the gadgets were manufactured,
regardless they experienced the dampness. The power change productivity held under 5% of
the first execution following 6 days put away in the encompassing environment.”

8.2 To improve stability against UV Radiation:
“Hitoshi and co-workers found that after the light exposure for 12 h, the original layer of
CH3NH3PbI3 turned into PbI2, evidenced by the decreased Vis absorption and XRD

patterns.30 They proposed a possible mechanism to explain the degradation process in the film
under light exposure as followings:”
2I- ? I2 + 2e
3CH3NH3 + ? 3CH3NH2 ? + 3H
I – + I2 + 3H+ + 2e- ? 3HI ?
By Snaith & co-workers: Avoidance of encapsulation in Nitrogen adding UV-filters in front
of TiO2 “.
As a typical n-type semiconductor, many oxygen vacancies are located at the surface of TiO2
particles. These electron-donating sites could combine with oxygen, which adsorbs to the
oxygen vacancy sites.
After UV illumination, an electron-hole pair will form on TiO2 and the hole in the valence
band could combine with the electron at the oxygen adsorption site.

8.3 To improve Chemical stability:
For the perovskite film development, distinctive strategies have been created, for example,
arrangement process, vapor testimony process, and vapor-helped arrangement process.
Contrasted with vapor affidavit process, arrangement process gives straightforward and simple
techniques, minimal effort, and flexible parts in the movies. In this way, the greater part of the
scientist’s centre around the advancement of arrangement process for perovskite manufacture.

• Recent research on PSC suggested degradation of perovskite by certain essential
production chemicals, as a result counter chemical are being studied upon.
• For eg: Introduction of MMT(montmorillonite) as buffer layer in PSC to reduce
corrosion by TBP(4-tert-Butylpyridine).

9. OUTCOME OF OSCAR RESEARCH ON PEROVSKITE SOLAR
CELLS
OSCAR: Optical Sensors based on Carbon materials
Experiment which demonstrated for the first time organic-based solar cell operation in
extra-terrestrial conditions.
Because of a one of a kind arrangement of characteristic properties (i.e. high power,
tuneable assimilation window, adaptability, foldability) in mix with preparing conceivable
outcomes in space, natural and perovskite sun oriented cells have the capability of turning

into a troublesome innovation for photovoltaic vitality age in space applications. With the
dispatch of the stratospheric mission OSCAR, natural based sun oriented cells where tried
in situ in additional earthbound conditions out of the blue.
An arrangement of HOPV gadgets survived 3 hours of stratospheric flight. This exploratory
outside debasement contemplate in close space condition affirms that, on a fundamental
level, natural and perovskite sun oriented cells are suitable supplements for space sun
oriented vitality gathering.
A move of worldview could occur, for which a segment of the examination exertion now
devoted to the long-haul adjustment of sun based cells against oxidizing operators may
stray towards understanding the degree of debasement presented by outrageous temperature
cycling, high vitality episode charged particles, mechanical “siege” and low weights.
Because the idea of the charge transport in natural semiconductors, we imagine the
extraordinary temperatures to be the most sensitive instance of study, potentially prompting
a lot of materials to be unfit for low/high temperature activity.
Taking everything into account, the street to stroll towards this new vision is long and still
inconceivably unexplored, which leaves abundant space for future investigations.

Figure 9.1: Solar cell mounting structure, and schematics of the flight altitude.

10. SUMMARY AND FUTURE SCOPE

In current research silicon solar cell is recorded with productivity of 25% however it is costly
to make of such high proficiency cells and typical solar cell installations are around 15%
efficient.
Perovskite solar cells are recorded with 26% proficiency with low handling expense and high
stable qualities whereas, second era thin film innovation brings about 12-20% effective
relatively. The perovskite propelled material is very easy to create and simple to make by
means of printing process depending on fluid forerunner.

To catch diverse parts of light ranges perovskite materials can be effectively tuned and cost of
creation of such super productivity sun oriented cells will in the long run get lessened.

• FUTURE SCOPE

10.1 Solving ambiguous measurement of current voltage observations:
This is due to hysteretic behaviour: depending on scanning conditions, though there are various
proposed origins for hysteric behaviour but bit exact reason is not yet discovered.
10.2 Eliminating Lead from PSC: Lead is a toxic metal which is hazardous to
humans,
Therefore, its necessary to replace lead.
Possible alternative for this is Sn2+ but it gets easily oxidised to Sn4+ resulting in lower
efficiency. Finding alternatives will be easy in PSC because PSC is structure based technology.
10.3 Increasing efficiency by structural modifications and forming tandem
structures.
10.4 For commercialization, environmental and photo-stabilities should be
guaranteed. For this to be achieved, encapsulation technology and materials with
humidity-resistance and photo-stability must be developed.
10.5 Power Application in smart windows, which gives tinted glass and generate
power simultaneously.