EFFICIENCY IMPROVEMENT ON SOLAR CELL

USING ZINC OXIDE ANTI REFLECTIVE

COATING

A PROJECT REPORT

Submitted by

AJITH D (1516002)
BOOPATHI T (1516019)
DHANUSHKUMAR N (1516020)
DHILIP J (1516021)

in partial fulfilment for the award of the degree

of

BACHELOR OF ENGINEERING

in

MECHANICAL ENGINEERING

K.S.R. COLLEGE OF ENGINEERING

(An Autonomous Institution, Affiliated to Anna University Chennai and Approved by AICTE)

TIRUCHENGODE-637215
APRIL 2019
 K.S.R COLLEGE OF ENGINEERING
TIRUCHENGODE-637215
ANNA UNIVERSITY, CHENNAI

BONAFIDE CERTIFICATE

Certified that this project report “EFFICIENCY IMPROVEMENT ON SOLAR

CELL USING ZINC OXIDE ANTI REFLECTIVE COATING” is the
bonafide work of AJITH D (1516002), BOOPATHI T (1516019), DHANUSH
KUMAR N (1516020), DHILIP J (1516021) who carried out the project work
under my supervision.

SIGNATURE SIGNATURE

Dr. N. SHIVASANKARAN, Ph.D., Dr. N. SHIVASANKARAN, Ph.D.,

HEAD OF THE DEPARTMENT SUPERVISOR

Department of Mechanical Engineering, Department of Mechanical Engineering,

K.S.R.College of Engineering, K.S.R.College of Engineering,
Tiruchengode – 637215. Tiruchengode – 637215.

--------------------------------------------------------------------------------------------------------------------------------

Submitted for Project viva-voce held on ……………………………

Internal Examiner External Examiner

i
 ACKNOWLEDGEMENT

We feel highly honored to extend our sincere gratitude to our beloved Founder-
Chairman, Lion Dr.K.S.RANGASAMY, MJF K.S.R Educational Institution and our
Chairman Mr.R.SRINIVASAN, B.B.M., MISTE, Aarthi Educational Charitable trust for
providing all facilities to complete this project work.

We wish thank our respected principal Dr.P.SENTHILKUMAR M.E., Ph.D.,

K.S.R COLLEGE OF ENGINEERING, Tiruchengode for his valuable support
completion of the project.

We feel highly elated to thank our respectable head of the Department

Dr.N.SHIVASANKARAN, Ph.D., who guided us and was a pillar of support for the
successful completion of the project.

It is a pleasure to express our gratefulness to our beloved parents for providing their
support and confidence to us for the completion of the project and our heartfelt thanks to
our entire department faculty members, beloved friends, directly and indirectly who
helped us during the work of the project.

ii
 ABSTRACT

Several researchers had improved the solar cell efficiency by film-forming

techniques such as spin coating, doctor blading and casting process. In this project, ZnO

Nano particle is synthesized and coated as a thin film over a polycrystalline solar cell. The

ZnO layers were found to be an excellent antireflection coating (ARC), exhibiting

exceptional light trapping at wavelengths ranging from 400 to 1000 nm because of their

lowest effective reflectance. In the current paper, ZnO ARC layers are coated over the

thin glass film using dip coating and spin coating process. Due to anti-reflective property,

it increases the efficiency of solar cell to 2% to 5% and offer a promising technique to

produce high-efficiency, low-cost solar cells.

iii
 CONTENTS

CHAPTER NO TITLE PAGE NO

ABSTRACT

1 INTRODUCTION 1

1.1 INTRODUCTION 2

2 LITERATURE REVIEW 3

2.1 LITERATURE REVIEW 4

3 METHODOLOGY 8

3.1 SELECTION OF MATERIAL 9

3.1.1 PROPERTIES OF ZINC OXIDE 10

3.1.2 STRUCTURE OF ZINC OXIDE 10

3.2 SYNTHESIS OF NANO 11

STRUCTURED ZnO THIN FILM

3.2.1 PHYSICAL METHOD 12

3.2.2 CHEMICAL METHOD 12
3.3 ANTI REFLECTION COATING 13
3.3.1 DIP COATING METHOD 14
3.3.2 SPIN COATING METHOD 15
3.3.3 RF SPUTTERING METHOD 17

4 RESULT AND DISCCUSSION 20

4.1 MATERIAL MORPHOLOGY 21

4.2 BAND GAP CALCULATION 23

iv
 4.3 EFFICIENCY GRAPH 25

4.3.1 DIP COATING GRAPH 25

4.3.2 RF SPUTTERING GRAPH 26

5 CONCLUSION 28

5.1 CONCLUSION 29

6 REFERENCE 30

6.1 REFERENCE 31

v
 LIST OF TABLES

TABLE NO TABLE DESCRIPTION PAGE NO

3.1.1 PROPERTIES OF ZINC OXIDE 10

vi
 LIST OF FIGURES

FIG NO FIGURE DESCRIPTION PAGE NO

3.1.2 STRUCTURE OF ZINC OXIDE 11

3.2 THIN FILM DEPOSITION 13

3.3.1 DIP COATING METHOD 15

3.3.2 SPIN COATING METHOD 16

3.3.3 RF SPUTTERING METHOD 19

4.1.1 SEM IMAGE OF ZINC OXIDE AT 300NM 22

4.1.2 SEM IMAGE OF ZINC OXIDE AT 200NM 22

4.1.3 SEM and EDAX image of ZnO nano particle 22

4.3.1 DIP COATING EFFICIENCY GRAPH 25

4.3.2 RF SPUTTERING EFFICIENCY GRAPH 27

4.3.3 SOLAR CELL 27

vii
 CHAPTER – 1
INTRODUCTION

1
1.1 INTRODUCTION

In today’s world of growing energy needs and raising environmental concerns

alternatives to the source of energy is very much essential. One such sources of alternative

is solar energy, making use of this energy we can serve the nation with clean and pollution

free energy. Hydrogen and Helium gases are source fuel for the sun. An enormous amount

of energy is released in the form of Light and Heat when the special reaction called

nuclear fusion reaction of Hydrogen gas is burned inside the Sun. The Sun is an enormous

ball of burning gases and it is a Star. Every second, 600 million tons of hydrogen is being

converted into helium. This reaction releases a tremendous amount of heat and energy.

The International Energy Agency has said that solar energy can make considerable

contributions to solving some of the most urgent problems the world faces now.

The development in solar energy technologies will give long term benefits

and affordable, inexhaustible and clean energy to the world. In this project we dealt

with improving this solar energy trapping efficiency by applying a thin film of

coating over the light trappers called Solar cells. The solar cell is device which

converts photons from sunlight into electricity. This phenomenon of conversion of

electricity is called Photovoltaic effect. On application of coating over the solar cells

shows significant improvement in light trapping capacity even in low light.

2
 CHAPTER – 2

LITERATURE REVIEWS

3
2.1 LITERATURE REVIEW

Salman (2012) has coated Zinc oxide (ZnO) film on a porous silicon (PS) layer

using a radio frequency sputtering system while the PS layer was prepared by a photo

electrochemical etching method. The ZnO/PS layers were found to be an excellent

antireflection coating (ARC), exhibiting exceptional light trapping at wavelengths ranging

from 400 to 1000 nm because of their lowest effective reflectance. This, in turn, leads to

increase the efficiency of solar cell to 18.15%.

Kim and Chung et al. (2019) compared a spin-coated ZnO NP buffer layer and RF

magnetron-sputtered ZnO buffer layer for use as the buffer layers of IPSCs. Electrical,

optical, structural, and morphological properties of RF magnetron-sputtered ZnO film and

solution-processed ZnO Nano particle (NPs) buffer film on ITO cathodes was evaluated.

Also electrical, optical and morphological properties were studied on the ZnO sputtered

organic solar cell.

Hwan Wang et al. (2012) the efficiency of flexible polymer solar cells with well-

ordered nano-patterned IZO anode was successfully increased through a simple nano-

imprint process based on a PCDTBT/PC 70 BM BHJ active layer. The flexible nano-

patterned IZO anode was produced with UV-curable poly (urethane acrylate) resin-coated

film on the polycarbonate (PC) substrate. The flexible solar cells with regular nano-

patterned structure exhibited improved light absorption and improved short circuit current

( J sc ). The overall power conversion efficiency (PCE) (%) increased from 3.0% to 3.9%

compared to a device without a Nano-patterned substrate.

4
 Chen and Sun (2010) an anti-reflection (AR) layer is a type of coating applied to

the surface of a material to reduce light reflection and to increase light transmission.

These AR layers are also in the solar cell, planar displays, glasses, prisms, videos, and

camera monitors for reduced reflection of light. The light harvest Efficiency of the poly-Si

solar cells was improved by over 30% with the AR layers.

Chen (2001) the anti-reflection coating made by sol-gel method was reviewed and

studied. Silicon solar cells have a high refractive index which leads to a solar-averaged

reflectance of about 36%. This large reflection loss can be significantly reduced by

coating the silicon with an AR coating. A spray able TiO2 AR coating was developed by

Tracy et al. [33] for solar cells. The coating solution is composed of hydrolysable titanium

compound in inert diluent (e.g. n-butyl acetate), lower aliphatic alcohol (e.g. IPA), and 2-

ethyl-I-hexanol to improve the wetting of coating solution to substrate. The solution is

sprayed onto the substrate to obtain a film thickness of approximately 70nm and a

refractive index of 2.0-2.2, after firing. The heat treatment temperature used for this TiO 2

layer is 350-500 0C, without affecting the performance of solar cell.

Han et al. (2009) the solar cell is coated with anti-reflecting PVC Film layer

through hot embossing method. A solar cell with a patterned PVC film acts as a protective

layer exhibited higher quantum efficiency and total conversion efficiency than a solar cell

with a bare PVC film as a protective layer.

Aziz et al. (2011) coated the solar cell with anti-reflection layer to improve the

efficiency. Anti-reflection coatings of solar cells have been fabricated using different

5
techniques. The techniques used include SiO2 thermal oxidation, ZnO/TiO2 sputtering

deposition and porous silicon prepared by electrochemical etching. The reduction of

reflectivity is a very important parameter in obtaining high efficiency solar cells. To

achieve this goal, the top surface of the solar cells is usually covered with different

antireflection coating methods. These methods can be divided into three techniques:

thermal oxidation, sputtering deposition and electrochemical etching. This technique

attributes to reduction in optical losses and decreases the recombination losses on surface

which lead to increase in the efficiency.

Jannat et al. (2016) the preparation, characterizations and the antireflection (AR)

coating application in crystalline silicon solar cells of sol–gel derived SiC–SiO2 nano

composite. The prepared SiC–SiO2 nano composite was effectively applied as AR layer

on p-type Si-wafer via two step processes, where the sol–gel of precursor solution was

first coated on p-type Si-wafer using spin coating at 2000 rpm and then subjected to

annealing at 450 ◦C for 1 h. The fabricated crystalline Si solar cell with SiC–SiO2 nano

composite AR coating showed comparable power conversion efficiency of 16.99%. New

and effective sol–gel derived SiC–SiO2 AR layer would offer a promising technique to

produce high performance Si solar cells with low-cost.

6
 CHAPTER – 3
METHODOLOGY

7
3.1 SELECTION OF MATERIAL

In this project, we used a Zinc Oxide material as anti-reflective coating in powder

form. Zinc Oxide is an inorganic compound and it is insoluble in water. Its chemical

formula is ZnO and it looks like an white powder. This ZnO is used as an additive in

numerous materials and products including rubbers, plastics, ceramics, glass, cement,

lubricants, paints, ointments, adhesives, sealants, pigments, foods, batteries, ferrites, fire

retardants, and first-aid tapes. Zinc oxide occurs naturally as a mineral Zincite.

Zinc oxide is a wide band gap semiconductor and it belongs to a group of II-VI

semiconductor group. This ZnO semiconductor has several favourable properties,

including good transparency, high electron mobility, wide band gap, and strong room-

temperature luminescence. Those properties are valuable in emerging applications for:

transparent electrodes in liquid crystal displays, energy-saving or heat-protecting

windows, and electronics as thin-film transistors and light-emitting diodes.

ZnO forms cement-like products when mixed with a strong aqueous solution

of zinc chloride and these are best described as zinc hydroxyl chlorides. This cement was

used in dentistry. Zinc oxide also has antibacterial and deodorizing properties. For this

reason it is employed in medical applications such as in baby powder and creams to treat

conditions such as diaper rash, other skin irritations and even dandruff. Due to its

reflective properties it is also used in sun block’s and can often be seen on the nose and

lips of lifeguards at the beach.

8
 PROPERTIES
Chemical formula ZnO
Molar mass 81.38 g/mol
Appearance White Solid
Meting point 1,975 °C (3,587 °F; 2,248 K)
(decomposes)
Boiling point 1,975 °C (3,587 °F; 2,248 K)
(decomposes)
Solubility in water 0.0004 % (17.8 °C)
Band gap 3.3 eV
Refractive index(nD) 2.0041

3.1.1 PROPERTIES OF ZINC OXIDE

3.1.2 STRUCTURE OF ZINC OXIDE

Zinc oxide crystallizes in two main forms, hexagonal wurtzite and cubic zinc

blende. The wurtzite structure is most stable at ambient conditions and thus most

common. The zinc blende form can be stabilized by growing ZnO on substrates with

cubic lattice structure. In both cases, the zinc and oxide centers are tetrahedral. ZnO is a

relatively soft material with approximate hardness of 4.5 on the Mohs scale. Its elastic

constants are smaller than those of relevant III-V semiconductors, such as GaN. The high

heat capacity and heat conductivity, low thermal expansion and high melting temperature

9
of ZnO are beneficial for ceramics. The E2 optical phonon in ZnO exhibits an unusually

long lifetime of 133 ps at 10 K.

Among the tetrahedral bonded semiconductors, it has been stated that ZnO has the

highest piezoelectric tensor, or at least one comparable to that of GaN and AlN. This

property makes it a technologically important material for

many piezoelectric applications, which require a large electromechanical coupling.

3.1.2 STRUCTURE OF ZINC OXIDE

3.2 SYNTHESIS OF NANO STRUCTURED ZnO THIN FILM

Nanotechnology becomes much more popular nowadays. Scientists believe that

by engineering material sizes into nano scale will have an enhancement on properties of

the material. These nano particles have increased strength, higher chemical reactivity and

conductivity when compared to the same materials without nano scale features. They
10
might behave differently when compared to their bulk counterparts. In many literatures, it

can also be learned that nano ZnO offers better performance compared to that of in bulk

size.

There have been many methods to synthesize nano structured ZnO thin films.

There are basically two broad areas of synthesis techniques for nano structured thin films

namely physical methods and chemical methods. The classification of most common

deposition techniques are given below. Each of the below methods has its own merits and

demerits.

3.2.1 PHYSICAL METHOD

Several physical methods are currently in use for the synthesis and commercial

production of nano structured materials. The physical vapour deposition technique

involves the physical removal of atoms or molecules from the surface of a source material

and the subsequent deposition of a solid material onto a substrate.

3.2.2 CHEMICAL METHOD

Chemical vapour deposition is a chemical process used to produce high-purity,

high-performance solid materials. The process is often used in the semiconductor industry

to produce thin films. In a typical chemical vapour deposition process, the wafer

(substrate) is exposed to one or more volatile precursors, which react and/or decompose

on the substrate surface to produce the desired deposit.

11
 3.2 THIN FILM DEPOSITION

3.3 ANTI-REFLECTION COATING

Though there are different types of deposition technique discussed above, the most

preferable techniques to give high performance on coating are detailed in below section.

The most preferable techniques are Dip coating method, Spin coating method and RF

Sputtering method. Each preferable technique has its own merits and demerits.

Important aspects of film deposition techniques are listed below. They are,

● The suitability for given coating materials.

● The precision of the layer thickness values.

● The optical quality of the deposited layers.

● The ability of the coatings to withstand high optical intensities.

12
 ● The uniformity of layer thickness values over a larger area.

● The consistency and stability of obtained refractive indices.

● The required substrate temperature.

● The time required for the growth.

3.3.1 DIP COATING METHOD

Dip coating technique can be described as a process where the substrate to be

coated is immersed in a solution and then withdrawn with a well-defined withdrawal

speed under controlled temperature and atmospheric conditions. The coating thickness is

mainly defined by the withdrawal speed, by the solid content and the viscosity of the

solution. If the withdrawal speed is chosen such that the sheer rates keep the system in the

Newtonian rule, the coating thickness can be calculated by the Landau-Levich equation.

The interesting part of dip coating processes is that by choosing an appropriate viscosity,

the coating thickness can be varied with high precision from 20 nm up to 50 μm while

maintaining high optical quality.

The atmosphere controls the evaporation of the solvent and the subsequent

destabilization of the sol by solvent evaporation, leads to a gelation process. Gelation is

the formation of a gel from a system with branched polymers. Branched polymers can

form links between the chains, which lead to progressively larger polymers. As the linking

continues, larger branched polymers are obtained and at a certain extent of the reaction

links between the polymer result in the formation of a single macroscopic molecule.and

13
the formation of a film due to the small particle size in the sol. The schematic diagram of

Dip coating Method is shown in below figure.

3.3.1 DIP COATING METHOD

3.3.2 SPIN COATING METHOD

Spin coating is a fast and easy method to generate thin and homogeneous organic

films using solutions. This method was first described by Meyerhofer using several

simplifications. The four distinct stages of the spin coating process are

● Deposition of the coating fluid onto the wafer or substrate

● Acceleration of the substrate up to its final, desired, rotation speed

● Spinning of the substrate at a constant rate; fluid viscous forces dominate the fluid

thinning behaviour

● Spinning of the substrate at a constant rate, solvent evaporation dominates the

coating thinning behaviour

14
 The spin coating method is simple, inexpensive, non-vacuum and low temperature

technique for synthesizing thin films. Spin coating method offers many advantages for the

fabrication of coatings, including excellent control of the stoichiometry of precursor

solutions, ease of compositional modifications, customizable microstructure, ease of

introducing various functional groups or encapsulating sensing elements, repeatability of

coatings, single side coating, relatively low annealing temperatures, the possibility

deposition on small area substrates and simple and inexpensive equipment.

Spin coating method is more suitable to prepare materials because it permits

molecular-level mixing and processing of the raw materials and precursors at relatively

lower temperature and produces nano-structured bulk particles, powders and thin films.

The schematic diagram of Spin coating Method is shown in below figure.

3.3.2 SPIN COATING METHOD

15
3.3.3 RF SPUTTERUNG METHOD

RF Sputtering runs an energetic wave through an inert gas in a vacuum chamber

which becomes ionized. The target material or cathode which is to become the thin film

coating is bombarded by these high energy ions sputtering off atoms as a fine spray

covering the substrate to be coated. RF Magnetron sputtering uses magnets behind the

negative cathode to trap electrons over the negatively charged target material so they are

not free to bombard the substrate, allowing for faster deposition rates.

Over time, positive ions are produced which accumulate on the surface of the target

face giving it a positive charge. At a certain point this charge can build up and lead to a

complete secession of sputtering atoms being discharged for coating.

By alternating the electrical potential with RF Sputtering, the surface of the target material

can be “cleaned” of a charge build up with each cycle. On the positive cycle electrons are

attracted to the target material or cathode giving it a negative bias. On the negative portion

of the cycle - which is occurring at the radio frequency of 13.56 MHz used internationally

for RF power supply equipment - ion bombardment of the target to be sputtered continues.

RF Sputtering offers several advantages depending upon your specific application.

RF plasmas tend to defuse throughout the entire chamber rather than concentrating around

the cathode or target material as with DC Sputtering.

RF Sputtering can sustain plasma throughout the chamber at a lower pressure (1-15

mTorr). The result is fewer ionized gas collisions equalling more efficient line-of-site

deposition of the coating material.

16
 Because with RF Sputtering the target material is being “cleaned” with each cycle

from building up a charge it helps reduce arcing. Arcing is where there is an intensely

focused and localized discharge emanates from the target material or cathode into the

plasma that creating droplets and problems with non-uniform film deposition. RF

Sputtering greatly reduces the build-up of a charge in a specific location on the surface of

the target material that leads to the sparks that creates the arc which causes numerous

quality control issues.

RF Sputtering also reduces the creation of “Race track erosion” on the surface of

the target material. With Magnetron Sputtering, a circular pattern becomes etched into the

surface of the target material as a result of the circular magnetic field of the magnetron

focusing the charged plasma particles close to the surface of the sputter target. The

diameter of the circular pattern is the result of the magnetic field.

With RF Sputtering the width and depth of the race track is much less due to the

AC nature of the RF discharge with electrons less confined by the magnetic field. The

plasma spreads out more producing a larger, wider and shallower racetrack. This makes

for better, more uniform and efficient utilization of target coating materials without the

deep etching of “Race track erosion”.

Another advantage of RF Sputtering is that there is no disappearing anode effect

when the substrate to be coated becomes insulated and acquires a charge as with DC

Sputtering. All surfaces develop a charge in plasma as a result of electrons moving much

faster than ions due to their smaller size and kinetic energy.

17
 However, as a result of the AC modulation of the power at radio frequencies, the

material to be coated with RF Sputtering does not acquire as great a charge build up due

to it being discharged each half cycle and becoming insulated - which over time can

eventually lead to a cessation of the thin film deposition. With RF Magnetron Sputtering

the magnetic field forms a boundary "tunnel" which traps electrons near the surface of the

target improving the efficiency of gas ion formation and constraining the discharge of the

plasma. In this way, RF Magnetron Sputtering allows for higher current at lower gas

pressure that achieves an even higher deposition rate. The schematic diagram of RF

sputtering process method is shown in below figure.

3.3.3 RF SPUTTERING METHOD

18
 CHAPTER – 4

RESULT AND DISCUSSION

19
4.1 Material Morphology:

The synthesized ZnO nano particles are characterized by Ultra violet spectra (UV)

and Scanning microscope (SEM) with EDAX. The SEM image of pure ZnO illustrates

that no surface gaps are fashioned though it's composed of interconnected spherical nano

particles with a mean grain size of ∼110 nm with slight activity.

The discovered SEM results indicate that ZnO nanoparticles haven't show any

result on the morphology. In the EDAX spectra of the ready samples, the fundamental

microanalysis of the anion-doped materials is summarized within the inserted table.

Energy Dispersive X-ray Analysis, EDAX, is an x-ray technique used to identify the

elemental composition of materials. The discovered EDAX spectra make sure the purity

of pure ZnO nano particles. Further, the EDAX spectra make sure the presence of

components, namely Zn, O2 and little quantity of carbon as shown in below figure.

The actinic radiation absorption spectra discovered for Zno is also shown. As

mentioned the absorption spectra of pure Zno nano particle show a peak precisely vary

within the range below four hundred that is solely beneath the actinic radiation region.

The discovered SEM result shows that the synthesized ZnO nano particle has

flower like structure and also the peaks within the SEM result confirms the crystalline

nature of the ZnO nano particle. The surface morphology of ZnO sample examined

through SEM image is shown in below figure.

20
4.1.1 SEM image of ZnO at 300nm 4.1.2 SEM image of ZnO at 200nm

4.1.3 SEM and EDAX image of ZnO nano particle

21
4.2 BAND GAP CALCULATION

The Band gap of synthesised pure ZnO nano particles is calculated with the help of

Ultra violet spectra graph with x-axis as Wavelength and y-axis as Absorbance is shown

below.

4.2 Ultraviolet spectra of ZnO

In the above graph, the peak of ZnO is below 400. The slope for the above peak

graph cuts the X-axis at ~440 nm. The slope for the absorbance and wavelength of ZnO is

440nm. The band gap (Eg) is calculated by using the equation given below.

Eg = hc/λ

Where,

h is planks constant

c is velocity of light in air

22
λ is wavelength

h= 6.626×10-34 Js

c= 3×108 m/s

λ= 440 nm

Eg = 6.626×10-34×3×108 / 440×10-9

Eg= 4.517×10-19 J

Where, 1 eV= 1.602×10-19J.

Therefore,

Eg= 2.818 eV.

The measured value of band gap energy for pure ZnO is calculated above. This in

turn enhances the performance of solar cells as well as increases the absorbance of visible

light .A decrease in the band gap value is noticed (i.e., 2.8 eV) when the ZnO nanoparticle

is synthesized. As a result, the absorption of light in the visible region takes place.

23
4.3 EFFICIENCY GRAPH

In our current project, we used Dip coating method and RF sputtering method to

increase the light trapping capacity of the Solar cell. The efficiency graph of Dip coating

method and RF sputtering method is shown below.

4.3.1 DIP COATING GRAPH

In dip coating method the solar cell has been nano coated with zinc oxide to

increase the efficiency. This increases the ability of the nano coated solar cell to absorb

the sunlight by reducing the reflection of the sunlight. The below figure shows the

variation of voltage with respect to time by the solar cell between coated and non-coated

cell.

4.3.1 DIP COATING EFFICIENCY GRAPH

24
 We have plotted the graph between the voltage and time for the 5v commercial

solar cell of about 7 hours in the sunlight. The observed graph shows that there is an

increase in power output voltage of about 3.27%. There is the slight increase in the output

voltage, this is due to the second layer of dip coated ZnO nano particles. As the band gap

of the synthesized ZnO (2.8 eV) which is slightly lower than the bulk sized ZnO (3.3 eV),

this layer reduces the reflection of the incident sunlight to a considerable amount and also

increases the absorption of sunlight.

4.3.2 RF SPUTTERING GRAPH

RF sputtering technique is a lot of appropriate to coat the synthesized ZnO nano

particles over the photovoltaic cell. Sputtering technique coats the ZnO with uniform

thickness than the dip coating method. Sputtering technique will be done solely on little

sized solar cells. Our 5V industrial photovoltaic cell is just too massive for this sputtering

technique, therefore we've done this experiment on the 2V industrial photovoltaic cell.

We have plotted the graph between the voltage and time for the 2v industrial solar

cell of about 7 hours in the sunlight. The observed graph shows that there is an increase in

power output voltage of about 22%. There is the massive increase in the output voltage,

this is due to the coated layer of RF sputtering ZnO nano particles. The below figure

shows the variation of voltage with respect to time by the solar cell between coated and

non-coated cell.

25
4.3.2 RF SPUTTERING EFFICIENCY GRAPH

DIP COATED SOLAR CELL NON COATED SOLAR CELL

4.3.3 SOLAR CELL

26
CHAPTER – 5

CONCLUSION

27
5.1 CONCLUSION

In this project we have coated the ZnO nano particles on the Solar cell by

Dip Coating method and RF Sputtering method. The structural and morphological

characteristics of the material were investigated through Scanning Electron Microscope

(SEM) and Ultra violet spectra. The coating over the solar cell increases the efficiency of

the solar cell of about 3.7% and 22% in Dip coating method and RF Sputtering method

respectively.

28
CHAPTER – 6

REFERENCES

29
6.1 REFERENCES

[1] Khaldun A. Salman (2012), Effective conversion efficiency enhancement of solar cell

using ZnO/PS antireflection coating layers, Solar Energy, Vol. 86, Issue 1, pp. 541-547.

[2] Han-Ki Kim, Kwun-Bum Chung, Jinha Kal (2019), Comparison of ZnO buffer layers

prepared by spin coating or RF magnetron sputtering for application in inverted organic

solar cells, Journal of Alloys and Compound, Vol. 778, pp. 487-495.

[3] Dong Hwan Wang , Jason Seifter , Jong Hyeok Park , Dae-Geun Choi , and Alan J.

Heeger (2012), Efficiency Increase in Flexible Bulk Hetero junction Solar Cells with a

Nano-Patterned Indium Zinc Oxide Anode, Advanced Energy Materials, Vol. 2, Issue 11,

pp. 1319-1322.

[4] J.Y. Chen, K.W. Sun (2010), Enhancement of the light conversion efficiency of silicon

solar cells by using nano imprint anti-reflection layer, Solar Energy Materials and Solar

cells, Vol. 94, Issue 3, pp. 629-633.

[5] Dinguo Chen (2001), Anti-reflection (AR) coatings made by sol-gel processes: A

review, Solar Energy Materials and Solar Cells, Vol. 68, Issue 3-4, pp. 313-336.

30
[6] Kang-Soo Han, Hyunju Lee, Donghwan Kim, Heon Lee (2009), Fabrication of anti-

reflection structure on protective layer of solar cells by hot-embossing method, Solar

Energy Materials and Solar Cells, Vol. 93, Issue 8, pp. 1214-1217.

[7] Wisam J. Aziz, Asmiet Ramizy, K. Ibrahim, Z. Hassan, Khalid Omar (2011), The

effect of anti-reflection coating of porous silicon on solar cells efficiency, Optik

International Journal for Light and Electron Optics, Vol. 122, Issue 16, pp. 1462-1465.

[8] Azmira Jannat, Woojin Lee, M. Shaheer Akhtar, Zhen Yu Li , O.-Bong Yang (2016),

Low cost sol–gel derived SiC–SiO2 nano composite as anti-reflection layer for enhanced

performance of crystalline silicon solar cells, Applied Surface Science, Vol. 369, pp. 545-

551.

[9] Y.F. Makableh , R. Vasan, J.C. Sarker, A.I. Nusir, S. Seal, M.O. Manasreh (2014),

Enhancement of GaAs solar cell performance by using a ZnO sol–gel anti-reflection

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