Dye-sensitized solar cells are fabricated from xanthene (eosin yellow) and anthocyanin (pomegranate seeds) dyes. TiO2 films as an electron transfer material on Fluorine doped tin oxide glass layers were prepared by doctor blading method. Carbon coated counter electrode material used as an electron injector material and liquid Iodide/Iodine electrolyte solution was used to inject the extra electrons in the cell and to complete the electrical circuit in the solar cell.
Eosin Yellow and pomegranate dyes used to increase the absorption of the TiO2. The electrical conversion efficiencies of solar cells determined with eosin yellow and pomegranate seeds were calculated as 1.48% and 0.10% respectively, on a sunny day in Beant College of Engineering and Technology, Gurdaspur.
1. Introduction
Solar cells are the devices which converts solar
radiation into electrical energy. These are divided into
three generations according to their performance.
These are first, second, the third generation of solar
cells in which the first generation has a greater
efficiency with a limitation of increased cost
production. These cells are made from silicon material
having p and n-type semiconductor material. Second
generation solar cells made by developing thin films
have a less overall performance, but the fabrication
technique and cost is very low according to other
technologies. Fabrication of solar cell with thin film
methods reduces the thickness from millimeter to just
microns. The main limitations of the first and second
generation solar cell are that their working limited by
the Shockley Queisser theoretical limit of ~30% for a
single p-type and n-type semiconductor junction
[1].The third generation solar cells not from the
category of first and second generation of solar cell
these are a hybrid type of solar cells such as dye
sensitized solar cells. Different methods and
Techniques are used for the fabrication of third
generation solar cells and are not affected by the
Shockley Queisser limit (SQL). Hybrid type of solar
systems or cells are taken into 3
rd
generation
technology, which is not much commercially utilized
and has a promising future in present research.
A dye-
sensitized solar cell belongs to the third generation of
solar cell which transforms the light energy into
electricity, by sensitization of larger band gap
semiconductor materials such as TiO
2
and ZnO
2.
The
conversion of solar energy into electricity of the solar
cell cells depends on a dye. Gratzel and coworkers [2]
started their working on the dye-sensitized solar cell
and attracted much attraction. The dye-sensitized solar
cells have wide band gap based on semiconductor
material film made on conductive glass. The
absorbance of the semiconductor material is increased
by dye molecules which absorb the light energy. Light
energy absorbs by dye excites the electrons of the dye
from the ground state to excited state and transfer the
electrons from the excited state into the conduction
band of the wide band gap semiconductor material.
The transferred electrons pass through the wide band
gap material film to the load as shown in the figure and
the hole created in the dye is filled by an electron
donated by the electrolyte solution. Then electrolyte
solution filled up the hole with the electron coming
from the load after losing his energy through counter
electrode, again and again, this process is repeated to
complete the circuit of the solar cell. The absorbance
of a metal oxide material such as titanium dioxide is
increased by using natural and chemical pigments such
as anthocyanin and xanthene. The anthocyanin and
xanthene belong to the group of natural and chemical
dyes responsible for several colors present in
vegetables fruits and flowers [3]. Carbonyl (C) and
hydroxyl (OH) groups present in the anthocyanin
molecule make a bond to the surface of a TiO
2
structure. This makes electron transfer from the
anthocyanin molecule to the Conduction band of TiO
2
.
Anthocyanin from various plants gave different
Sensitizing performances. The availability of natural
dyes are easy, and they are easy to prepare and fully
environmental friendly [4]. Anthocyanins pigment
from fruits, vegetables, and flowers make bond with
the TiO
2
surface and transfer the electrons into the
conduction band. The principal of photophysical for
dye-sensitized solar cell are listed below as:
D + h D*
(1)
Where `D' represented as a dye, `hv' is photon energy
from sunlight and D* is oxidized state of dye [4]. Once
an electron gets injected into the conduction band of
the wide band gap semiconductor TiO
2
film, the dye
molecule (photosensitizer) become oxidized, above
equation become as below:
D* +TiO
2
D+ e
-
(TiO
2
)
(2)
Fig.1: Dye sensitized solar cell DSSC diagram.
The injected electron is transported between the TiO
2
material and then gets extracted to a load where the
work done delivered as an electric energy as:
e
-
(TiO
2
) + Electrode TiO
2
+ e
-
(Electrode) + Energy (3)
Electron between the TiO
2
photoelectrode and the
carbon coated counter electrode electrolyte containing
iodide and iodine redox ions is used to fill the cell.
There is no permanent chemical change or
transformation while the generation of electric power
in the dye-sensitized solar cell.
2. Operating principle
Dye-sensitized solar cell works on the conversion of
light energy into output electrical energy as shown in
the fig.1 above and Following steps are included in the
operating principle [5]:
1. Conducting oxide glass (fluorine-doped tin
oxide (FTO) or indium doped tin oxide (ITO))
on which the solar cell is made.
2. Wide band gap metal oxide layer (electron
injector usually made from TiO
2)
.
3. Sensitizer or dye molecules, which absorb the
light energy.
4. An electrolyte solution which increases the
electrons and completes the circuit.
5. A counter electrode, glass coated with
platinum and carbon.
In the dye-sensitized solar cell, the dye absorbs the
light energy and the electrons of the dye get excited
from the ground state to excited state and injected the
electrons into the conduction band of the wide band
gap material. The hole created on the dye molecules
get oxidized [6]. These injected electrons pass through
the metal oxide TiO
2
layer to the load towards counter
electrode to complete the circuit. The oxidized dye
receives an electron from electrolyte solution and the
iodide (I
-
) molecules are oxidized to triiodide ions (I
3
-
)
[7]. Finally, and migration of electron through the
external load completes the circuit [8].
3. Experimental procedure
3.1 Conductive glass
Take a piece of FTO glass (2 cm × 2 cm), which is a
piece of glass coated with a transparent and conductive
material, fluorine-doped tin oxide (FTO) on one side.
Determine the conducting side using a multimeter. To
do this, set the multimeter to resistance mode, plug the
two leads into the multimeter, and measure the sheet
resistance on the two sides using the probes (13). The
conducting side will give low resistance (tens of ohms)
while the uncoated side will not give any value. Notice
that the FTO side has more over it.
3.2
Electrode
Electrode is prepared by taking 3.5 gram of TiO
2
(Anatase) powder in 15 ml of ethanol in a mortar
pestle. Grind the mixture until a uniform lump-free
paste is produced. Adhesive tape is used to cover the
area 1x1 cm
2
of the Fluorine doped glass plate, and
TiO
2
solution uniformly spread over the surface by
glass rod and thickness of the solution is controlled by
doctor blade method as shown in the figure below:
Fig.2: TiO
2
film formation on the conductive glass by
doctor blade method.
Fig.3: SEM image of TiO
2
on the conductive glass.
Above figure shows the 3-4 micrometer thickness of
the TiO
2
on the conductive glass as shown in the
figure. The TiO
2
film is dry in air. After two minutes,
the adhesive tape is removed, and the glass is annealed
at 300
0
C for one hour on a hot plate and then cooled it
to room temperature.
3.3
Dye preparation
The anthocyanins pigments are isolated from natural
plants (promengrate seeds) 10 g of seeds were crushed
in 50 ml solution of ethanol, and filtered with filter
paper. The following procedure makes xanthene dyes:
1 gr of xanthene dyes (eosin yellow) mix with 5 ml of
ethanol properly. The solution obtained are stored in a
bottle. Dip the TiO
2
electrode in the dye for two hours.
3.4 Counter electrode
Same doctor blade technique has prepared a counter
electrode. Carbon power is collected with the help of
candle soot on the aluminium foil. Then carbon power
is mixed with small amount of acetic acid after mixing
it with the acidic solution carbon paste is then apply on
the fluorine-doped tin oxide glass by doctor blade
method as shown in the figure as:
Fig.4: Carbon film formation on the conductive glass
by doctor blade method.
Then dry the film in air. After removing the tape and
the film is annealed at 300
0
C for 2-3 minutes.
3.4
Preparation of electrolyte solution
0.5M potassium iodide (0.83gm) and 0.05M iodine
(0.127gm) are mixed in 10 ml of ethylene glycol to
make electrolyte solution. One or two drops of the
electrolyte solution are used between the electrode and
the counter electrode to fill the extra electrons in the
solar cell. Binder clips are to hold the electrode and
counter electrode together.
3.5
Assemble and determine output
characteristics of solar cell
After making the both electrodes then TiO
2
electrode is
carefully bound together with the carbon coated
counter electrode with the help of two binder clips.
Always keep the TiO
2
electrode towards face up
direction so that light falls on it. Then add one- two
drops of the electrolyte solution placed on the edges of
the conductive glasses to make electrical contacts
between two electrodes. Both the positive and negative
terminals of the solar cell attached with the alligator
clips carefully. Then connect the alligator clips with
multimeter terminals to check the current and voltage.
Binder clips are used to hold the glasses together.
Fig.5: Schematic representation of a Dye-sensitized
solar cell with TiO
2
and carbon coated the counter
electrode.
3.6 Data reduction
The solar conversion efficiency () of a dye-sensitized
solar cell [3] can be estimated using the conversion
efficiency formula:
= Pmax / Pin
(4)
Where Pmax, and Pin is the maximum output and input
power. The fill factor (FF) of a dye-sensitized solar can
be determined as:
FF = Imax * Vmax / Isc * Voc
(5)
Where Voc is the open-circuit voltage and Isc is the
short-circuit current. Imax is the maximum current and
Vmax is the maximum voltage. The solar conversion
efficiency of a dye sensitized solar cell can be
calculated by:
= Isc * Voc * FF / Pin
(6)
4. Results and Discussions
4.1 Optical results of dyes
The optical results were made using UV-VIS
spectroscopy for dyes (eosin yellow and promengrate
seeds). The absorption of light in both the regions
visible and UV region of different samples are as given
below:
4.1.1 Titanium dioxide:
The optical measurement of titanium dioxide as shown
in the figure shows that absorption of light in the
visible region is almost negligible whereas it show
some absorption in the ultraviolet region as shown as:
Fig.6: UV-vis spectroscopy of titanium dioxide (anatase)
TiO
2
material.
4.1.2 Eosin Yellow
Optical results for eosin yellow in the visible region
shown in the below graph. The graph shows the
maximum absorption in the visible zone at the 500 nm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
200
400
600
800
Ab
so
rb
an
ce
(a
.u
)
Wavelength (nm)
wavelength with absorbance value 1.59 a.u, as shown
in Figure.
Fig.7: UV-vis spectroscopy of titanium dioxide with
eosin yellow dye.
4.1.3 Promengrate seeds
Optical results for promengrate juice in the visible
region shown in the below graph. Graph shows the
maximum absorption in the UV and visible zone at the
wavelength 200 nm and 400 nm with the absorbance
value of 1.38 a.u and 0.59 a.u given as:
Fig.8: UV-vis spectroscopy of titanium dioxide with
promengrate juice dye.
The above graphs shows the combination of titanium
dioxide metal oxide material with dyes. This
combination absorbs some amount of light in the
visible region as shown in the figure. The carbonyl and
hydroxyl groups present in the anthocyanin and
xanthene pigment makes bonds with the wide band gap
semiconductor material (TiO
2
) which is then
responsible for the absorbance of incident photons. The
output results such as an electrical conversion
efficiency (), an open circuit voltage (Voc), a short
circuit current (Isc) and a fill factor (FF) have been
calculated as
Fig.9: Currentvoltage results of the cell determined
from eosin yellow.
Fig.10: Currentvoltage results of the cell determined
from the promengrate juice.
As the above graph shows the Currentvoltage results
of the cell determined from eosin yellow and
promengrate juice. Currentvoltage results of cell
determined from eosin yellow and promengrate juice
shows the maximum voltage, current at 0.450 V/cm
2
,
3.35 mA/cm
2
and 0.190 V/cm
2
, 0.62 mA/cm
2
and short
circuit current, open circuit voltage at 3.95 mA/cm
2
,
0.557 V/cm
2
and 0.77 mA/cm
2
,0.230 mV/cm
2
.
.
Table.1: The electrical conversion efficiency of the
solar cell that are made from eosin yellow and
promengrate juice as shown in the table as:
S no.
DYE
ISC
Voc FF
Pin
()
1.
EOSIN
YELLOW
3.95
0.55
7
0.6
8
100.
5
1.4
8
2.
PROMEG
RANATE
SEEDS
0.77
0.23
0
0.6
6
116.
5
0.1
0
As shown in the above Table 1, The electrical
conversion efficiency of the solar cell that is made
from eosin yellow is higher than that of the cell
fabricated from the promengrate juice. The reasons for
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
200
300
400
500
600
700
800
Ab
so
rr
ba
nc
e
(a
.u
)
Wavelength (nm)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0
200
400
600
Cu
rre
nt
(m
A
/cm
2)
Voltage (mV/cm2)
this might be the more absorption of light in the cell as
compared to that of promengrate juice shown in the
UV-vis spectroscopy of eosin yellow and promengrate
juice. The electrical efficiency of the solar cell from
eosin yellow and promengrate juice dye was
determined 1.48% and 0.11%.
5. Conclusion
Different ratios and compositions of the anthocyanin
pigment in various plants, vegetables, fruits, etc. show
the different color appearance. The natural plant dyes
that contain a high concentration of anthocyanins (such
as Raspberries, Pomegranate Juice, Cherries, Red
cabbage, Strawberry, black carrot, Skin of eggplant)
shows the greater absorption of visible light. The dye-
sensitized solar cell has been made using Doctor Blade
technique which is very easy as compared to others in
preparing thin film components, in the order (FTO /
TiO
2
/ D* / Electrolyte/carbon layer / FTO) and their
performances for different types of natural dyes and
chemical dyes. The electrical conversion efficiencies of
solar cells determined from eosin yellow and
promengrate seeds were calculated as 1.48% and
0.10% respectively, on a sunny day in Beant College of
Engineering and Technology, Gurdaspur.
Acknowledgement
The authors would like to express special thanks to the
Head Department of Mechanical Engineering of Beant
College of Engineering and Technology Gurdaspur for
providing the facilities for research work in their solar
energy laboratories. The authors would also like to
express special thanks to the faculty members for
providing the help and their valuable suggestions from
time to time.
References
[1]
Shockley, W., and Queisser, H. (1961), "Detailed
Balance Limit of Efficiency of p-n Junction Solar Cells",
Journal of Applied Physics 32, 510-519.
[2]
B,Regan and Grätzel, M. (1991), "A low-cost, high-
efficiency solar-cell based on dye sensitized colloidal
TiO
2
films", Nature 353, 73740.
[3]
Alhamed, M., Ahmad, S. and Wael. (2012), "Studing of
natural dyes properties as photo-sensitizer for dye
sensitized solar cell", Journal of Electron Devices 16,
1370-1383.
[4]
Calogero, G. and Marco, G. (2008), "Red Sicilian
orange and purple eggplant fruits as natural sensitizers
for dye-sensitized solar cells", Solar Energy Materials &
Solar Cells 92, 1341 1346.
[5]
Shalini, S., Balasundara, R., Prasanna, S., Mallick, K.
(2015), "Review on natural dye sensitized solar cells:
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[6]
Sharmaa, G., Balrajua, P., Kumar, M. and Roy, M.
(2009), "Quasi solid state dye sensitized solar cells
employing a polymer electrolyte and xanthene dyes",
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[7]
Oviri, K. and Ekpunobi, A. (2013), "Transmittance and
Band Gap Analysis of Dye Sensitized Solar Cell",
Research Journal of Recent Sciences ISSN, 2277-2502.
[8]
Zyoud, A., Zaatar, N., Saadeddin, I., Campet, G., Hakim,
M., Park, D. and Hikmat, S. (2011), "Alternative natural
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[9]
Okoli L, U., Ozuomba,j, and Ekpunobi. (2013),
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Material", Research Journal of Physical Sciences Vol.
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Beant College of Engineering and Technology,
Gurdaspur, Punjab 143521(India)
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- Amninder Singh (Author), Brij Bhushan (Author), Nrip Jit (Author), Sandeep Gandotra (Author), 2016, Experimental investigation of dye-sensitized solar cell with anthocyanin and xanthene dyes, Munich, GRIN Verlag, https://www.grin.com/document/336152
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