Experimental investigation of dye-sensitized solar cell with anthocyanin and xanthene dyes

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:

Operation, materials and methods", Renewable and

Sustainable Energy Reviews 51, 1306­1325.

[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",

Materials Science and Engineering B 162, 32­39.

[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

dyes in water purification: Anthocyanin as TiO

2

-

sensitizer in methyl orange photo-degradation", Solid

State Sciences 13, 1268-1275.

[9]

Okoli L, U., Ozuomba,j, and Ekpunobi. (2013),

"Influence of Local Dye on the Optical band-gap of

Titanium Dioxide and its performance as a DSSC

Material", Research Journal of Physical Sciences Vol.

1(10), 2320­4796.

Beant College of Engineering and Technology,

Gurdaspur, Punjab 143521(India)

Frequently asked questions

What are solar cells and how are they categorized?

Solar cells are devices that convert solar radiation into electrical energy. They are divided into three generations based on their performance:

• First Generation: High efficiency but costly due to silicon material.
• Second Generation: Lower performance but low fabrication cost using thin films.
• Third Generation: Hybrid cells like dye-sensitized solar cells (DSSCs), not limited by the Shockley Queisser Limit (SQL).

What is a Dye-Sensitized Solar Cell (DSSC) and how does it work?

A Dye-Sensitized Solar Cell (DSSC) belongs to the third generation of solar cells. It transforms light energy into electricity by sensitizing larger band gap semiconductor materials like TiO₂ and ZnO₂. The conversion depends on a dye that absorbs light, excites electrons, and injects them into the conduction band of the semiconductor.

What are the components of a DSSC and their roles?

The key components of a DSSC include:

• Conductive Oxide Glass: (FTO or ITO) serves as the substrate.
• Wide Band Gap Metal Oxide Layer: (TiO₂) acts as an electron injector.
• Sensitizer (Dye): Absorbs light energy.
• Electrolyte Solution: Provides electrons and completes the circuit.
• Counter Electrode: Glass coated with platinum and carbon.

What is the operating principle of a DSSC?

The dye absorbs light energy, exciting electrons from the ground state to the excited state, then injecting these electrons into the conduction band of the wide band gap material. The oxidized dye receives an electron from the electrolyte solution, and the process repeats.

What is the experimental procedure for creating a DSSC?

The experimental procedure involves:

• Conductive Glass Preparation: Selecting and cleaning FTO glass.
• Electrode Preparation: Applying TiO₂ paste onto the conductive glass using the doctor blade method and annealing it.
• Dye Preparation: Isolating anthocyanins from natural plants or preparing xanthene dyes.
• Counter Electrode Preparation: Applying carbon paste onto conductive glass using the doctor blade method and annealing it.
• Electrolyte Solution Preparation: Mixing potassium iodide and iodine in ethylene glycol.
• Assembly: Binding the TiO₂ electrode and counter electrode together with binder clips and adding electrolyte solution.

How is the efficiency of a DSSC calculated?

The solar conversion efficiency (η) of a DSSC is estimated using the formula: η = P_max / P_in, where P_max is the maximum output power and P_in is the input power. The fill factor (FF) is determined as: FF = I_max * V_max / I_sc * V_oc, where V_oc is the open-circuit voltage and I_sc is the short-circuit current.

What were the optical results of the dyes used in the experiment?

The optical results from UV-VIS spectroscopy showed that titanium dioxide absorbed light in the ultraviolet region. Eosin yellow had maximum absorption in the visible zone at 500 nm, while promengrate juice had maximum absorption in the UV and visible zones at 200 nm and 400 nm.

What were the electrical conversion efficiencies of the solar cells made from eosin yellow and promengrate juice?

The electrical conversion efficiencies of the solar cells made from eosin yellow and promengrate seeds were calculated as 1.48% and 0.10% respectively.

What are the benefits of using natural dyes in DSSCs?

Natural dyes are easily available, easy to prepare, environmentally friendly, and can improve light absorption when combined with materials like titanium dioxide. They contain carbonyl (C) and hydroxyl (OH) groups that bond to the TiO₂ surface, facilitating electron transfer.

What is the acknowledgement for this study?

The authors express special thanks to the Head Department of Mechanical Engineering of Beant College of Engineering and Technology Gurdaspur for providing facilities for research work in their solar energy laboratories and to the faculty members for their help and valuable suggestions.

Details

• College: Beant College of Engineering and Technology (Engineering)
• Course: M.Tech (Thermal Engineering
• Grade: A
• Authors: Amninder Singh (Author), Brij Bhushan (Author), Nrip Jit (Author), Sandeep Gandotra (Author)
• Publication Year: 2016
• Pages: 6
• Catalog Number: V336152
• ISBN (eBook): 9783668272699
• ISBN (Book): 9783668272705
• Language: English
• Tags: experimental