Get Familiar with Dye Sensitized Solar Cells -

Muhammad Farhan Sabir
PhD-EE-05F20

CONTENTS
1. INTRODUCTION TO DYE SENSITIZED SOLAR CELLS
2. MATERIALS USED FOR FABRICATION OF DYE SENSITIZED SOLAR
CELLS
3. WORKING PRINCIPLE/MECHANISM OF DYE SENSITIZED SOLAR
CELL
4. LAYERED STRUCTURE OF DYE SENSITIZED SOLAR CELLS
5. ENERGY BAND GAP DISTRIBUTION
6. DIAGRAM OF DYE SENSITIZED SOLAR CELL
7. BASIC CIRCUIT DIAGRAM OF DYE SENSITIZED SOLAR CELLS
8. I-V CURVE DIAGRAM FOR DYE SENSITIZED SOLAR CELL
9. SYNTHESIS TECHNIQUES USED FOR THE MANUFACTURE OF DYE
SENSITIZED SOLAR CELL
10. CHARACTERIZATION TECHNIQUES USED TO EVALUATE THE
PERFORMANCE AND MATERIAL COMPOSITION OF DYE
SENSITIZED SOLAR CELLS
11. ADVANTAGES AND DISADVANTAGES OF DYE SENSITIZED SOLAR
CELLS
2
26-08-2021
Muhammad Farhan Sabir - mfarhansabir@hotmail.com

INTRODUCTION
Michael Grätzel and Brian O’Regan invented
“Dye-sensitized solar cells” (DSSC), also
called “Grätzel cells”, or ‘GCells’ in 1991.
DSSCs are a third generation photovoltaic
(solar) cell that converts any visible light into
electrical energy.
Response of DSSC is similar to that of the
human eye, infrared and ultraviolet have little
effect to its energy harvesting capabilities.
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INTRODUCTION
DSSC is a disruptive technology –
Converts both Artificial & Natural
Light to Energy.
It mimics nature’s absorption of
light energy – Artificial
Photosynthesis
Can be used to make thin and
light-weight flexible solar
modules
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▪ A DSSC is a thin-layer solar
cell formed by sandwich
arrangements of two
transparent conducting oxides
(TCO) electrodes.
▪ Main Electrode – mesoporous
TiO2 layer coated with a
photosensitizer.
▪ Counter Electrode - finely
divided Pt deposited on TCO
▪ Inter-layer space - organic
electrolyte with redox
mediator
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▪Semiconductor
oxides
▪ ZnO, SnO2, Nb2O5, In2O3
▪TiO2 (anatase)
▪ High porosity (60%)
▪ High stability
▪ Wide band gap energy
3.2 eV ( 388 nm)
SEMICONDUCTOR
7
S. Mori, S. Yamigada, “TiO2-based Dye-Sensitized Solar Cell” in Nanostructure Materials
for Solar Energy Conversion, T. Soga (Ed.), 2006, Elsevier.
M. Grätzel. Acc. Chem. Res. 2009, 42, 1788 - 1798.
SEM
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▪ Nanostructured Photoelectrode:
▪ The use of sensitized wide bandgap semiconductors such as TiO2, or ZnO resulted in high chemical
stability of the cell due to their resistance to photocorrosion.
▪ ZnO possesses a band gap of 3.37 eV and a large excitation binding energy of 60 meV.
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Fig. Schematic illustration of the effects of annealing temperature on the charge-collection
and light-harvesting properties of TiO2 nanotube-based dye-sensitized solar cells.

ε (mmol/cm2)
l (nm)
0
5000
10000
15000
400 600 800 1000
9
Sensitizer Dye
D. L. Officer et al. J. Phys. Chem. C, 2007, 111, 11760–11762.
H. Sugihara et al. Sol. Energy Mat. Sol. Cells 2010, 94, 297 – 302.
N N
N
N
Zn
HOOC
COOH
Ru
N
N NCS
NCS
N
N
HO2C
COO NBu4
COO
HO2C
NBu4
Ru
N
SCN NCS
N
NCS
N CO2H
HO2C
CO2H
(in DMF)
(in EtOH)
(in EtOH)
Suitable dyes absorb strongly
in the visible region.
Zinc Porphyrin Dye
N719 Dye
The
Role
Of
A
Sensitizer
In
DSSC
Is
As
A
Molecular
Electron
Pump.
Black Dye
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10
Sensitizer Dye
Suitable dyes chemisorb to the semiconductor.
E.g. One molecule of N719 exhibiting bidentate binding to TiO2.
surface
Y. Narita et al. Electrochem. Solid-State Lett. 2009, 12, B167 – B170.
Ti
OH
Ti
OH
TiO2
surface
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Semiconductor
Dye
Dye +
3 I-
I3
-
Counter
electrode
External Circuit
Electron
transfer
11
B. C. O’Regan, J. R. Durrant, Acc. Chem. Res. 2009, 42, 1799 – 1808.
h
Redox Couple/Electrolyte
Iodide/Triiodide
I3
- + 2e- → 3I-
Electron
transfer
Electron
transfer
Electron flow
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12
✓ E.g. Platinum loaded on
Fluorine-doped SnO2 (FTO)
– a transparent conducting
oxide (TCO)
✓ Pt is an excellent catalyst for
triiodide reduction
x Rare and expensive
x Incompatible with some
electrolytes e.g. poly sulfide
Counter Electrode
FTO
Pt
I3
-
3I-
To
external
circuit
2 e-
G. Boschloo; A. Hagfeldt. Acc. Chem. Res. 2009, 42, 1819 – 1826.
I3
-/I-
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Fig. Materials Used for each Part of DSSC & Required Material Properties

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▪ HOMO
▪ “Highest Occupied Molecular Orbital“
▪ LUMO
▪ "Lowest Unoccupied Molecular Orbital“
▪ Smaller HOMO-LUMO gaps correspond to
better stability.
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1. The sensitizer adsorbed on to the TiO2 surface absorbs
a photon to produce an excited state, which efficiently
transfers one electron to the TiO2 conduction band.
2. The oxidized dye is subsequently reduced by electron
donation from an electrolyte containing the
iodide/triiodide redox system.
3. The injected electron flows through the semiconductor
network to arrive at the back contact then through the
external load to the counter electrode, which is made of
platinum sputtered conducting glass.
4. The circuit is completed by the reduction of triiodide at
the counter electrode, which regenerates iodide.

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1
2
3
5
4

▪ Dark current-voltage characteristics of
the mesoscopic TiO 2 electrodes
shown in Fig. in sandwich cells, with
and without adsorbed ruthenium dye.
▪ The counter electrode was Pt-coated
FTO.
21
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• Incident radiation
100 mW/cm2
• TiO2 semiconductor
• Dye sensitizer
• I- /I3
- in ionic liquid
electrolyte
22
L. Han. et al. J. Jpn. Appl. Phys. 2006, 45, L638 – L640.
JSC 20.9 mA/cm2
VOC 0.736 V
Ru
N
SCN NCS
N
NCS
N CO2H
HO2C
CO2H
J-V and Power curves
Most Efficient DSSC (Efficiency 11.1%)
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Fig. Steps of fabrication

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Fig. Steps of fabrication

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Pazoki, M et al. (2017). “Characterization Techniques For Dye-sensitized Solar Cells”. Energy &
Environmental Science, 10(3), 672–709.

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• Absorption spectra : 390-700 nm.
• Peak absorbance : 500-550 nm.
• DSSC works in a wide range of indoor lighting conditions.
• Has no dramatic efficiency changes according to the light angle

▪ Dye-sensitized solar cells absorb
>85% of visible light,
▪ But almost no light in the near-
infrared.
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▪ Aesthetic Advantages:
▪ Dyes determine the color of the device.
▪ Can be transparent
▪ Can be flexible
▪ Easy to make
▪ .
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▪ Vlachopoulos, Nick, et al. "New approaches in component design for dye-sensitized solar cells."
Sustainable Energy & Fuels 5.2 (2021): 367-383.
▪ Kalyanasundaram, Kuppuswamy. Dye-sensitized solar cells. CRC press, 2010.
▪ Sharma, Khushboo,Vinay Sharma, and S. S. Sharma. "Dye-sensitized solar cells: fundamentals and current
status." Nanoscale research letters 13.1 (2018): 1-46.
▪ Mariotti, Nicole, et al. "Recent advances in eco-friendly and cost-effective materials towards sustainable
dye-sensitized solar cells." Green Chemistry 22.21 (2020): 7168-7218.
▪ Koide, Naoki, and Liyuan Han. "Measuring methods of cell performance of dye-sensitized solar cells."
Review of scientific instruments 75.9 (2004): 2828-2831.
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