Dye-Sensitized Solar Cells

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Dye-Sensitized Solar Cells

• Sonja A. Francis7th March 2012

2
Solar Irradiation
Solar irradiation is the amount of radiant energy
emitted by the sun per area and unit time for a
given wavelength of light.
Visible IR ?
M. Skompska. Synthetic Metals 2010, 160, 1-15.
3
Is Solar Energy Viable?
Photovoltaic potential GJ per 1kW capacity solar
cell
Potential amount of solar energy collected
annually in Alberta with a 1 kW capacity solar
cell system 3.96 5.04 GJ Residential
Electrical Energy Usage in Alberta (2009) gt
32,000,000 GJ Maximum solar system capacity
required 8,300,000 kW ? 8.3 MW
J. Bell, T. Weis, Greening the grid, Powering
Albertas future with renewable energy. 2009
http//pubs.pembina.org/reports/greeningthegrid-r
eport.pdf. Retrieved 18th March 2010.
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General Solar Cell Structure
h?
Negative Terminal
Positive Terminal
Cell structure
Load
Electron flow in external circuit
T. Markvart, L.Castañer. Principles of Solar
Cell Operation in Practical Handbook of
Photovoltaics Fundamentals and Applications,
2003, Elsevier, Oxford, UK.
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Types of Solar Cells

• Semiconductor solar cell
• E.g. Crystalline silicon
• Organic/Polymer solar cell
• E.g. Fullerene/Poly-(p-phenylvinylene)

• Thin film solar cell
• E.g. CdS/CdTe

V. Fthenakis. Renewable Sustainable Energy Rev.
2009, 13, 2746 - 2750. Y. Cao et al. Sol. Energy
Mat. Sol Cells 2010, 94, 114 - 127. M.A. Green,
K. Emery, Y. Hishikawa, W. Warta, Prog.
Photovolt. Res. Appl. 2009, 17, 320 - 326.
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Dye-Sensitized Solar Cells (DSSCs)

• Main components
• Semiconductor electrode
• Dye sensitizer
• Redox couple in an electrolyte
• Transparent counter electrode coated with a
  catalyst

 www.chemphys.lu.se/research/subjects/cells/ Retri
eved 16th March 2010
V. Fthenakis. Renewable Sustainable Energy Rev.
2009, 13, 2746 - 2750. Y. Cao et al. Sol. Energy
Mat. Sol Cells 2010, 94, 114 - 127.
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Semiconductor

• E.g. Semiconductor oxides
• ZnO, SnO2, Nb2O5, In2O3
• TiO2 (anatase)
• High porosity (60)
• High stability
• Wide band gap energy 3.2 eV (? 388 nm)

SEM
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.
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Sensitizer Dye
Suitable dyes absorb strongly in the visible
region.
(in DMF)
(in EtOH)
(in EtOH)
D. L. Officer et al. J. Phys. Chem. C, 2007, 111,
1176011762. H. Sugihara et al. Sol. Energy Mat.
Sol. Cells 2010, 94, 297 302.
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Sensitizer Dye
Suitable dyes chemisorb to the semiconductor. E.g.
One molecule of N719 exhibiting bidentate
binding to TiO2. surface
TiO2 surface
Y. Narita et al. Electrochem. Solid-State Lett.
2009, 12, B167 B170.
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Redox couple/Electrolyte
Iodide/Triiodide I3- 2e- ? 3I-
h?
3 I-
Dye
Counter electrode
Semiconductor
Electron transfer
Electron transfer
Electron transfer
Dye
I3-
Electron flow
External Circuit
B. C. ORegan, J. R. Durrant, Acc. Chem. Res.
2009, 42, 1799 1808.
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Counter Electrode

• E.g. Platinum loaded on Fluorine-doped SnO2
  (FTO) a transparent conducting oxide (TCO)
• Pt is an excellent catalyst for triiodide
  reduction
• Rare and expensive
• Incompatible with some electrolytes e.g. poly
  sulfide

To external circuit
I3-
2 e-
3I-
I3-/I-
FTO
Pt
G. Boschloo A. Hagfeldt. Acc. Chem. Res. 2009,
42, 1819 1826.
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Processes in the DSSC

1. Photo-excitation
2. Electron injection and dye-relaxation
3. Electron flow
4. Re-entry
5. Reduction of electrolyte
6. Dye regeneration (reduction)

D
?
?
?
?
h?
?
Ox
?
Red
D/D
Dye
Electrolyte
CE
Semiconductor
B. C. ORegan, J. R. Durrant, Acc. Chem. Res.
2009, 42, 1799 1808.
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Electron transfer in the DSSC
VOC open circuit voltage maximum voltage the
dye-sensitized solar cell can achieve.
ISC - short circuit current maximum current
achieved (no load).
LUMO
Conduction Band
Fermi Level
VOC
Potential/V
Redox Potential
Fermi Level
HOMO
Semiconductor Dye Molecule
Electrolyte Cathode
not drawn to scale
G. Boschloo A. Hagfeldt. Acc. Chem. Res. 2009,
42, 1819 1826.
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Electrical Losses in DSSCs
D

1. Dye relaxation
2. Recapture by oxidised electrolyte
3. Recapture by oxidised dye

?
?
?
Red Ox
D/D
Semiconductor
Dye
Electrolyte
Pt
A. J. Bard L. R. Faulkner. Photoelectrochemistry
and Electrogenerated Chemiluminescence in
Electrochemical Methods Fundamentals and
Applications, 2nd Ed. 2001, Wiley, New Jersey,
USA.
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Most Efficient DSSC (11.1)

• J-V and Power curves

• Incident radiation 100 mW/cm2
• TiO2 semiconductor
• Dye sensitizer
• I- /I3- in ionic liquid electrolyte

JSC 20.9 mA/cm2 VOC 0.736 V
L. Han. et al. J. Jpn. Appl. Phys. 2006, 45, L638
L640.
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Make your own solar cell at home

• http//www.youtube.com/watch?vbVwzJEhMmD8feature
  player_embedded

• http//www.wired.co.uk/magazine/archive/2010/03/ho
  w-to/how-to-make-your-own-solar-cell-

Retrieved 8th March 2012
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Current Products
Sonys functional Hana-Akari DSSC lanterns.
G24 Innovations Back pack DSSC 0.5W under direct
sunlight. Claims 12 efficiency.
P. Patel Dye-Sensitized Solar to Go in
Technology Review October 2009, MIT Publications.
Retrieved 18th March 2010 Sony design.
http//www.sony.net/Fun/design/activity/sustainabl
e/dssc.html. Retrieved 18th March 2010.
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Additional References
http//www.itechnews.net /tag/solar-panel/ Retriev
ed 16th March 2010
http//solarpanelspower.net /solar-panels/miniatur
e-pv-cells Retrieved 16th March 2010
NRC PV Potential Interactive map,
glfc.cfsnet.nfis.org/mapserver/pv/index.php?lange
. Retrieved 18th March 2010. Electricity
Statistics. http//www.energy.alberta.ca/Electrici
ty/682.asp. Retrieved 18th March 2010.
http//www.ecf.utoronto.ca /luzheng/research.html
Retrieved 16th March 2010