This document summarizes research on using the polymer dye ET 30 as a sensitizer in dye-sensitized solar cells (DSSC). The objectives were to evaluate ET 30's suitability and use electrochemical impedance spectroscopy (EIS) to characterize DSSC performance. Two versions of ET 30 cells were tested alongside reference Ru dye cells. EIS results showed potential differences between the cells. However, further optimization of ET 30 loading and indoor light spectrum are needed before definitive conclusions can be drawn about ET 30's effectiveness from EIS measurements. Future work will involve optimization, using a standard light spectrum, and developing an equivalent circuit model.

1. Electrochemical Impedance of
Dye sensitized solar cells
Chetan Chaudhari
Graduate Research Assistant,
Arizona State University.
Coauthored by
Chih-yu Jen, C. Park, S.Franklin, Dr. S.Petrovic,
Dr. Munukutla.
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2. Outline
• Objectives
• Dye sensitized solar cells (DSSC)
• Impedance Spectroscopy on DSSC -Earlier work
• Polymer dye ET 30 (Reichardt’s dye)
• Experimental Procedure
• Performance
• Results using Electrochemical Impedance Spectroscopy
• Challenges
• Conclusions
• Future work
• Acknowledgements 2

3. Objectives
• Evaluate the suitability of the polymer dye ET 30 as a
sensitizer with mesoporous TiO2
• Demonstrate Electrochemical Impedance
Spectroscopy (EIS) as an effective and rapid
technique to characterize performance of Dye
Sensitized Solar Cell (DSSC)
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4. DSSC – Dye sensitized solar cells
• Since 1990s (What do you
mean?) remove this bullet.
• Reported efficiencies around
10%
• Excited electrons from
oxidized dye render the
semiconductor conduction
• Further, dye oxidizes the
mediator redox couple.
• Redox couple regenerated by
the electron collected at the
through cathode.
Source : M.Grätzel, Nature 414, 338-344 (2001)
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5. Polymer based DSSC
• Replacement of Ru based dye
– Reason : An Opinion that Ru based compounds are highly
toxic and carcinogenic (Source :Institute of Science and Society)
• Potential for being
– Cheaper
– Designable on molecular level
– Disposable
– Environmentally benign 5

6. Previous work
• Modeling of an equivalent circuit (with a
diode) for DSSC – Liyuan Han et al., Sharp corp. [DOI: 10.1063/1.1690495] (2005)
• Modeling and interpretation of electrical
impedance spectra of DSSC operated under
open circuit conditions – R. Kern et al., Freilburg Materials Research
center, Germany. (2002)
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7. ET 30 (Reichardt’s dye)
• 2,6-Diphenyl-4-(2,4,6-
triphenylpyridinio)phenolate
• Solvatochromatic dye
• Extreme sensitivity of the
absorption spectrum to small
changes in the medium polarity
• Absorption spectrum with ACN –
Acetonitrile
Fletcher et al, Behavior of the solvatochromic
probes, (2001)
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8. Define the cell area
by masking on
Working Electrode
(WE)
Step 1
Coat TiO2 on WEStep 2
Immerse in
Dye+Solvent
Step 3
Deposit Platinum
paste on Counter
Electrode
Step 4
Clean both
Electrodes
Step 5
Seal ElectrodesStep 6
Inject Electrolyte
(Iodolyte)
Step 7
Paint contacts
with Silver paint
Step 8
Day1
(0.5hr)
Day1 (2hr)
Day2 (15hr)
Day2 (1hr)
Day3 (0.5hr)
Day3 (0.5hr)
Day4 (0.2hr)
Day4
Cell Fabrication Procedure
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9. Performance Testing
Ground of the potentiostat
to the Faraday’s cage
Tungsten
Halogen lamp
800 W/m2
DSSC
under
test
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10. Performance Results
Dye – ET 30
Cell Area – 6 cm2
Version 1 – IPA as
solvent + Lower loading
Version 2 – ACN as
solvent + Higher
loading
ET 30 Cell
Dye – Ru 535
Cell Area – 6 cm2
Ru Cell
Dye – Ru 535
Cell area – 2.64 cm2
No of cells – 5
Prefab cell
Referred as 10

11. Performance Results
mA V V cm2 mA/cm2 mW/cm2
Cell Isc Voc Voc/cell Area Isc/Area PD (FF=1)
Max
possible
Efficiency
Tungsten
Halogen Prefab old 2.580 2.740 0.548 2.640 0.977 0.536 0.669
800 W/m2 Prefab new 1.110 2.910 0.582 2.640 0.420 0.245 0.306
Ru Cell 5.020 0.554 0.554 6.000 0.837 0.464 0.579
ET30 old 0.014 0.100 0.100 6.000 0.002 0.000 0.000
ET30 new 0.550 0.358 0.358 6.000 0.092 0.033 0.041
Sunlight Prefab old 8.200 3.160 0.632 2.640 3.106 1.963 2.454
800 W/m2 Prefab new 7.700 3.380 0.676 2.640 2.917 1.972 2.465
Ru Cell 17.000 0.633 0.633 6.000 2.833 1.794 2.242
ET30 old 0.120 0.230 0.230 6.000 0.020 0.005 0.006
ET30 new 1.730 0.425 0.425 6.000 0.288 0.123 0.15311

12. Current –Voltage curve under
800W/m2 using a Potentiostat
Ru Cell ET30 cell
Voc = 0.554V
Isc = 5.02 mA
Voc = 0.358 V
Isc = 0.55 mA
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13. Impedance Spectroscopy Results
• Solid Lines – Impedance plot , Dotted - Phase
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14. Ru and ET 30 Cells
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15. Ru and ET30 cells
• Under 800W/m2
• Possible hint of difference in Higher
frequencies 15

16. ET 30 Cell – version 1 & 2
Green – Version 1 (Lower loading)
Blue – Version 2 (Higher loading)
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17. Challenges
• Poor Indoor spectrum
(class C ) with Halogen
Lamp
• ET30
– Inorganic Dye not
readily attachable to
TiO2
– Nafion : Possible
inhibition to electron
transfer
Natural sunlight
Halogen lamp
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18. Conclusions
• ET 30 has potential to be used in DSSC with
optimization of loading and better binding with the
charge separator.
• With Using Electrochemical Impedance
Spectroscopy, equivalent circuit modeling possible
but the data is still being analyzed.
• Concerns about the spectrum of the light.
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19. Future Work
• Optimization of loading of ET30 and the solvent
polarity.
• Use of Class A spectrum for Performance
measurement and characterization.
• Development of Equivalent circuit model to establish
convert the observations into definite conclusions.
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20. Acknowledgements
• The work is partially supported by the Arizona Institute of
Renewable Energy, Arizona State University.
• We would like to acknowledge and thank Dr. Mani,
Professor, Arizona State University for valuable discussions
related to the project.
Thank you!
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