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Dye-SensitizedSolar Cells
Carl C. WamserPortland State University
Nanomaterials Course - June 28, 2006
Energy & Global WarmingEnergy & Global Warming
•• M.I. Hoffert et al., M.I. Hoffert et al., NatureNature, 1998, , 1998, 395395, p 881, p 881““Energy Implications of Future Atmospheric Energy Implications of Future Atmospheric Stabilization of COStabilization of CO22 ContentContent””
•• M.I. Hoffert et al., M.I. Hoffert et al., ScienceScience, 2002, , 2002, 298298, p 981, p 981““Advanced Technology Paths to Global Climate Stability: Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse PlanetEnergy for a Greenhouse Planet””
The Kaya IdentityThe Kaya Identity
•• N N = population= population•• GDP/N GDP/N = gross domestic product per person= gross domestic product per person•• E/GDP E/GDP = energy intensity (per GDP unit)= energy intensity (per GDP unit)•• C/EC/E = carbon intensity (per energy unit)= carbon intensity (per energy unit)
Annual Energy = N*(GDP/N)*(E/GDP)Annual Energy = N*(GDP/N)*(E/GDP)
Annual COAnnual CO22 = N*(GDP/N)*(E/GDP)*(C/E)= N*(GDP/N)*(E/GDP)*(C/E)
Global Totals/Future TrendsGlobal Totals/Future Trends
Annual Energy = N*(GDP/N)*(E/GDP)Annual Energy = N*(GDP/N)*(E/GDP)
5.3 billion5.3 billion~9 billion ~9 billion by 2050by 2050
$4100$4100risingrising
1.6%/yr1.6%/yr
4.3 kWh/$4.3 kWh/$fallingfalling
1.0%/yr1.0%/yr
64 gC/kWh64 gC/kWhfallingfallingby ??by ??
Annual COAnnual CO22 = N*(GDP/N)*(E/GDP)*(C/E)= N*(GDP/N)*(E/GDP)*(C/E)
10 TW10 TW3030--40 TW40 TWby 2050by 2050
( 1990 data cited in ( 1990 data cited in HoffertHoffert’’ss Nature paper )Nature paper )
6 Gtons6 Gtons350 ppm350 ppm
rising to ??rising to ??
ConclusionsConclusions
Stabilization of atmospheric carbon Stabilization of atmospheric carbon will require immense amounts of will require immense amounts of carboncarbon--free energy in the near future free energy in the near future (2050):(2050):
•• 550 ppm 550 ppm -- about 15 TWabout 15 TW
•• 450 ppm 450 ppm -- about 25 TWabout 25 TW
•• 350 ppm 350 ppm -- over 30 TWover 30 TW
M.I. Hoffert et al., M.I. Hoffert et al., NatureNature, , 19981998, , 395395, p 881, p 881
05
101520253035404550
Oil
Coal GasFiss
ionBiom
assHyd
roelec
tric
Solar, w
ind, g
eothe
rmal
0.5%
Source: Internatinal Energy Agency
2002
Sources of Energy Supply - Worldwide
05
1015
202530
3540
4550
Oil
Coal
GasFiss
ionBiom
assHyd
roelec
tric
Solar, w
ind, g
eothe
rmal
2050
13 Terawatts 30-50 Terawatts
The ENERGY REVOLUTION(The Terawatt Challenge)
Partners in ScienceJanuary 18, 2003
R. E. SmalleyRice University
ConclusionsConclusions
““Researching, developing and Researching, developing and commercializing carboncommercializing carbon--free primary power free primary power technologies capable of 10technologies capable of 10--30 TW by the mid30 TW by the mid--21st century could require efforts, perhaps 21st century could require efforts, perhaps international, pursued with the urgency of the international, pursued with the urgency of the Manhattan Project or the Apollo space Manhattan Project or the Apollo space programme.programme.””
M.I. Hoffert et al., M.I. Hoffert et al., NatureNature, , 19981998, , 395395, p 881, p 881
Photovoltaic Land Area Requirements
20 TW
3 TW
Graphic fromNate LewisCaltech
3 TW= approx
total energycurrently
used in U.S.
20 TW= minimum carbon-freetotal energyneeded by
2050
6 Boxes at 3.3 TW Each
Photovoltaic Land Area Requirements
PhotosynthesisPhotosynthesis( 1961 Nobel Prize )( 1961 Nobel Prize )
Photosynthetic Reaction CenterPhotosynthetic Reaction Center
http://www.mpibp-frankfurt.mpg.de/~michael.hutter/rcenter.html
( 1988 Nobel Prize )( 1988 Nobel Prize )
Artificial PhotosynthesisArtificial Photosynthesis
Any solar energy conversion method that uses some aspects of nature’s strategy, compounds, or both
StrategyPhotoinduced Photoinduced
electron transfer electron transfer across a membraneacross a membrane
CompoundsChlorophyll dyes Chlorophyll dyes
and electronand electron--transfer mediatorstransfer mediators
Thermodynamic CriteriaThermodynamic Criteria
Optimize energy conversion (photopotential)
– Match the dye bandgap to the solar spectrumoptimum λbg ~ 1000 nm, efficiency ~ 30%
– Match the redox potentials (valence/conduction bands)
hν
e-
h+
ETM HTMdye
Kinetic CriteriaKinetic Criteria
Optimize quantum yield (photocurrent)
• Fast forward reactions:a) Light absorptionb) Charge separationc) Hole and electron mobilities
• Slow back reactions:d) Excited state deactivatione) Charge neutralization ETM HTMdye
DyeDye--Sensitized Solar CellSensitized Solar Cell
• Dyes– Ru(bipy)3 derivatives (N3)– Porphyrins
• Electron-transport media– n-type semiconductors– Nanoparticulate TiO2
• Hole-transport media– p-type semiconductors
– Redox electrolytes ( I- / I3- )
– Conductive polymers
The The GrGräätzel tzel
CellCell
B. O’Regan &M. Grätzel, Nature (1991) 353, 737-740.
TiO2 I-/I3-N3
~
-0.6-0.9
+0.8
+0.2
( V vs SCE )Optimized output
– Short-circuit currentIsc ~ 20 mA/cm2
– Open-circuit voltageVoc ~ 0.7 V
– Quantum yield ~ 1
– Efficiency ~ 11%
The GrThe Gräätzel Celltzel Cell
I-/I3-
Preparation of a Grätzel CellPreparation of a Grätzel Cell
ITO
or
FTO
ITO
or
FTO
TiO2 Porphyrin
hνISC ~ 20 mA/cm2
VOC ~ 0.7 Volts
Φ ~ 1
Efficiency ~ 11%
Operation of a Grätzel CellOperation of a Grätzel Cell
ITO TiO2 TCPP
-0.9
+1.1
+2.6
-0.6
Voc = 0.7 V ; Isc = 20 mA/cm2
I3 / I ITO
+0.2
- -
hv
Porphyrin LUMO
Porphyrin HOMOPP++
Photopolymerization Photopolymerization -- Proposed MechanismProposed Mechanism
HN
N
N
NH
NH2
COOHHOOC
HOOC
N
N
N
H
H H
N
5,10,15-tris(4-carboxyphenyl)-20-(4-aminophenyl)porphyrin (TC3APP)
H
e-hv
NH2 NH2
n
Stage II
e-
e-
Stage I10n H+
5n H2
e-TiO2
x10
DSSC Expt: ProceduresDSSC Expt: Procedures
1. Prepare Working ElectrodeTiO2 underlayer / nanoparticles / overlayer
Dye adsorption ( TCPP in EtOH )
2. Prepare Counter ElectrodeGraphite on FTO (F-doped tin oxide)
3. Assemble Cell
Redox electrolyte solution ( I-
/ I3-
)
4. Irradiate CellMonitor light intensity / photocurrent / photovoltage
DSSC Expt: ProceduresDSSC Expt: Procedures1. Prepare Working Electrode
TiO2 underlayer - dip in Ti(iOPr)4
Nanoparticle layer - dip in TiO2 slurry
Overlayer (skipped this time)
Bake at 450° for 30 minutes
( A pre-prepared electrode will be provided for testing while your electrode is baking )
DSSC Expt: ProceduresDSSC Expt: Procedures
2. Prepare Counter Electrode
Graphite on FTO (F-doped tin oxide)
(catalyst for iodide/triiodide reaction )
DSSC Expt: ProceduresDSSC Expt: Procedures
3. Dye Adsorption
Pre-prepared electrode will have TCPP, adsorbed from EtOH (takes overnight)
You will soak your electrode in blackberry juice
(natural anthocyanine dyes)
takes about 15 minutes
DSSC Expt: ProceduresDSSC Expt: Procedures
4. Assemble CellWorking electrode (with dye)
a) TCPP pre-prepared electrode
b) Blackberry electrode, rinsed and dried
Add redox electrolyte solution ( I- / I3- )
Assemble sandwich cell
Slide and back electrode in test fixture
DSSC Expt: ProceduresDSSC Expt: Procedures
5. Irradiate CellInstall cell in test fixture Install test fixture in Vertical Optical Bench
(VOB)Scan applied voltage from -700 to +100 mVMonitor light intensity Monitor photocurrent vs. applied voltage
(iV curve)Capture data on PC, export to ExcelSave to your personal USB drive
Slide being tested in the VOB
Light from the VOB Through 16mm hole
Light shining through test slide
Cell being tested on VOB
iV Curve for TCPP Cell
Re-Test of KJ0216 NB-90-21 KJ216_22 DipCoat FKJ0172 Pt (NB-80-85)
-100100300500700900
110013001500
-800 -700 -600 -500 -400 -300 -200 -100 0 100mVolts
mic
roA
mps
Power Curve for TCPP Cell
Re-Test of KJ0216 NB-90-21 KJ216_22 DipCoat FKJ0172 Pt (NB-80-85)
0.0000
0.1000
0.2000
0.3000
0.4000
0.5000
0.6000
-800 -700 -600 -500 -400 -300 -200 -100 0 100
mVolts
mW
atts
iV Curve for TCPP Cell
Re-Test of KJ0216 NB-90-21 KJ216_22 DipCoat FKJ0172 Pt (NB-80-85)
-100100300500700900
110013001500
-800 -700 -600 -500 -400 -300 -200 -100 0 100mVolts
mic
roA
mps
Voc
IscPmax
Fill Factor
Test and Performance Parameters• Light source: Tungsten halide lamp
Intensity = 97 mW/cm2 = 0.97 Sun• Irradiated area = 0.71 cm2
• Pin = 69 mW• Voc = 652 mV• Isc = 1.3 mA• Pmax = 0.47 mW• Fill Factor = Pmax / ( Voc * Isc ) = 0.55• Efficiency = Pmax / Pin = 0.68 %
DSSC Expt: ReportDSSC Expt: Report
Check the class website for updated info
Title / AbstractIntroduction / BackgroundExperimental Procedure / ApparatusResults / DiscussionConclusions
Compare all performance data for both types of cells you tested
DSSC DSSC Expt: ReferencesExpt: References“Demonstrating Electron Transfer and Nanotechnology:
A Natural Dye-Sensitized Nanocrystalline EnergyConverter”, G. P. Smestad and M. Grätzel, J. Chem. Educ., 1998, 75(6), 752-756.
“Adsorption and Photoactivity of Tetra(4-carboxyphenyl)porphyrin on Nanoparticulate TiO2”, S. Cherian and C. C. Wamser, J. Phys. Chem. B, 2000, 104, 3624-3629.
“Basic Research Needs for Solar Energy Conversion”, U.S. Department of Energy, 2005.
Note - all of the above references can be found as .pdf files on Professor Wamser’s website:
http://chem.pdx.edu/~wamserc/Research/