of 22
7/27/2019 2010 Physical Science Session - Fan
1/22
Flexible Dye-Sensitized Solar Cells on Al Foils
Jon Linville, Tyler Spurlock, Matthew Seitz and Xiaojuan (Judy) Fan
Department of Physics, Marshall University, Huntington, WV 25755
STAR Symposium, 2010, WV
http://www.siliconsolar.com/
*Email address: [email protected]
7/27/2019 2010 Physical Science Session - Fan
2/22
Si crystals: need to be produced in a vacuum.
Thin film solar cells: Si, CdTe; GaAs, GaN, InN,
Cu(In,Ga)Se2 flexible solar cell modules (commercialized)
Dye-sensitized solar cells (DSSC)
Brief Review: Photovoltaic Solar Cells
ORegan and Grtzel, 1991
Cell Components:Porous nanocrystalline TiO2Organic dye molecules Iodine/Iodide electrolyte
11% efficiency has been demonstrated in lab Ready to the market
Question: Can we make flexible DSSCs?
Yes
7/27/2019 2010 Physical Science Session - Fan
3/22
The 3rd generation Solar Cells: DSSCs
Dye-sensitized solar cells (DSSCs): electrochemistry
Key components: Metal oxide nanostructures Organic light sensitizer: dye molecules Electrolyte with
3/II
Advantage:Low cost, solution process, and environmental friendly
Disadvantage:Low efficiency (
7/27/2019 2010 Physical Science Session - Fan
4/22
hvI- I3
-+ e
Dye
TiO2
I- I3-+ ee
e
e
e
Load
e
1. Light absorbed by dye
2. Excited electrons injected into
nanoparticles
3. Electrons percolate to external
load to reach the counter
electrode
4. Electrons are transferred totri-iodide to yield iodide
5. The iodide reduces dye to
its original state.
How DSSC Works
e
ee
7/27/2019 2010 Physical Science Session - Fan
5/22
Printed Flexible Dye-Sensitized Solar Cells (DSSC)
Very recently, news from Japan'sToin University of Yokohama
DSSC in a flexible A4 sheet.
Solar conversion efficiency: 6%(Solar cells on market: 15%)
AdvantagesCheaper to makeFlexibility
Simply be printed in airOnly 0.4mm-thick, used for a laptop PC or rolled and foldedfor storage.
7/27/2019 2010 Physical Science Session - Fan
6/22
Solar Cell Fabrication Technology
High vacuum deposition: p-njunctions Sputtering deposition Thermal evaporation
E-beam evaporation Pulsed laser deposition Molecular beam epitaxial
Ribbon and roll-to-roll coating on flexible substrates
Dye-sensitized solar cells (DSSCs): no vacuum needed Nanoparticle paste
Sol-gel-dip-coating
Screen printing
Spray pyrolysis
Compression
Polymer assisted
The new organic
solar cells are light
and flexible.
Credit:
Nicole Cappello,
Georgia Institute of
Technology
Silicon Solar Inc.
7/27/2019 2010 Physical Science Session - Fan
7/22
Mesoporous TiO2
Nanoparticle paste and hydrothermal at 230CGratzel, M. J. Photochem. And Photobio. A 164
(2004) 3-14
TiO2: must bePorous: large surface area toattach more dye moleculesTiO
2nanoparticles
Porosity > 50%Other metal oxides can beused, ZnO, SnO2,
TiO2, easy synthesis,abundant, inexpensive
50 nm
K. M. Gopal, et al,Adv. Funct. Mater,15, 2005, 1291-1296
Thermal evaporation 500C rf sputtering Ti anodized in HF
7/27/2019 2010 Physical Science Session - Fan
8/22
TiO2: A large band gap semiconductor
A large bandgap semiconductor (~3.2 eV)
Absorption edge is in ultraviolet (UV), Not responsible for sun light absorption in solar cells
Rutile
Anatase
Brookite
National Renewable Energy
Laboratory, Golden, Colorado
Materials Characterization
Laboratory, Penn State
7/27/2019 2010 Physical Science Session - Fan
9/22
Unique route to generateporous TiO
2thin films
Our Approach:
Polymer assisted Ti alkoxides Solvents Stable precursors Spin coating (stable in air)
Thermal sintering Polymer removed Mesoporous TiO2
solvent Ti alkoxides
PMMA: (MW 350,000)poly(methyl methacrylate)
(C5O2H8)n
Ti n-butoxide
Ti[O(CH2)3CH3]4
7/27/2019 2010 Physical Science Session - Fan
10/22
6 % (w/v) PMMA +
6% (w/v)
Ti(OnBu)4
2 % (w/v) PMMA +
6% (w/v) Ti(OnBu)4
SEM images: double-layer structure
(a) (b)
(c) (d)
4 % (w/v) PMMA +
6% (w/v)
Ti(OnBu)4
8 % (w/v) PMMA+ 6% (w/v)
Ti(OnBu)4
1 m
7/27/2019 2010 Physical Science Session - Fan
11/22
Porous TiO2 Thin Films: Structure and Morphology
25 nm
100 20 nm
(b)(a)
X-ray diffraction: anatase phase
Particle size: 25nm
AFM image
Anatase structure is often preferred to rutile in the
application of TiO2 in DSSC in terms of lattice packing.[Park, et al.J. Phys. Chem. B 2000, 104, 8989-8994]
7/27/2019 2010 Physical Science Session - Fan
12/22
Thin Film X-Ray Reflectivity Analysis
10-5
10-4
10-3
10-2
10-1
100
Reflect
ivity
86420
2/ (degree)
Decay of reflectivity
Surface roughness
Decay of amplitude
Interface roughness
Period of oscillation
Thickness d
Amplitude of oscillation
Contrast of density
Critical angle c
Density density 1density 2
density 3
thickness d1thickness d2
roughness 1roughness 2roughness 3
Oscillatory behavior known as Kiessig fringes.
thickness, density, and roughness
7/27/2019 2010 Physical Science Session - Fan
13/22
TiO2 thin film thickness, roughness, and density
Layer No.Layer
Name
Density
(g/cm3
)
Thickness
(nm)
Roughness
(nm)
1
2
Si
TiO2
2.3300
2.6727
N/A
18.506
0.489
0.579
Table 1. Density, thickness and roughness of sample 4 from XRR data.
For nonporous anatase TiO2
0
/1 =rP
Relative porosity: Pr = 33%
0 ~ 3.9 g/cm3,
X-ray Reflectivity
7/27/2019 2010 Physical Science Session - Fan
14/22
Dye Molecule we used
Meso-tetra(4-carboxyphenyl)porphyrin (TCPP), T790
Color: Red brown
Absorption: 400 450 nm region, 500 700 nm region
Adsorbs strongly onto nanoparticulate TiO2 and serves as an
efficient photosensitizer. [J. Phys. Chem, 104, 3624 (2000)]
450 500 550 600 650 7000.0
0.5
1.0
1.5
2.0
2.5
Absorban
ce
Wavelength, nm
Dye: TCPP in EtOH solution
7/27/2019 2010 Physical Science Session - Fan
15/22
Gel Electrolyte: Polymer Matrix
Polymer electrolyte we used
Poly(ethylene glycol) (PEG), (MW 20,000)
100 mM KI, 50 mM I2 Solvents including:
ethylene carbonate (80% v/v)
o Transparent crystal-like solid, at T= 25 C
o Colorless liquid at T = 34 - 37 C
propylene carbonate (20% v/v)
o Colorless liquid
C2n
H4n+2
On+1
PEG
Advantages:Avoid liquid leakageAny shape membrane
Hydro gel
electrolyte
7/27/2019 2010 Physical Science Session - Fan
16/22
0.0 0.2 0.4 0.6 0.8 1.00
5
10
15
20
Isc
Voc
Curren
tDensity(m
A/cm
2)
Bias Voltage (V)
ImV
m
Maximum Power Point
To Characterize Solar Cells
Photo electricity conversion efficiency:
mmmVIP
=
Cell Maximum Power:
Incident Light Power: Ps
Short Circuit Current:Isc
Open Circuit Voltage: Voc
ocsc
mm
VI
VIFF=Fill Factor FF:
s
ocsc
P
FFVI=
7/27/2019 2010 Physical Science Session - Fan
17/22
Photo-Electricity Conversion Efficiency
I-VCurves under one Sun (AM1.5 global, 100 mW/cm2) and Dark.
Isc = 3.03 mA/cm2, Voc = 1.18 V, = 2.05%
OCSC
mpmp
VI
VIFF=
light
OCSC
P
FFVI
=
Conversion efficiency:
Fill Factor:
7/27/2019 2010 Physical Science Session - Fan
18/22
Several factors: Nanoparticle imbedded electrolyte Different Dye molecules (N3 instead of T790)
Porous TiO2 with high ratio polymer template
Efficiency improvement > 200%
0.0 0.2 0.4 0.6 0.8
0
1
2
3
4
5
6
7
8
Currentdensity(mA/c
m2)
Voltage(V)
7/27/2019 2010 Physical Science Session - Fan
19/22
Electrolyte: Imidazolium+I2 + PEO,solid texture phase
Flexible Dye-Sensitized Solar Cells
Cheap Dye: Basic Red 1,Rhodamine 6GDN
Formula: C28H31CIN2O3,red to brown in color.
Anode electrode:porous TiO2 on Al foil
7/27/2019 2010 Physical Science Session - Fan
20/22
Photo-Electricity Conversion Efficiency
Flexible solar cell on Al Foil
Al foil
Porous TiO2
Solid Electrolyte
Conductive PET sheet
Back Illumination
7/27/2019 2010 Physical Science Session - Fan
21/22
7/27/2019 2010 Physical Science Session - Fan
22/22
Funding Support:NSF-MU ADVANCE GrantNASA WV EPSCoR Seed Grant
NASA Undergraduate Research GrantMarshall University Research Corporate
Undergraduate Researchers:Matthew Seitz, SophomoreTyler Spurlock, Sophomore
Jon Linville, Senior
Thank you for your attention!
Acknowledgements: