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Plasmonic and Photonic Photovoltaics based on graphene and other carbon nanostructures
Fengli Wang, Guowei Xu, Jianwei Liu, Caitlin Rochford, Judy Wu Department of Physics and Astronomy, University of Kansas In collaboration with Cindy Berrie, and Tina Edwards Department of Chemistry, University of Kansas Jun Li Department of Chemistry, Kansas State University Ron Hui, Qian Wang Department of Electrical Engineering and Computer Science Francis D’Souza, and Navaneetha Krishnan Department of Chemistry, Wichita State University
NSF EPSCoR Kansas Center for Solar Energy Research Annual Program Review June 12-14, 2011
Three Generations of Solar Cells I) Wafer based Silicon Lab record: 25% Module record: 23% II) Thin-film Different semiconductor(s) Reduced material cost Lab record: 26% (GaAs) 17% (CdTe) 10% (a-Si) Module record: 20% (pc-Si) III) Advanced thin-film Circumvent 1st gen.
theoretical limit Maintain low cost Lab record: 34% (tandem) Module record: ---
Projections:
Goals: ~ 30¢/WP
~ 2¢/kWh
0 100 200 300 400 500
20
40
60
80
100
Cost, US$/m2
Effic
ienc
y, %
US$2.50/W
US$0.20/W US$0.10/W
Shockley- Queisser limit
Ultimate thermodynamic limit at 1 sun
Ultimate thermodynamic limit at 46200 suns
I
III
II
Enhance efficiency Reduce cost
Principle of Semiconductor Solar Cells
Manipulation of photon absorption and electron transport at nanoscale is the key to high efficiency and low cost PV devices.
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CNF/TiO2 nanowire Dia: 90-140 nm Spacing between probes: 1-1.5 µm
Conductivity and Photoconductivity
Crystallinity in TiO2 shell critical to photocurrent transport Improved dark conductivity and photoconductivity in annealed sample
0 10 20 30 400.00.20.40.60.81.01.21.4
S1, Dark S1, 1 Sun S2, Dark S2, 1 Sun
Curre
nt (µ
A)
Voltage (mV)
0 10 20 30 400.00.20.40.60.81.01.21.4
S1, with Dye, Dark S1, with Dye, 1 Sun S2, with Dye, Dark S2, with Dye, 1 Sun
Curre
nt (µ
A)
Voltage (mV)
annealed
annealed
Rochford, C.; et al,. Applied Physics Letters 2010, 97 (4), 043102.
hν COOH
COOH
Z.Z. Li et al, Nanoscale Research Letters 2010, 5, 1480.
Li-KSU and Wu-KU
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Photonic and Plasmonic photovoltaic
Atwater and Polman, Nat. Mat. Feb. 2010 | doi: 10.1038/nmat2629
Enhanced light absorption via promoted light interaction with photonic or/and plasmonic nanostructures
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-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-0.0100
-0.0075
-0.0050
-0.0025
0.0000
0.0025wieght line - patterned light line - unpatterned
22 mW 32 mW 72 mW 105 mW
Curr
ent D
ensi
ty (A
/cm
2 )
Potential (V)Diffraction effect after N3 dye
Photonic dye-sensitized solar cells Hui, Wu—KU, D’Souza-WSU)
Efficiency improved dramatically F.L. Wang et al, preprint.
Photonic FTO
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(a)
TiO2
FTO
Silver particles
On-going work: plasmonic+photonic transparent electrodes
0 0.5 1 1.5 2 2.5 30.5
0.6
0.7
0.8
0.9
1
Depth into TiO2 layer (µm)
Nor
mal
ized
Pow
er a
bsor
ptio
n
Flat interface
With FTO hemisphere
With FTO hemisphere and silver nano particles
Poster by F.L. Wang et al
Ag nanoparticles on FTO photonic crystals
Plasmonic graphene-based solar cells in collaboration with Berrie, Hui, Li, D’Souza
National Renewable Energy lab, Argonne Nat. lab, Oak Ridge Nat. lab, Iowa State Univ., Univ. of Arkansas
• Ultra-thin • Low cost • Abundance of carbon • Compatible thermal
budget to that of Si (nc and amorphous) films
Advantages of graphene: • Improved light scattering
required for thin film PVs • Interface between graphene
and PV materials • Industrialization
Issues:
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Graphene: a promising transparent electrode • Massless Dirac fermions with high Fermi speed
Vf~106 m/s • high mobility μ ~106 cm2/Vs • σ=enμ—high conductivity σ at low carrier density n
due to high μ; σmin ~4e2/h even at low carrier density
Optical Properties of Graphene • Gapless semiconductor or semi-metal • Fresnel equation in thin film limit: Transmittance—
Absorption –
Reflection – <0.1%
• Transparent conductors • IR detectors • Bio-/chemical-sensors
10 P. Avouris, Nano Letters 10, 4285(2010)
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Graphene photonic crystals
Fabricated using nanoimprint lithography
J.W. Li, et al, APL (accepted with minor revisions) and poster by Jianwei Liu et al
Optical Transmittance
Electrical Conductivity
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Transmittance vs. conductivity
A unique scheme to improve both optical transmittance (broad band) and electrical conductivity
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Ag nanoparticles on graphene: • sheet resistance reduced by 2-4 times • light scattering for enhanced absorption at small
solar cell thickness
Plasmonic graphene: low-cost and high performance PVs In collaboration with NREL, KSU (Li), Hui and Berrie (KU), D’Souza (WSU)
Si
Silver hemisphere 1nm thick graphene
Plane wave illumination
300
nm
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Self-assembled Ag nanoparticles on graphene Diameter: 30-80nm
Ordered Ag nanoparticles on graphene Diameter: 150-250nm
A large range of controlled geometry has been demonstrated.
Generating plasmonic graphene
Poster by Guowei Xu et al, preprint.
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• 10 times enhanced Raman peaks suggest strong light scattering on plasmonic graphene
• Confirmation of light scattering also in transmission spectra
• 2-4 times enhanced conductivity
Enhanced light scattering in plasmonic Graphene
300 400 500 600 700 8000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
G_14nm AgNPs G_8nm AgNPs G_4nm AgNPs
Tran
smitt
ance
Wavelength (nm)
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Summary Carbon-based nanostructures provide a fascinating system for physics studies and are promising for many optical and opto-electronic applications
University of Kansas Thin Film and Nanoscience Group July 27, 2010
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Dr. Jianwei Liu Guowei Xu Caitlin Rochford Dr. Rongtao Lu Dr. Fengli Wang Dr. Bing Li Caleb Christianson Alan Elliot Gary Melek Logan Wille Mike Dunaway Jon Gregory Richard Lu
External collaborations: ANL: Zhijun Chen and Vic Maroni LANL: Javier Baca ORNL: Amit Goyal and Parans Paranthaman NREL: Yanfa Yan
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