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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

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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