6 albert polman fom-institute amolf amsterdam

7/29/2019 6 Albert Polman FOM-Institute AMOLF Amsterdam

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Plasmonic thin-film solar cells

Albert Polman

Center for NanophotonicsFOM-Institute AMOLF

Amsterdam, The Netherlands


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CALTECH

AMOLF

UNSW

ANU

Harry Atwater

Vivian Ferry

Kylie CatchpoleFiona BeckSuddha Mokapati

Utrecht University

Philips Research

Ruud SchroppHongbo LiMarc Verschuuren

Ewold Verhagen, Maarten HebbinkClaire van Lare, Rene de Waele


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Black dots:

area of solarpanels neededto generate allof the worlds

energyassuming 8%efficient

photovoltaics

Solar irradiance on earth


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Light is poorly absorbed in a thin-film solar cell

Solar spectrumabsorbed in 2 mthick Si


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Re la t i ve abun dance of e l em en ts vs . at om ic n r .

from P.H. Stauffer et al, Rare Earth Elements -Critical Resources for High Technology, USGS (2002)

Materials resources are limited

So lu t ions :

1) Earth AbundantSemiconductors(Si,Cu2O, Zn3P2, FeS2)

2) Enhance LightAbsorption/reducesemiconductorvolume

Requirements to construct1 TW of PV with opticallythick cells at 15% efficiency


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Light trapping by surface plasmons

Metal nanoparticlesurface coatings

Textured metalbackcontacts


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Light scattering

p

Rayleigh scatteringfrom point dipole Scattering from point dipoleabove a substrate

Preferentialscatteringinto high-index

substrate

See, e.g.: J. Mertz, JOSA-B 1 7 , 1906 (2000)

4 %

96 %


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Light trapping using particle plasmons

Goal: Increased efficiency

- IR absorption (higher Isc)- carrier collection (higher Voc)and/or

Reduced thickness (=cost)

fsubs fsubs

fair


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Metal nanoparticle scattering

Cross section > 1 All light captured and scatteredinto substrate (=AR coating)


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From point dipole to particle plasmon

500 550 600 650 700 750 8000

0.2

0.4

0.6

0.8

1

Wavelength (nm)

F

ractionscatteredintosubstrate

dipole

cylinder

hemisphere

sphere 100nm

sphere 150nm

500 550 600 650 700 750 8000

0.2

0.4

0.6

0.8

1

Wavelength (nm)

F

ractionscatteredintosubstrate

dipole

cylinder

hemisphere

sphere 100nm

sphere 150nm

Fraction scattered into substrate highest forcylinder & hemisphere:strongest near-field coupling

Ohmic damping V, scattering V2,

Tradeoff: larger size more scattering,but lower coupling

96 %

0

FDTDcalculations

Kylie Catchpole

Appl. Phys. Lett. 9 3 , 191113 (2008), Opt. Expr. 1 6 , 21793 (2008)


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Scattering cross-section varies with dielectric spacer

scat normalized to particle areaLarger spacing:

Interference in driving

fieldBut:lower coupling fraction

(+ local density of statesvariation modifies albedo)

500 600 700 800 900 10000

2

4

6

8

10

12

14

wavelength (nm)

Qscat,

Qsubs

30nm

10nm

30 nm

10 nm

D

Q

tot

sub

Kylie Catchpole



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Maximum path length enhancement

Highest path length

enhancement forcylinder and hemisphere

Geometric series

fsubs fsubs

fair

0.6 0.7 0.8 0.9 11

10

100

fraction into substrate

maximump

athlengthenhancement

sphere 150nm

sphere 100nm

cylinder

hemisphere

Lambertian

horizontal dipole

Fraction scattered into substrate

Pathlengthenhance

ment

30 x

(A=0.95)

(A=0.90)

Kylie Catchpole



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c-Si c-Si100 m

Integrating

sphere

30 nmSiO2Si3N4TiO2

Optical absorption (1-R-T) in Si wafers

Si3N4

TiO2

SiO2

Si3N4

TiO2

SiO2

Ref.

AR effect, interference

for shorter wavelength+ redshift

Ref.

Strongly enhancednear-IR absorption

egineered bydielectric spacer

Kylie Catchpole, Fiona BeckJ. Appl. Phys. 1 0 5 , 114310 (2009)


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Photocurrent, external quantum efficiency

SiO2front

back

Si3N4

TiO2

SiO2

Si3N4

TiO2

SiO2

front

back

Kylie Catchpole, Fiona BeckJ. Appl. Phys. 1 0 5 , 114310 (2009)


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(a) (b)

(c) (d)

Fabrication of large-area metal nanopatterns

Evaporation and annealing (ANU) Porous alumina template (CALTECH)

Substrate conformal imprint lithography (SCIL) - Philips


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The EconomistJanuary 20, 2009

h b f l


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Amorphous Si thin film solar cell fabrication steps


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Amorphous Si thin-film solar cell fabrication steps

Soft-imprint by Verschuuren et al.Hot-wire a-Si deposition by Schropp et al.

Vivian Ferry, Marc VerschuurenAppl. Phys. Lett. 9 5 , in press (2009)

Ag ont t fte o e o ting imp inted ol gel


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500nm

Ag contact after overcoating imprinted sol-gel

513 nm pitch225 nm diameter240 nm deep

printed over 6 wafer


f ll f b


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Cross section after cell fabrication

imprint layer 150 nmAg 200 nm

ZnO 100 nm

n-a-Si:H 20 nm

ITO (AR coating + topcontact) 80 nm

i-a-Si:H 500 nm

p-a-Si:H 20 nm

1 m


Current Voltage measurements


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Current-Voltage measurements


Measured spectral response


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Measured spectral response

51% increase inphotocurrent from

600 800 nm

no decrease inperformance from

400-600 nm


Comparing with full-field EM simulations


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Comparing with full-field EM simulations

Calculation of lightabsorption usingfinite-difference

time-domainsimulation

Carrier collection

assumed depthindependent


Larger improvement possible with other patterns


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Larger improvement possible with other patterns

Optimum:

depth = 140 nm diameter = 370 nm enhancement = 54%

CalculatedphotocurrentEnhancement

(=600 nm)




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Other plasmonic solar cell designs


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Other plasmonic solar cell designs

Ewold VerhagenOptics Express 1 7 , 14586 (2009)


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Needed: 3 Ph.D. students / post-docs

For details/referencesvisit: www.erbium.nl

6 albert polman fom-institute amolf amsterdam

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