Synergy - Nano-Tera 2016

8/17/2019 Synergy - Nano-Tera 2016

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C. Ballif, Nano-Tera.ch Meeting 2016

Synergy : Systems for Ultra-high

Performance Photovoltaic Energy

Harvesting

26.04.2016

Christophe Ballif


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Prof. Michael

Graetzel

Prof. Christophe

Ballif

Prof. Anna

Fontcubertai Morral

Dr. Julien Bailat Prof. Ayodhya N. Tiwari

Industrial partners:

2

Dr. Björn

Niesen


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Goal of the project

“Realizing photovoltaic energy harvesting systems based on

tandem solar cells with efficiency beyond that achievable withstate-of-the-art industrial single-junction cells”

3


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C. Ballif, Nano-Tera.ch Meeting 2016 4

Benchmark

• 0.55-0.8 €/W at 17-21 % module

efficiency (95-160 €/m2)

• Electricity at 5 cts/kWh in sunny

countries

Various markets

Photovoltaic

power plants

• Needs higher

efficiency, lower

manufacturingcosts, higher

reliability (> 30

years lifetime)


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Benchmark

• Application specific• Needs best efficiency at

low-medium illumination

level («shunt free

devices»)

Ubiquitous energy

scavengers

• Needs higher

efficiency

• Acceptable

manfacturing costs

• Sufficient reliability

Various markets


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Copyright 2016 CSEM | Jba/CBa| Page 6

Energy scavenger: flexible PV with high performance at

ultra-low illumination

100% manuf. @CSEM

Meas. after encapsulation

Pm = 15 μW/cm2

Vm = 0.5 V

Pm = 1.5 μW/cm2

Vm = 0.44 V


7/37Copyright 2016 CSEM Didier Dominé | Page 7

Autonomy for the internet of things

• Two 9.4 cm2 PV cells

• Jumpers for: series / parallel connection

• 1000 Lux: Voc = 670 mV per cell; Pmpp = 60 μW/cm2 (564 μW)

• 25 Lux: Voc > 520 mV per cell; Pmpp >1 μW/cm2 (>9.4 μW)


8/37Copyright 2016 CSEM Didier Dominé | Page 8

Small series production for powering the internet of things

• Series connection and voltage up

to 1000 V on mm2 possible

• Over 5000 chips produced and

tested in 2016 already


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Perovskite

CdTe

Breaking the barriers

Lab record Efficiencies (worldwide):

Silicon solar cells: 25.6%

CIGS: 22.3%

Close to practical limit: 26-27% for Si

(theoretical 1 sun limit 29.4%)

Source: U. Sydney, updated values added

CIGS

9

Solution….?


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Multi-junction solar cells

Combination of high bandgap top cell

with low bandgap bottom cell

Realistic potential for efficiencies > 30%

Careful choice of absorber materials is

important

Source: pveducation.org

Si


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Tandem cells

Several PV technologycombinations:

• Top cell:

Perovskites or GaAs nanowires

• Bottom cell:CIGS or Silicon cell

Superstrate /encapsulation

Si or CIGS bottom cell

Transparent contact

Perovskite or GaAs NW

top cell

Optical coupling/

interconnection

Transparent contact

Transparent contact

Rear contact

Substrate /

encapsulation

Two tandem configurations:

• Mechanically stacked 4-terminal tandems

• Monolithically integrated 2-

terminal tandems


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Transparent contact

Perovskite or GaAs NW

top cell

Optical coupling/

interconnection

Transparent contact

Transparent contact

Rear contact

Substrate /

encapsulation

12

Top Cell Developement

Challenges:

• Top cell performance

• Electrodes with broadband

transparency• Parasitic absorption in charge

transport layers

• Low-temperature processing

• Stability• Up-scaling to bottom cell size


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Proof of concept III-V on Si


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Top cell: GaAs nanowire arrays

Eg(GaAs) = 1.42 eV

Eg(Si) = 1.1 eV

Fontcuberta et al., Nature Photon. (2013)

Monolithic tandem Mechanically stacked


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ITO

PDMS

ITO

NW

2 m

200 400 600 800 1000 12000.0

0.2

0.4

0.6

0.8

1.0

E Q E

Wavelength, nm

Si solar cell along

with high density NW-PDMS

with low density NW-PDMS

2 m

1 cm

321

1 – 5x10⁷ /cm²

2 – 3x10⁸ /cm²

3 – 5x10⁸ /cm² NW density

Transmittance

NW embedded in the PDMS and peeledfrom the substrate

15

G A i b d ll ith


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GaAs nanowire-based cells with

transparent contact

• GaAs n-i-p cells are made by radial

doping of nanowires and sputtered ITOtransparent front contact

• Proof of concept device with Jsc = 12.5

mA/cm2 and Voc = 0.24 V

2 µm

GaAs NWs ITO

PDMS

p-Si

Al

P+-Si

ITO

PDMS

p-i-n GaAsNW forest

Principal scheme of device

Ti/Au

16


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Validation of concept with Si bottom


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GaInP/ Silicon heterojunction tandem

Mechanically stacked 4-terminal GaInP /

Si heterojunction tandem cell

Cell size: 1 cm2

29.8% certified efficiency

WR for Si-based tandem!S. Essig et al. To be

published in IEEE JPV But expensive top cell….


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Top cell: Perovskite solar cell

Variable bandgap 1.5 -

2.3 eV

Most commonly used

material: MAPbI3 with Eg=

1.56 eV Efficiency > 21%

Potential for low-cost

processing

A = large cation (CH3NH3, Cs)

B = small cation (Pb, Sn)X = halogen (I, Cl, Br)

Green et al., Nature Photon. (2014)

Substrate (Glass, PET Foil, etc.)

Transparent front electrode

Transport layer (p oder n)

Perovskite

Transport layer (n oder p)

Single-junction: metal electrode

Tandems: Transparent electrode

A new class of «direct

bandgap» semiconductor


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High efficiency single junction


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Stability and performance: Novel PK materials

M. Saliba et al.,Energy Env. Sci. 2016

• Small fraction of Cs included into perovskite absorber• Record efficiency of 21.1% measured at MPP

• Enhanced stability compared to standard perovskite

materials

21

Lo temperat re pero skite process


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Low temperature perovskite process:

solution-based recipe

0.0 0.2 0.4 0.6 0.8 1.0 1.2

-25

-20

-15

-10

-5

0

Voltage / V

J sc/mAcm-2

SnO2

TiO2

At 10 mV/s

X

X

i

SnO2

FTO

Perovskite

HTL

Au

Scan

directio

n

Jsc(mA cm-2)

Voc(V)

FFPCE

(%)

Light

intensity

(mW cm-2)

SnO2backward 21.3 1.14 0.74 18.4

98.4forward 21.2 1.13 0.75 18.1

TiO2 SnO2

X

Perovskite Perovskite

ESL

FTO

Perovskite

HTL

Au

Highly efficient planar perovskite solar cells through band alignment engineering

DOI: 10.1039/C5EE02608C (Communication) Energy Environ. Sci., 2015, 8, 2928

L t t kit

http://dx.doi.org/10.1039/C5EE02608Chttp://dx.doi.org/10.1039/1754-5706/2008http://dx.doi.org/10.1039/1754-5706/2008http://dx.doi.org/10.1039/C5EE02608C


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• Pin-hole free perovskite layer

• Flat and homogeneous over

5x5cm2 substrates

• Controllable thickness and

composition

• High sub-bandgap transmittance

Low temperature perovskite process:

hybrid vacuum/solution-processing


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Semitransparent planar perovskite solar cell with 16% efficiency

Maximum power point tracking for > 8 minutes

Negligible hysteresis

Perovskite cell with transparent contacts (2)

Hybridevaporation/

solution-

processing

process,(


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Perovskite mini-module

~100 cm2

~10 cm2

~0.2 cm2

Standard

lab cell size

Challenges:1) Obtain uniform perovskite layer over full substrate size

2) Eliminate pinholes in perovskite and transport layers

Mini-modulesize

Typical 4-inch

wafer size


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Perovskite mini-module: Approach

Soo-Jin Moon et al. IEEE JPV, 2015

Unpublished

Uniform perovskite layer by optimized

spin-coating process

Laser scribing to define and

interconnect segments

• Module with active area

efficiency of 12.6%

• Aperture area efficieny of 11.5%


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Bottom cell development

Cu(In,Ga)Se2 and silicon

heterojunction bottom cells

• Optimization of CIGS absorbermaterial for tandem cells

• Highly transparent electrodes

(ITO, IZO, ZnO:B, …)

• Rear reflector, to boost infraredquantum efficiency



Transparent contact

Perovskite top cell

Optical coupling/

interconnection

Transparent contact

Transparent contact

Rear contact

Substrate /

encapsulation


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Exemple: bottom cell: Cu(In,Ga)Se2

Efficiencies > 20% with low band gap materials and high

spectral response in the high wavelength region

ideal as bottom cell

High SR

suitable as

bottom cell

A. Chirila et al., Nature Materials 10, 857 (2011) A. Chirila, P. Reinhard et al., Nature Materials 12, 1107 (2013)

20.4%

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Si heterojunction cells with amorphous IZO

Superior performance

compared to standard

ITO electrode

M. Morales-Masis, et al.IEEE J. Photovoltaics 5 (2015).

• Baseline process for 21-22% devices

• With 22.5% certified

Mechanically stacked 4 Terminal


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Mechanically stacked 4-Terminal

tandems

• Both sub-cells processed

independently

• Offers large freedom fortemperature budget, cell

orientation and surface texture

• 3 transparent electrodes needed,

resulting in increased parasiticabsorption

Superstrate /

encapsulation


Transparent contact

Perovskite top cell

Optical coupling/

interconnection

Transparent contact

Transparent contact

Rear contact

Substrate /

encapsulation

4 terminal Perovskite/CIGS tandem solar cell


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4-terminal Perovskite/CIGS tandem solar cell

20.5% efficiency

Voc (mV) Jsc (mA/cm2) FF (%) h (%)

Perovskite top cell 1104 17.4 73.6 14.2

CIGS cell (stand-alone) 699 34.1 76.7 18.3

CIGS bottom cell 667 12.7 74.9 6.3

4-terminal tandem cell 20.5

Fu et al., Nat. Commun. 6, 8932 (2015)

With low-temperature perovskite cell:

perovskite/CIGS tandem efficiency record!

Perovskite/silicon heterojunction 4 terminal


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Perovskite/silicon heterojunction 4-terminal

tandem measurements

With optical coupling liquid between sub-cells and antireflection foil on perovskite glass substrate

Aperture area:

PSC cell: 0.25 cm2

SHJ cell: 4 cm2

Voc Jsc FF Eff.

PSC reverse 1050 19.8 75.6 15.76

PSC forward 1044 19.7 77.2 15.98PSC Mpp tracking 16.05

SHJ 724 38.3 78.3 21.73

SHJ filtered 701 16.4 78.2 8.96

4-terminal tandem measurement efficiency (stab. Meas.) 25.01

unpublished

From mechanically stacked to


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From mechanically stacked to

monolithically integrated

33MRS spring - EE3.4.2 - [email protected]

4TT

Change top

cell orientation

Double-side

polishedbottom

Replace glass

substrate bysilicon cell 2TT

Single- junction perovskite process flow ≈ Perovskite top cell in monolithic tandem process flow

n

p

p

n

Glass substrate

n

p

p

n

Glass substrate

n

p

p

n

Glass substrate

n

p

p

n

Recombination layer

n

p

p

n

Recombination layer

Low temperature Perovskite/Silicon


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Low-temperature Perovskite/Silicon

monolithic tandem solar cells

Aper ture

area (cm2)

Voc(mV)

Jsc(mA/cm2)

FF

(%)

Eff.

(%)

MPP

tracking

DSP-SHJ 1.22 704 32.1 74.4 16.8

DSP-SHJ, 53% illu mination 1.22 687 17.0 77.1 9.02

Monolithic

tandem

with ARF 1.22 1703 16.1 70.9 19.5 19.2w/o ARF 0.17 1670 13.8 78.6 18.1

with ARF 0.17 1692 15.8 79.9 21.4 21.2

J.Werner et al.

JPCL 7, 161-166

(2016)

Highest published performance for perovskite/Si

monolithic tandem!


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Summary Tandem Efficiencies

Cells 4TT 2TT Reference

PK/Si 13.4% P. Löper et al. PCCP, 17, 2014 Synergy

PK/Si 17% C. Bailie et al. EES, 2014

PK/Si 13.7% J. Mailoa et al. APL, 106, 2015

PK/Si 21.3% Oxford PV, first announced at HOPV15

PK/Si 19.6% J. Werner et al. SolMat, 141, 2015 Synergy

PK/Si 18% S. Albrecht et al. EES, 2015PK/Si 21.2% J. Werner et al. JPCL, 7, 2016 Synergy

PK/Si 19.8% D. McMeekin et al. Science, 351, 2016

PK/Si 20.1% Duong et al. IEEE JPV, 2016

PK/Si 25.0% J. Werner et al. Announced at Spring MRS 2016 Synergy

PK/CIGS 18.6% C. Bailie et al. EES, 2014

PK/CIGS 19.5% L. Kranz et al. JPCL 6, 2676, 2015 Synergy

PK/CIGS 20.5% F. Fu et al. Nat. Commun. 6, 8932, 2016 Synergy


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Summary

GaAs nanowire solar cell with transparent electrodes

High-performance perovskite cells with Cs-based absorber materialwith enhanced stability and efficiency of 21.2%

Fully laser-scribed 5 cm x 5 cm perovskite mini-module

4-terminal perovskite/CIGS and perovskite/Si tandem cell

measurements with performance up to 25%

Monolithic perovskite/Si tandem cell with >21% efficiency

Promising steps towards optimized tandem devices, with potential

efficiencies beyond 30% Exploring commercialization paths with industry partners


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C Ballif Nano Tera ch Meeting 2016

Thank you for your attention!

Thanks to all co-workers at EPFL LPI,

PV-lab , LMSC at EMPA and CSEM andto industry partners for providing

technical and hardware support !

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Synergy - Nano-Tera 2016