synergy - nano-tera 2016
TRANSCRIPT
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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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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
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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)
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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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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
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
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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
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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
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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
Superstrate /encapsulation
Si or CIGS bottom cell
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
Si or CIGS bottom cell
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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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 !