[PPT] - University of Milano-Bicocca Simona Binetti S.Binetti, Sydney 27th PowerPoint Presentation

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Simona Binetti Earth-abundant chalcogenide thin film for PV application: the activity of MIB-SOLAR center at University of Milano-Bicocca

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S.Binetti, Sydney 27th November 2019

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The University of Milano-Bicocca

www.unimib.it

S.Binetti, Sydney 27th November 2019

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Economics & Statistics Law Education Sociology Medicine Psychology Sciences Founded in 1998 14 Departments + 2 Schools

37,197 students The University of Milano- Bicocca

S.Binetti, Sydney 27th November 2019

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Our Figures & Numbers

981 Faculty Members 721 Employees

1

Doctoral School with

19

PhD courses

70 total Degree

Courses

13

International Summer School Programs

28 Specialization Degrees

6 Master Degrees +12 POSTGRADUATE Programs (1 year) entirely thought in English 11 double degrees

S.Binetti, Sydney 27th November 2019

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8 Dep.ts are benchmark of EXCELLENCE 2nd in The

National ANVUR

ranking on Big Universities # 3 in Lombardy for

number of students

What we achieved in 20 years

S.Binetti, Sydney 27th November 2019

Rank N. 82

Among universities less than 50 years’ old

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U11 U3 U4 U17 U7 U6 U12 U1 U2 U5 U9 U14 U16

Campus MILANO

S.Binetti, Sydney 27th November 2019

Bicocca Stadium

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Campus Maldives

Marine Research and High Education Center (#MaRHE Center)

U96

S.Binetti, Sydney 27th November 2019

http://www.marhe.unimib.it/

environmental sciences , marine biology, science of tourism , human geography

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Department of Material Science www.mater.unimib.it

S.Binetti, Sydney 27th November 2019

Bachelor and Master Degrees:

Materials Science
Chemistry
Optical Technologies
Phd in Materials Science

In a competitive funding from the Italian Government the SdM was granted to the best 180 Italian Departments : The project “Electrical Power and Energy Vectors from Renewable Sources “ FLEXILAB; research activity on materials for a sustainable energy cycle.

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9

fully equipped synthesis and characterization labs

FABRICATION OF CELLS AND MODULES 100 m2 ISO 7 clean room To support SME companies: from Research to Market Base Research

Mission PV center allowing to pass from an academic research to the setup of a prototype devices

MIB-SOLAR CENTER @ UNIVERSITY OF MILANO BICOCCA

Founded in 2010

FULL MEMBER OF

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MIB-SOLAR equipment

Material Characterization Raman spectroscopy FT-IR, FT-NIR HR Scanning Electron Microscopy (EBIC) X-ray Diffraction Photoluminescence spectroscopy UV-Vis/NIR spectroscopy Hall measurements Material and cell preparation CIGS, CZTS and DDSC cells and mini-module innovative growth process for CIGS sputtering system glove box laser scribing machine Hotplates, furnaces screen printers UV-ozone cleaners Devices Characterization solar simulators up to 6 x 6 inches I/V characterization Internal and external quantum efficiency light soaking chamber for cell ageing stability studies electrochemical impedance spectrometer

S.Binetti, Sydney 27th November 2019

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11

Inorganic Photovoltaic devices

Silicon
Inorganic thin film (CIGS – CZTS)

Solar fuels (artificial photosynthesis)

Production of Hydrogen

Purification of Biogas Organic Photovoltaic devices

Dye sensitized solar cells

MIB-SOLAR RESEARCH TOPICS

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Inorganic Photovoltaic materials and devices

Silicon solar cells Since 1991 involved in EU project on silicon solar cells mc –Si: role of defects (dislocations, grain boundaries) Metallurgical silicon : defect and compensation effect Light harvesting, (EVA doped with Eu complexes) Inorganic thin-film technologies: growth and characterization

Cu(In,Ga)Se2
CZTS
CMTS

III-V based multijunction solar cells : characterization

AlInGaP and AlInGaAs for 4 junction devices

for space application (CESI Spa) (h=34%)

Integration of triple junction on silicon

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S.Binetti

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Chalcogenide thin film solar cells

✓Cu(In,Ga)Se2 (CIGS) solar cells are very well

positioned in the PV technologies with present record efficiencies 22.9 % for small cells and 16.5 % for production size modules

(Total world-wide CIGS production capacity is ~2 GWp/a)

✓Diversification of production and design of CIGS modules

CIGS glass-glass products for BIPV
Flexible and light weight CIGS modules

for PIPV ✓CIGS can be used as bottom cell in tandem devices (h> 30 %) ✓Lower temperature coefficients, higher shading tolerance , a good low light performance are also key CIGS properties, plus a short energy payback time

image: Manz AG

http://cigs-pv.net/white-paper-for-cigs-thin-film-solar-cell-technology/

S.Binetti, Sydney 27th November 2019

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CIGS technology: open questions

Complexity of the absorber layer (significant challenges for uniform film

properties across a large area)

the knowledge of the absorber layer is not sufficient
Current production should increase
So far being able to produce solar panels at prices that can compete with

polycrystalline or cadmium telluride panels has not been possible.

New deposition system for an easy scale up roll-to-roll configuration (for flexible

substrate) is necessary Most CIGS solar cells are nowadays produced using a co-evaporation technique that involves vacuums and can be costly and time-consuming.

S.Binetti, Sydney 27th November 2019

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Cu(In,Ga) Se2 @ MIB-SOLAR: A new hybrid sputtering /evaporation process

1. The metal precursors are

sputtered on rotating transfer devices

2. Then the metals are

evaporated on the substrate by local heating elements in a Se atmosphere

3. The sputtering and the

evaporation processes continue up to the desired thickness is reached

4. Cooling steps in the

presence of Se

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“ transfer devices made by graphite stripes”

M.Acciarri & S. Binetti et al. Solar Energy , 175, 16-24 (2018) S.Binetti et al Semicond. Sci . Technol. 30 (2015) 105006

J. Parravicini, et al. Applied Spectroscopy 71(6), 1334-1339 (2017)
J. Parravicini et al. Applied Optics, 57 (8), 1849 (2018)

S.Binetti, Sydney 27th November 2019

PCT European Appl., EP 13425019

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Deposition time is 30 min (CIGS layer ≈2 mm )
Deposition Process T = 550 °C (or 450 °C )
Substrates: maximum size 20 cm x 120 cm in a roll-to-roll configuration
R&D line that gets the cell and their characterization within less 24 h from

deposition

We define the cell size by mechanical scribing cell area equals 0.50 cm2

Basic steps of CIGS solar cell process @ MIB-SOLAR

500nm AZO window layer substrate 1μm Mo back contact 2~3μm CIGS absorber layer 50nm CdS buffer layer (ZnS) 50nm i-ZnO buffer layer 3μm Ni/Al grid

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S.Binetti, Sydney 27th November 2019

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CIGS Best results

Glass flexible steel foil (120 mm)

h [%]: 13.6

Voc [mV]: 540.6 FF [%] 70.65 Jsc [mA/cm^2]: 31.18 Area [cm^2]: 0.48 h [%]:

15 %

Voc [mV]: 581.7 FF [%] 72 Jsc [mA/cm^2]: 34.52 Area [cm^2]: 0.48

T= 550 °C

Voc= 528 mV Jsc= 35.84 mA cm-

2

FF= 64.4 %

h= 11.7 %

Without antireflection coating

Polyimide T =450°C Flexible Thin glass (125 mm)

Voc= 491 mV Jsc= 38 mA cm-2 FF= 67 %

h= 12.5 %

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CuGaS2

Eg= 2.4 eV for tandem solar cells

S.Binetti, Tallin 25th June2019

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A new method based on repeated bromine etching of CIGS thin film and the measure of the A1 mode Raman shifts

5 10 15 20 25 30 35 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Flux (arb. unit) Time (min) Ga In Cu

100 200 300 400

Temperature (°C)

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300

200 700 1,200

Ga/(Ga+In)

149 155 157 Tiwari

Applied Spectroscopy 71(6), 1334-1339 (2017)

by SIMS

A suitable [Ga]/([Ga]+[In]) (GGI) in-depth profile has proved to play a key role in the performance of cells.

S.Binetti, Sydney 27th November 2019

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CIGS deposition system in production line

This process has been transferred in a 1 MW production line

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http://sunplugged.at/

S.Binetti, Sydney 27th November 2019

1 mm/sec substrate velocity

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Critical Metals in Inorganic thin film PV Technologies

✓The current indium extraction rate permit to estimate a global CIGS solar module production less than 100 GWp ✓Due to the adverse effects on the environment and human health, the supply and use of cadmium is restricted in Europe under the REACH regulation ✓High price

To raise the competitiveness of thin films based modules, rare and toxic elements should be avoided in all layers of the solar devices. Abundance in Earth's Crust of the elements Cu 0.0068 % Zn 0.0078 Sn 0.00022 % Ga= 0.0019% Se= 5x 10-6% In = 0.00016% Ga = 19 ppm In= 0.25 ppm Se = 0.05 ppm

Strong constraints impose to investigate new materials

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S.Binetti, Sydney 27th November 2019 A.Le Donne, V. Trifiletti & S. Binetti “New Earth-Abundant Thin Film Solar Cells Based on Chalcogenides” Frontier in Chemistry 2019 doi: 10.3389/fchem.2019.00297

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Kesterite: Cu2ZnSnS4

➢ Kesterite structure ➢ (CZTS) Enviromentally friendly , low cost ➢ Intrinsic p-type conductivity (CuZn antisite – VCu) ➢ Egcanbe tuned between 1.45 and 1.65 eV (DIRECT) or 0.95-1.05eV ➢ High absorption coefficient (> 104 cm-1) ➢ Efficiency record ηrecord= 11% * (CZTS) - 12.6% (CZTSSe)

Cu Sn Zn S

S.Binetti, Sydney 27th November 2019

*C.Yan et al. Nature Energy 2019, 3- 764

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1 . Metal Precursos

sputtering RF from Cu, Zn, Sn (5N) target on

5x2 cm2 Mo coated SLG

2 . Sulphurization process

0.5 – 0.2 g of S in graphite crucible@250 °C in Ar flow = 30-40 cm3/min - T= 550 °C for 60’

Cu2ZnSnS4 by sputtering

S. Marchionna, P. Garattini, A. Le Donne, M. Acciarri, S. Tombolato & S. Binetti Thin Solid Films 542, 114 (2013)
A. Le Donne S. Marchionna, P. Garattini, R.A. Mereu, M. Acciarri & S. Binetti International J.of Photonergy (2015)

450 °C SOLAR

S.Binetti, Sydney 27th November 2019

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η [%]: 3,95 Voc (mV) 531 FF [%] 44,8 Jsc (mA/cm2) 16,6

Active area = 0.15 cm2

0,4
0,2

0,2 0,4 0,6

20
15
10
5

5 10

V (V) J (mA/cm

2)

CZTS by sputtering results

300 400 500 600 700 800 900 1000 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 0.0 0.1 0.2 0.3 0.4 0.5

EQE

2

E (eV)

Zn-rich CZTS cell (this work) CZTS record cell (Shin et al.)

EQE

wavelength (nm)

Egap = 1.5 eV

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S.Binetti, Sydney 27th November 2019

S. Marchionna, et al. & S. Binetti Thin Solid Films 542, 114 (2013)

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CZTS sputtering samples: Material Properties

200 250 300 350 400 450 500 1,5 2,0 2,5 3,0 3,5

267

287 290 308 377

368

355

Raman shift (cm

1)

Intensity (arb. units)

338

Along with the CZTS characteristic modes at 267, 287, 338 and 368 cm-1, the Raman spectrum shows additional contributions at 290, 355 and 377 cm-1, typical of cubic CTS

20 30 40 50 60

50 100 150 200 250 300 350

I (arb. units)

2

CZTS

Mo

(112)

(220) (312) (200)

Kesterite Structure EDX : The mean atomic concentration of Cu, Zn, Sn and S resulted 15%, 16%, 10% and 47%,

Cu/Zn+Sn = 0.5 Zn/Sn = 2.3

Eventually ZnS spurious phases were removed by etching in HCl (aqueous solution 5% at 75 °C for 300 sec).

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S.Binetti, Sydney 27th November 2019

SLIDE 25

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A. Le Donne, S. Marchionna, P. Garattini, R.A. Mereu, M. Acciarri and S. Binetti " J. of Photonergy Volume 2015,

Article ID 583058

CZTS defect identification by PL

S.Binetti, Sydney 27th November 2019

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Molecular inks :

Aim: Develop a simple , cheap , no toxic process based on the sol-gel technique

CZTSsol was prepared by dissolving in DMSO:

Cu(CH3COO)2·H2O;
SnCl2·2H2O;
Zn(CH3COO)2·2H2O.

After complete dissolution, thiourea was added.

We investigated the composition and stability of the molecular ink

V. Trifiletti et al., Chemistry Select 2019, 4, (17), 4905-4912.

High quality CZTS thin films by wet process

S.Binetti, Sydney 27th November 2019

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Sol-gel evolution

600 650 700 750 800

731 723 705 672

Intensity (a.u.) Raman shift (cm-1) film after 6 h film after 30 h

730

Ink composition : Cu(CH3COO)∙H2O Zn(CH3COO)∙2H2O SnCl2∙2H2O in (DMSO and TU)

48 96 144 192

20 40 60 80 100

n (mm2 s-1) Time (h)

Viscosity

300 K

200 400 600 800 1000 1200 1400

0,0 0,2 0,4 0,6 0,8 1,0

Normalised Intensity (a.u.)

Raman shift (cm-1)

DMSO INK

730

TU

The Sol-gel viscosity increases due to polycondensation process, until the ink evolves to gel After drying in air the DMSO signal disappears, and after 30 hours the thiourea signal splits in bands that are assigned to the metals coordinate by TU.

S.Binetti, Sydney 27th November 2019

V. Trifiletti et al., Chemistry Select 2019, 4, (17), 4905

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Zn(CH3COO)2 ∙ 2H2O Cu(CH3COO)2 ∙ H2O SnCl2 ∙ 2H2O

Solvent: DMSO 3.0 mL

Thin films were fabricated by 1) a direct drop-casting

f the solution

2) Gelation in 30’ at RT after droplet deposition

Thiourea

3) 1st and 2nd Layer: Oven annealing in Argon @ 550 °C

1st Layer: 4 μL/cm2 2nd Layer: 6 μL /cm2 0.8 mmol 0.5 mmol 0.5 mmol 9.0 mmol

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S.Binetti, Sydney 27th November 2019

loading final thickness: 1.2 -1.5 μm

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Optimization of the solution/film

S.Binetti, Sydney 27th November 2019

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SLIDE 30

2θ = 16.5, 18.4, 23.3, 28.7, 33.2, 47.5

S.Binetti, Sydney 27th November 2019

20 25 30 35 40 45 50 55

200 400 600 800 1000 1200 1400 1600 1800 2000

Intensity (arb) 2θ (deg)

XRD Raman Spectra

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CZTS drop casting samples: material properties

Unpublished results

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XPS analysis on CZTS film

Cu, Zn, Sn, and S oxidation states: Cu (I), Zn (II), Sn (IV) and S (II)

From Ms. Sally Luong, Dr Vanira Trifiletti and Dr Oliver Fenwick School of Engineering and Materials Science ,Queen Mary University of London S.Binetti, Sydney 27th November 2019

Ion Beam Etch: 30 sec x 3 times (30 nm each time ) Energy 8000 eV Raster size 1 mm Cluster size 1000

Sample #2

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Unpublished results

SLIDE 32

Band gap and PL

S.Binetti, Sydney 27th November 2019

0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 0,0 0,2 0,4 0,6 0,8 1,0

E (eV) PL intensity (arb.units)

Quasi Donor-Acceptor Pair (QDAP) recombination

T= 13 K lexc= 805 nm InGaAs detector Dl= 6.6 nm

P= 18W/cm2 P= 0.17 W/cm2

0,9 1,2 1,5 1,8 2,1

0,00E+000 1,00E+009 2,00E+009 3,00E+009 4,00E+009 5,00E+009 6,00E+009

Equation y = a + b*x Plot alfa2xeV Weight No Weighting Intercept

1,14593E10 ± 1,19657E7

Slope 7,95113E9 ± 7217051,23592 Residual Sum of Squares 1,92277E15 Pearson's r 0,99996 R-Square (COD) 0,99992

Adj. R-Square

0,99992

Eg = 1.44 eV

(ahu)2 (eV cm-1)2

Energy (eV)

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Unpublished results

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Device Performance

Voc = 175.0 mV Jsc = 18.93 mA/cm2 η = 1.11 % FF = 33.43 %

Modest Voc Respectable Jsc

SCAPS software simulation indicates problems at the interface with the back contact

S.Binetti, Sydney 27th November 2019

400 600 800 1000 0,0 0,2 0,4 0,6 0,8

EQE Wavelength (nm)

0,3
0,1

0,1 0,3 0,5

0,03
0,01

0,01 0,03 0,05 0,07 0,09 Dark Illuminated

Current Density (A/cm2) Tension (V)

Voc = 175.0 mV Jsc = 18.93 mA/cm2 η = 1.11 % FF = 33.43 %

Surf. area = 0.15 cm2

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Unpublished results

SLIDE 34

Kesterite thin films by non toxic solution process

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Thermal treatment without sulfurization Dimethylsulfoxide Thiourea Metal salts Spin Coating on substrates

n FTO or Mo Glass)

Precursor-ink Cu2ZnSnS4 Thin-film

Spreading on FTO Glass or Mo coated glass 550°C in Argon , no S

Dimethylsulfoxide (DMSO)

Precursor Ink

Gelation process Thiourea (TU)

Metal salts

Thin film 1 2

V. Trifiletti et al., Chemistry Select, 2019

S.Binetti, Sydney 27th November 2019

Several deposition methods + a ink jet printer (in progress) Precursor-ink 3

SLIDE 35

Molecular inks : CZFTS sol was prepared by dissolving in DMSO:

Cu(CH3COO)2·H2O;
SnCl2·2H2O;
Zn(CH3COO)2·2H2O.
Fe(CH3COO)2

After complete dissolution, thiourea was added.

S.Binetti, Sydney 27th November 2019

Tuning the gap Cu2Zn1-xFexSnS4

Ink is spread on Mo SLG and HT @550 °C in S Preliminary thin film results very promising

SLIDE 36

CZTS by wet process : summary

In the precursor-ink:

✓

TU acts as a monodentate ligand for the metal ions and DMSO solvates them;

✓

DMSO supports TU coordination. Kesterite phase formation in the final film is supported by:

➢

the acetate groups, which bridge the different metal ions, creating a network, and favour the sol-gel formation;

➢

the homogeneous distribution of the components.

➢

Promising material quality and Isc Open questions Low efficiency (problem with back contact (MoS2 ? ), no etching with KCN, intermediate passivation layer , alternative buffer layers…

Thermal treatment without sulfurization

DMSO TU Metal salts Deposited on Mo/SLG Precursor-ink Cu2ZnSnS4 Thin-film

S.Binetti, Sydney 27th November 2019

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SLIDE 37

Advantages :

Fast steps
Control on stoichiometry (layer thickness)
Scalable to large surfaces
Constrained stacking order
Lower quality than vacuum processes

Anhydrous ethylene glycol ; copper acetate 0.05 M ; sodium acetate 1 M ; diethanolamine 0.8 M; dimethylamine borane complex 0.1 g/L Zn/Sn =1.1 Cu/Zn+Sn = 0.85

Cu Sn Mo/SLG Zn

CZTS by electrodeposition

non-aqueous plating solution:

G. Panzeri et al. Electrochemistry Communications 109 (2019)

stack elemental layers approach of CZT precursors + sulfurization

is one of the most attractive fabrication routes: large area and low-cost process and easily scalable

SLIDE 38

I

M.I. Khalil, et al . Applied Surface Science 379, 91–97 (2016) M.I.Khalil, et al .“Co-electrodeposition of metallic precursors for the fabrication of CZTSe thin films solar cells on flexible Mo foil" Journal of The Electrochemical Society, 164 (6) D302-D306 (2017)

CZTSe by electrodeposition

Co-electrodeposited Cu-Zn-Sn precursor + sulfurization or selenization on Mo flexible foil which acts both as a substrate for the electrodeposition process and as a back contact

0.1% with Jsc= 3.9 mA/cm2 , Voc= 119 mV in our first attempt.

S.Binetti, Sydney 27th November 2019

SLIDE 39

A new alternative:

– p-type semiconductor fully based on Earth-abundant and low-cost elements : – the abundance in the Earth’s crust of Mn is two order of magnitude higher than that of Zn (1100 ppm vs 79 ppm)*, – is definitely cheaper (the amount of Zn produced in 2015 was 4’600’000 tons lower than that of Mn (13’400’000 Zn tons vs 18’000’000 Mn tons). – Lower Wp cost – Up to last year studied as Diluite Magnetic Semiconductor

Cu2MnSnS4

ALTERNATIVES TO CZTS:

Cu2M(II)M(IV)S4

with M(II) = Zn, Mn, Fe, Ni, and M(IV)= Si, Ge, Sn

S.Binetti, Sydney 27th November 2019

*A. Le Donne, V. Trifiletti , & S.Binetti * Frontier in Chemistry 2019

SLIDE 40

Cu2MnSnS4

Vacuum approach: Metal precursors evaporation followed by annealing in elemental sulfur vapors

Metal Precursors: 4-sources EB evaporation system + Sulfurization

Testing :
the thickness and order of the metal precursors in the evaporated stack
Annealing temperature : 500°C, 525°C, 555°C, 585°C, for 1 h (ramping rate:15°C/min)
Pre-annealing to enhance metal intermixing(115°C for 1 h).

Substrates: soda lime glasses coated with sputtered Mo 1 µm Deposition rate: [Sn] = 0.25 nm/s, [Cu] = 0.12 nm/s, [Mn] = 0.3 nm/s

S.Binetti, Sydney 27th November 2019

SLIDE 41

Cu2MnSnS4 thin film: main properties

✓EDX and Raman analyses confirm that the CMTS phase was obtained ✓Lower content of insulating MnS secondary in the case of lower Mn layer thickness (i.e. 135 nm)

200 400 600 0,4 0,6 0,8 1,0 1,2 1,4 164 (SnS) 350 (CMTS) 282 (CMTS)

Raman intensity (arb. units) Raman shift (cm

1)

655 (MnS) 250 (CMTS) 300 (CMTS) 364 (CMTS) 330 (CMTS)

✓Stannite Structure

(+ sulfide compound with spinel structure)

S.Binetti, Sydney 27th November 2019

ID09A beamline at ESFR Synchroton

S. Marchionna et al . J.of Alloys and Compounds 693

(2017) 95

SLIDE 42

Cu2MnSnS4

✓ high absorption coefficient (5x104 cm-1) and direct band (1.26 eV) suitable for PV applications have been obtained

S.Binetti, Sydney 27th November 2019

SLIDE 43

Cu2MnSnS4: solar cell prototypes

CMTS solar cells area = 0.15 cm2

✓ Deep recombination center responsible for the emission at 0.8 eV is associated to a bulk defect. ✓Secondary phases (sulfurization ramping rates to be reduced)

0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 0.0 1.0x10

4

2.0x10

4

3.0x10

4

4.0x10

4

5.0x10

4

shallow level emission lexc= 532 nm lexc= 805 nm

E (eV) PL I (arb. units)

deep level emission S.Binetti, Sydney 27th November 2019

0.4 -0.3 -0.2 -0.1

0.1 0.2 0.3 0.4 0.5

10
8
6
4
2

2 4 6 8 10 h: 0.5% Voc: 302 mV Jsc: 4.6 mA/cm

2

FF: 36%

J (mA/cm

2)

V ( V)

Mn powders**

SLIDE 44

Effect of low temperature annealing on PV performance

✓ annealing at 225°C allows for an improvement of all the device parameters, to 0.83% efficiency

400 500 600 700 800 900 1000 1100 0.00 0.05 0.10 0.15 0.20 0.25 0.30

AG TT 200°C 40' TT 225°C 40' TT 250°C 40' TT 275°C 40'

EQE wavelenght (nm)

0,4 -0,2

0,2 0,4 0,6 0,8

20

20 40 60

No TT h: 0.5% Voc: 297 mV Jsc: 4.5 mA/cm

2

FF: 36% TT 225°C 40' air h: 0.83% Voc: 354 mV Jsc: 5.8 mA/cm

2

FF: 40%

J (mA/cm

2)

V (V)

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It is the present record as Chen et al. (2015) reported 0.49% maximum efficiency on CMTS layers prepared by direct liquid coating

EQE analyses which show a significant increase of the spectral response between 550 and 800 nm for all the tested temperatures, indicating a reduction of recombination losses. But a gradual decrease of EQE in 350 -550 range

SLIDE 45

✓ low-temperature annealing generally reduces the density of the deep bulk defect responsible for the emission at 0.8 eV, thus reducing recombination losses. ✓ before any annealing, CdS shows a very weak PL emission at about 2.5 eV, (nc-CdS) ; After 200 C annealing the PL signal increases and shifts to 2.45 eV indicating an improvement of CdS crystalline quality, and reducing the Eg value (i.e. 2.25 eV).

0.8 0.9 1.0 1.1 1.2 1.3 1.4 0.0 1.0x10

3

2.0x10

3

3.0x10

3

4.0x10

3

5.0x10

3

no TT TT 200°C 40' TT 225°C 40' TT 250°C 40' TT 275°C 40'

E (eV) PL I (arb. units)

2.1 2.2 2.3 2.4 2.5 2.6 2.7 0.0 5.0x10

4

1.0x10

5

1.5x10

5

2.0x10

5

2.5x10

5

3.0x10

5

3.5x10

5

4.0x10

5

no TTx2 TT 200°C 40' TT 225°C 40' TT 250°C 40' TT 275°C 40'

PL I (arb. units) E (eV)

Effect of low temperature annealing on bulk properties

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A. Le Donne, et al. Solar Energy 149 (2017) 125–131, 3283

S.Binetti, Sydney 27th November 2019

SLIDE 46

Conclusion and Future works

To be done : ➢ Reducing harmful defects in CZTS and CMTS ➢ Testing alternative Buffer layer to replace CdS by ALD (i.e. Zn1- xSnxOy or

Zn(O,Se)

➢ CMTS and CFTS by ink approach on flexible substrate

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S.Binetti, Sydney 27th November 2019

Final aim : USE a low cost solution process to get a full inorganic earth abundant based multijunction solar cells

✓ We have developed an innovative way to achieve high-quality kesterite thin-films suitable for PV ✓ CMTS: a new earth abundant material have been tested as PV absorber ✓ CZTS by electrochemical approach is under investigation

SLIDE 47

Thank you for your attention !

simona.binetti@unimib.it www.mibsolar.mater.unimib.it

J. Parravicini

A.Le Donne

G. Tserbelidis
V. Trifiletti (now in UK)
M. Acciarri
L. Frioni

S.Binetti, Sydney 27th November 2019

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S.Binetti, Sydney 27th November 2019

SLIDE 49

S.Binetti, Sydney November 2019

550 °C 450 °C Simulations performed considering the presence of a defective layer at the interface between CIGS and CdS

CIGS

SLIDE 50

S.Binetti, Sydney November 2019

SLIDE 51

Raman spectroscopy in CIGS

The main Raman mode A1 (vibration of the Se anions in the x-y plane with the cations at rest)

increases linearly with increasing Ga content (from 174 cm-1 for CIS to 184 cm-1 for CGS): its position can be used to make a quantitative estimation of the mean [Ga]/[Ga]+[In] and its depth gradient – and depends on the relative Cu content

a shoulder at 150–170 cm−1, is attributed to the OVC (ordered vacancy compound) phase
W. Witte et al . Thin Solid Films

517 (2008) 867–869; Park et al., J. of Alloy and Comp. 513 (2012)068

Advanced Characterization Methods for PV 14th January 2016 S.Binetti

51

SLIDE 52

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 100 200 300 400 500 600 700

Intensity(arb) Wavenumber (cm-1) GT58 Mo con bordo azzurro (MoS2) - VS - GT21 Mo dopo aver sgrattato il CZTS

GT58 bordo azzurro

MoS2 on the back conctac

S.Binetti, Sydney November 2019

SLIDE 53

Tuning the gap by Cu2Zn1-xFexSnS4

SOLAR

Working in inert atmosphere Working in air

S.Binetti, Sydney November 2019

Unpublished resuts CZFTS

In agreement with J.Phys Chem 118 14227

SLIDE 54

Gel formation in situ

Cu2(Zn,Fe)SnS4

250 275 300 325 350 375 400 425 450 Intensity (a.u.) Raman shift (cm-1)

Fe/Zn = 1/9 Fe/Zn = 2/8 Fe/Zn = 3/7 Fe/Zn = 4/6 Fe/Zn = 5/5 Fe/Zn = 6/4 Fe/Zn = 7/3 Fe/Zn = 8/2 Fe/Zn = 9/1

338 325

11

S.Binetti, Sydney November 2019

SLIDE 55

Tuning the gap Cu2Zn1-xFexSnS4

Cu2FeSnS4

45 50 55 60

250 500

(3 1 2) (2 2 0)

Intensity (cps) 2 theta (deg)

25 30 35 40 45 50 55 60

250 500 750 1000 1250 1500

(3 1 2) (2 2 0) (2 0 0) (1 1 2) FTO No 0°C treatment 0°C treatment Intensity (cps) 2 theta (deg)

We were able to grown Cu2FeSnS4 thin-films in kesterite structure, adding a treatment at 0°C after spreading the Ink on FTO.

Kesterite Stannite

9

SOLAR

S.Binetti, Sydney November 2019

SLIDE 56

XRD phase analysis:

500 1000 1500 2000 2500 3000 3500 14 19 24 29 34 39 44 49 54 Intensity (cps) 2θ (deg)

CZTS on Mo-SLG + KCl @ 550 °C * * * * * * *

Mo substrate = x CZTS thin film = *

x

CZTS well-defined peaks with no secondary phases.

S.Binetti, Sydney November 2019

SLIDE 57

Gel formation in situ Cu2ZnSnS4

0,8 1,0 1,2 1,4 1,6 1,8

0,0 0,5 1,0 1,5 2,0

(ahn)2 x 1010 (cm-1 eV)2

hn (eV)

200 250 300 350 400 450

267 288 304 339 352 368

Intensity (a.u.) Raman shift (cm-1)

Raman laser 633 nm

20 30 40 50 60

500 1000 1500 2000 2500 3000 3500

(3 1 2) (2 2 0) (2 0 0) (1 1 2) Intensity (cps) 2-theta (deg)

FTO Cu2ZnZnS4

(1 0 0)

8

S.Binetti, Sydney November 2019

SLIDE 58

CZTS by electrodeposition

Co-electrodeposition of Cu-Zn-Sn (CZT) from alkaline solution

n flexible Mo substrate followed by sulfurization

Potassium pyrophosphate (K4P2O7), CuCl2, ZnSO4∙7H2O, EDTA-Na2 and SnCl2∙2H2O in 100 ml of Millipore water h=0.18 %

G. Marchi et al. Electrochemica acta

SLIDE 59

The deposition of the ZTO films was operated both from a ceramic target (75wt% ZnO – 25wt%. SnO2) and from two metal targets (Zn and Sn) to form a metal bi-layer followed by an

xidation

R.A. Mereu, A. Le Donne, S. Trabattoni, M. Acciarri, S. Binetti, Journal of Alloys and Compounds 626, 112-117 (2015)

Zn2SnO4

SOLAR

S.Binetti, Sydney November 2019

SLIDE 60

Cu2MnSnS4: 2nd Series (VS metals sequence and TT @ 115°C)

✓ the additional step at 115°C is mandatory to obtain larger grains, whose size seems to be almost constant for T > 525°C ✓the sandwich stack structure provided the best morphology in terms of compactness and grain size, but also the higher content

f

insulating spinel secondary phase  the standard stack structure provided the best compromise.

Stack structure Sulfurization temperature Cell parameters [Å] from XRD analysis c/a ratio [Stannite]/[S pinel] ratio a b c Standard 150 +525°C 5.503 5.503 10.855 1.972 89.05% Double 5.489 5.489 10.823 1.972 87.96% Sandwich 5.509 5.509 10.841 1.968 69.47% Standard 150 +550°C 5.505 5.505 10.852 1.971 90.40% Double 5.507 5.507 10.848 1.970 86.23% Sandwich 5.511 5.511 10.836 1.966 76.22% Standard 150 +585°C 5.507 5.507 10.847 1.970 90.71% Double 5.509 5.509 10.845 1.968 90.15% Sandwich 5.512 5.512 10.837 1.966 81.90%

S.Binetti, Sydney November 2019

SLIDE 61

S.Binetti, Sydney November 2019

Raman Shift (cm-1) CZTS 266, 288, 338, 368-374 Cu2SnS3 295-303, 355 SnS2 315 SnS 164, 192,218 ZnS 278, 351 Cu2S 264, 475

SLIDE 62

S.Binetti, Sydney November 2019

0.00 500.00 1000.00 1500.00 2000.00 2500.00 14.00 19.00 24.00 29.00 34.00 39.00 44.00 49.00 54.00

Intensity (cps) 2θ (deg)

CZTS on FTO

FTO substrate = x CZTS thin film = *

* * * * *

x x x x

SLIDE 63

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 200 220 240 260 280 300 320 340 360 380 400

Intensity (arb) Wavenumber (cm-1)

Our Thin Film CZTS VS Single crystal CZTS Thin film Single crystal

Well-defined peaks, comparable with single crystal XRD!

Raman spectrum:

S.Binetti, Sydney November 2019

SLIDE 64

20 25 30 35 45 50 55 60 65 500 1000 1500 2000 2500 3000 3500 CZTSe (400/008) CZTSe (312) CZTSe (204) CZTSe (112)

Int (a.u.) 2 (°)

CZTSe electrodeposition sample : preliminary results

Ok phase and stoichiometry ➔ Good homogeneity

SLIDE 65

G. Tseberlidis, V. Trifiletti et al., Manuscript in preparation 2019

Device Performance

Voc = 175.0 mV Jsc = 18.93 mA/cm2 η = 1.11 % FF = 33.43 % Modest Voc Respectable Jsc SCAPS software simulation confirms problems at the interface with the back contact

S.Binetti, Sydney November 2019

0.15 cm2

SLIDE 66

PL results

S.Binetti, Sydney November 2019

SOLAR

Thin film (TF) compared with Single Crystal (SC) kesterite These bands could be related to deep donor-deep acceptor (DD-DA) complex defect

J.Krustoka, T.Raadik, M.Grossberg, V. Trifiletti, S.Binetti, Materials Science in Semiconductor Processing , 80, 52 (2018)

The presence of Zni must be reduced Togliere

SLIDE 67

Entry# Cu/(Sn+Zn) Zn/Sn Thiourea [conc.] Voc (mV) Jsc (mA/cm2) FF % η % 1 1.00 1 3.7 M

2

0.91 1 3.7 M

3

0.86 1 3.0 M

4

0.83 1 3.0 M 83.0 8.0 29.1 0.18 5 0.80 1 3.0 M 70.0 11.6 26.2 0.21 6 0.80 1.1 3.0 M 149.4 12.6 31.0 0.58 7 0.80 1.2 3.0 M 175.0 18.9 33.4 1.11 8 0.80 1.2 2.3 M 60.0 7.6 27.0 0.12

G. Tseberlidis, V. Trifiletti et al., Manuscript in preparation 2019

Optimization of the solution

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