high performance silver polymer pastes for shj cells · cc ikts paste 21.8 % using ir curing...

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HIGH PERFORMANCE SILVER POLYMER PASTES FOR SHJ CELLS S. K örnera, A . W altingerb, U. Partscha, M . Ebersteina aFraunhofer IK TS, W interbergstraße 28, 01277 Dresden bM eyer Burger (Germany) A G, A n der Baumschule 6-8, 09337 Hohenstein-Ernstthal

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OUTLINE

IK TS: Paste Research Service (PRS) and Paste V endor for Niche M arkets (PV N)

SHJ: Low Temperature Pastes

Silver polymer paste

Experimental

Results and discussion

Summary

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OUTLINE




Experimental


Summary

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IKTS Group Thick Film Technology, Photovoltaics: Paste Research Service PRS Paste Development , Manufacturing and Characterizat ion

• Functional phase

• Glass • Additives • Organics

(Binder, solvents…)

Composition

• Rheometry • Shrinkage • Thermal

Analysis • Particle Sizes

Paste Characterization

• Screen/ stencil

• M icro dispensing

• Gravure • Aerosol

Deposition

• Thick Film (min … h)

• Solar contact (sec)

Firing • Electrical • Topography • M icro

structure, phase content

Film Characterization

Funct ional Requi rem ent s

„ Ready f or Product ion“

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Paste Vendor for Niche Markets PVN: example AlN subst rates

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Future of crystalline silicon solar cell

ITRPV roadmap 2015 predicts eff iciencies for SHJ up to 25 % and market share of 10 % in the year 2025

BSF/PERC n-type mono Si

SHJ n-type mono Si

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OUTLINE




Experimental


Summary

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Convent ional pastes for f ront side metallizat ion

800 °C, some seconds Cool down

A g

glass

Si 200 nm Li et al., J. Appl. Physics 110, 074304 (2011)

K ulushich, G., B. Bazer-Bachi, et al. (2012 A pril 03-05). Contact formation on 100 Ω/sq emitter by screen printed silver paste. SiliconPV , Leuven, Belgium.

K .-K . Hong, S.-B. Cho, J.S. Y ou, J.-W . Jeong, S.-M . Bea, J.-Y . Huh; M echanism for the formation of A g crystallites in the A g thick-f ilm contacts of crystalline Si solar cells, Solar Energy M aterials & Solar Cells 93 (2009) 898–90

e.g.

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SHJ cell concept

ITO

emitter: a-Si (p)

passivation: a-Si (i)

base: c-Si (n)

M aximum process temperature ≤ 200°C

silver

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Conductive phase A g

glass crucial for adhesion, reactive contact formation, and interface/f inger conductivty

Conductive phase A g or LM PA

polymer crucial for adhesion and interface/f inger conductivity

Low temperature thick f ilm pastes for solar cell metallizat ion

00:18.80 00:43.80 01:08.80 01:33.80 01:58.800

100

200

300

400

500

600

700

800

900

waf

er t

empe

ratu

re [°

C]

t ime [mm:ss.t t ]

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OUTLINE




Experimental


Summary

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Processing of low temperature pastes

t

T

Thermal (IR or convection; air or nitrogen, 2400 wafers / h, manufactured 2015 by REHM , Germany)

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Low temperature thick f ilm pastes for solar cell metallizat ion

tuning of curable binder: polymer, solvent

40 µm 60 µm 80µm 100 µm conductive phases:

A g mono/polymodal Low M elting Point A lloys (LM PA ) Rsq = 25 mΩ/sq

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Experimental

IK TS paste

commercial paste

storage

fridge 7 °C or RT

f reezer -20 °C screen printing

convection

infrared

characterization

• 10 wafer per paste

• 74 f ingers with 100 µm width

• 5 wafer per kind of heat transfer

• 15 min at 200°C

• GridTouch system

• M easured at M eyer Burger (Germany) A G

• comparison with reference

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OUTLINE




Experimental


Summary

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Elect rical performance

IK TS pastes provide slightly lower Jsc

Optimizing paste rheology will increase Jsc due to optimized f inger narrowing and decreasing shading

36.6

36.8

37.0

37.2

J sc [m

A*c

m²]

commercial IK TS

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36.6

36.8

37.0

37.2

J sc [m

A*c

m²]

0.725

0.730

0.735

0.740

V OC [V

]

commercial IK TS commercial IK TS

IK TS pastes provide slightly lower Jsc

Optimizing paste rheology will increase Jsc due to optimized f inger narrowing and decreasing shading

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Series resistances comparable for both pastes

Infrared curing provides lower series resistances as well as a lower standard deviation

Optimized heat transfer due to coupling of IR radiation

1.35

1.40

1.45

1.50

1.55

1.60

1.65

Rser

[Ohm

*cm

²]

0

5000

10000

15000

20000

Rshu

nt [O

hm*c

m²]


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Eff iciency level higher than 21.5 %

CC commercial paste 22 % using IR curing benef it against convection of 0.25 %

CC IK TS paste 21.8 % using IR curing benef it against convection of 0.1 %

Fill factor constant higher than 80 %

21.00

21.25

21.50

21.75

22.00

22.25

Eta

[%]

0.790

0.795

0.800

0.805

0.810

0.815

0.820

fill

fact

or


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Presence and future of crystalline silicon solar cell

2014 2016 2018 2020 2022 2024 202620.5

21.0

21.5

22.0

22.5

23.0

23.5

24.0

24.5

25.0

25.5

cell

effi

cien

cy [%

]

years

Predicted eff iciencies ITRPV Eff iciency reached today

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Performance forecast

Gen. 01 Gen. 02 Gen. 03

Gen. 01 Gen. 02 Gen. 030

5

10

15

20

25

30

Rsq@

25µm

[mO

hm/s

q.]

Ag composite with LM PA Polymodal A g composite

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Summary

1st generation IK TS paste curable at 200°C for SHJ solar cells is introduced

IR curing leads to better electrical performance of the reference paste as well as the own development, obviously due to improved microstructure formation

Electrical performance on cell level is comparable to industrial standard

Handling, storage and therewith processing of IK TS paste is much more easier than the commercial reference

Further improvement announced with next generations:

low melting point alloys with reduced silver amount

polymodal silver powders for minimal f inger resistances

2014 2016 2018 2020 2022 2024 202620.5

21.0

21.5

22.0

22.5

23.0

23.5

24.0

24.5

25.0

25.5

cell

effi

cien

cy [%

]

years

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Thanks t o t he germ an Federal M in ist ry o f Educat ion and Research (M WT+ #03SF0420)…

…and you f or your at t ent ion!

Further Information:

M arkus Eberstein

+49-351-2553-7518

[email protected] raunhofer.de

Fraunhofer Institut K eramische

Technologien und Systeme

W interbergstraße 28, 01277 Dresden

mailto:[email protected]

high performance silver polymer pastes for shj cells · cc ikts paste 21.8 % using ir curing...

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