transparent front side contact pastes for high efficiency shj … · 2016-05-14 · conductive...
TRANSCRIPT
© Fraunhofer
transparent front side contact pastes for high efficiency SHJ-solar cells
S. Körner1, A. Waltinger2, M. Eberstein1
1Fraunhofer IKTS; 2Meyer Burger (Germany) AG
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future of crystalline silicon solar cell
ITRPV roadmap 2015 predicts efficiencies for SHJT 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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conventional pastes for front side metallization
800 °C, someseconds Cool down
Ag
glass
Si 200 nm
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SHJ cell concept
ITO
emitter: a-Si (p)
passivation: a-Si (i)
base: c-Si (n)
silver-polymer-composite
maximum process temperature ≤200°C
© Fraunhofer 5 / 18
SHJ cell concept
ITO
emitter: a-Si (p)
passivation: a-Si (i)
base: c-Si (n)
maximum process temperature ≤200°C
silver-polymer-compositeinduce power losses due to shading
Why not us ing transparent, intrins ic conductive Polymers?
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intrinsic conductive polymers
conjugated double bonds forms conjungated π- electron system
oxidation / reduction by doping by halogenides or alkaline metals
generating charges along polymer backbone
for charge equalization immobilisation of large counter ions; e.g. sulfonic acids
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intrinsic conductive polymers
conductivity provided by hopping of electrons or holes
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intrinsic conductive polymers
conductivity provided by hopping of electrons or holes
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Experimental
IKTS paste
• dissolved or dry
• adding solvents and other reagents
• optimizing curing profile
• screen print test structures and characterization
pastepreparation
commercial paste
printingsolar cells
IKTS paste
screen printing
• 10 wafer per paste
• 74 fingers with 100 µm width
curing solar cells
30 min @ 120 °C
10 min @ 200 °C
curing characterization
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transparent front side paste – development and characterization
80 120 160
100
1000
10000
sheet re
sis
tsance [m
Ohm
/sq]
temperature [°C]
solvent A
solvent B
solvent C
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SHJ Solar cells – conventional and organic front side metallization
silver free silver
36.0
36.5
37.0
37.5
38.0
38.5
39.0
39.5
Jsc [m
A/c
m²]
silver free silver
0.725
0.730
0.735
0.740
Vo
c [V
]
transparent pastes provides
Higher Jsc than silver paste gain of 1.05 mA/cm²
Higher Voc gain of 4 mV
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SHJ Solar cells – conventional and organic front side metallization
silver free silver
36.0
36.5
37.0
37.5
38.0
38.5
39.0
39.5
Jsc [m
A/c
m²]
gain of Jsc due to transparent paste
Cells without pastes Jsc = 39.4 mA/cm²
6.4 % shading of silver paste leads to decrease down to Jsc = 37.2 mA/cm²
Transparent paste reduces shading down to 1.5 %
no paste transparent silver
35
36
37
38
39
40
Jsc [
mA
*cm
²]
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SHJ Solar cells – conventional and organic front side metallization
silver free silver
0.8
1.0
1.2
1.4
1.6
Rse
r [O
hm
*cm
²]
silver free silver
0.70
0.75
0.80
0.85
FF
silver free silver
20.0
20.5
21.0
21.5
22.0
22.5
23.0
eta
[%
]
gain in Jsc and Voc as well as low series resistance leads to high efficiency of transparent paste
fill factor is 4 % lower than silver containing pastes
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transparent front side paste –characterization
organic Ag gen. 1 Ag gen. 2 Ag gen. 3
1
10
100
sheet re
sis
tsance [m
Ohm
/sq]
paste
sheet resistance comparison of transparent and silver containing pastes
Resistance of transparent pastes ~ 10 times higher than silver paste
adding small amount (< 10 wt%) of silver nanowires to increase conductivity and maintain transparency
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conclusion
conductive polymers can be used for SHJ-front-side contact pastes
transparency increases Jsc and therewith efficiency in the range of conventional silver pastes can beobtained allready in this study
no paste transparent silver
35
36
37
38
39
40
Jsc [m
A*c
m²]
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conclusion
conductive polymers can be used for SHJ-front-side contact pastes
Transparency increases Jsc and therewith efficiency in the range of conventional silver pastes can beobtained allready in this study
sheet resistance somewhat to high adding of silver nanowires will decrease resistance and maintain transparency
no paste transparent silver
35
36
37
38
39
40
Jsc [m
A*c
m²]
organic Ag gen. 1 Ag gen. 2 Ag gen. 3
1
10
100
sheet re
sis
tsance [m
Ohm
/sq]
paste
© Fraunhofer
Thanks to the german Federal Ministry of Education and Research (MWT+ #03SF0420)…
…and you for your attention!
Further Informations:
Stefan Körner
+49-351-2553-7817
Fraunhofer Institut Keramische
Technologien und Systeme
Winterbergstraße 28, 01277 Dresden