module integration for back contact back junction solar...
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module integration for back contact back junction
solar cells
Andreas Halm1, Bart de Gier2,, Valentin D. Mihailetchi1, Haifeng Chu1, Giuseppe Galbiati1, Razvan Roescu1, Joris Libal1, Radovan Kopecek1, Nico van Ommen2,
Andreas Schneider1
1: International Solar Energy Research Center - ISC Konstanz
2: Eurotron BV
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
Introduction: IBC module
2
Advantages:
• highest power potential
• uniform optical appearance
Challenges:
• CTM losses
• interconnection method
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
Introduction: Zebra cell
3
Low cost IBC cell
Screen printed 3D metallization
6 inch n-type Cz wafer
Bifacial IBC cell
Front floating junction
Industrial processes proven in PERC
and PERT fabrication
» Current best efficiency: 22 %
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016 4
standard H-pattern cell
electrical losses:
• series resistance
optical losses and gains:
• absorption in glass and
encapsulant layer
• reflection at the interfaces
• reflection from front metallization
• reflection from backsheet
IBC cell
more liberty since all metal
is on the rear side
higher CTM loss in ISC
increases ISC for bifacial
IBC cells
thinner front encapsulation
implementable
Introduction:
main CTM power losses
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016 5
-> electrical isolation on cell
or module level needed
Introduction: interconnection issues
3D metallization of Zebra cell
Contacting of both polarities in one plane:
-> compensation of
mechanical stress for single
sided contacting needed
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
multi busbar
many other great concepts……
Introduction:
possible interconnection concepts
6
Classical way:
adapted tabber-stringer
conductive backsheet
NICE
weaving
smartwire
new approaches:
dedicated equipment
Edge stringing
(Sunpower)
Continous stringing
( e.g. ISC)
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
Introduction:
possible interconnection concepts
7
Classical way:
adapted tabber-stringer
conductive backsheet
new approaches:
dedicated equipment
Continous stringing
( e.g. ISC)
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
Outline
8
ribbon based Zebra modules
• contacting scheme
• bifacial module measurements
• reliability
Zebra modules assembled with conductive backsheet
• device optimization
• results on 60 cell modules
• cost structure
outlook and summary
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
ribbon based interconnection
9
advantages and challenges:
+ easy built-up for cells with asymmetric
BB structure
+ existing technology with long term
experience
+ bifaciality implementable
+ El inspection of string possible
- special upgrade for stringer needed
- bowing problem
S. Kaufmann, 4th MWT WS, Amsterdam, 2012
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
ribbon based interconnection:
contacting scheme
10
assembly process at ISC to overcome excessive bowing
a) soldering of stress relieved ribbon
b) gluing of electrically conductive adhesive (ECA)
+ long term stability
- high mechanical stress
+ low mechanical stress
- reliability ?
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
ribbon based interconnection:
performance
11
Both techniques yield similar results !
- > choice of ribbon main factor for
series resistance losses
module Voc (V) Isc (A) FF (%) Pmpp (W) Eta (%) CTM power
(%)
bifi module front side 2.65 9.85 76.8 20.0 20.2* 1.5
bifi module rear side 2.62 7.03 78.0 14.3 14.4*
bifi factor: P rear / P front = 0.71
*measured with black frame in 1 mm distance to edge cells
best results so far:
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
ribbon based interconnection:
bifacial measurements
12
bifaciality factor: PREAR / PFRONT = 0.77
both side illuminated IV measurements on a one-cell-module:
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
ribbon based interconnection: reliability
13
TC 200 testing of soldered one-cell-modules:
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
ribbon based interconnection: reliability
14
temperature cycle testing up to TC 1000 for ECA glued one-cell modules:
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
conductive backsheet (CBS) approach
15
Pick and place: low stress on cell
Cu backsheet: low Rseries
Small cell spacing
Flexible rear design
Proven in mass production
» Good candidate for fast
transfer to industry
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
CBS: contact optimization with ECA
16
Contact resistance measurements:
Measured quantity:
RC system = RC1 + RC2 + RVol (h)
h : contact height
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
CBS: optimization of contact pattern
17
ECA consumption per cell (mg)
rel. C
TM
FF
dro
p (
%) 6
9 13
18 22
6
9
-> quantity of contact points more significant that contact area
optimization on ECA layout: points versus 3mm lines
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
CBS: reliability
18
temperature cycle testing up to TC 1000:
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
CBS: 60-cell Zebra modules
19
Module production at Eurotron´s competence
center:
Isc (A) Voc (V) FF (%) PMPP (W)
Module A 9.97 39.3 77.1 303
CTM (%) -0.6 0.00 1.8 1.1
Module B 9.94 39.2 76.5 298
CTM (%) -0.7 -0.05 2.4 1.7
Module C 9.84 39.1 76.3 294
CTM (%) -0.6 0.04 2.3 1.8
IMPP (A) PMPP (W)
Group Mean Std. Dev. Mean Std. Dev. Ʃ PMPP (W)
A 9.18 0.016 5.10 0.026 306
B 9.13 0.016 5.06 0.03 304
C 9.07 0.019 4.99 0.037 299
Cell preparation at ISC Konstanz during Hercules pilot
line experiment:
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
CBS: certified module measurement
20
ISE Callab measurement:
Module ISC (A) VOC (V) FF (%) PMPP (W)
IV @ Callab B 9.94 39.24 76.5 298.3
Full area efficiency: 18.4 %
Total aperture efficiency: 19.1 %
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
Module configuration Power (W)
Current status 303
Use 22 % cell efficiency instead of 21.4 % 311
Introduce M2 wafers (now M0) 319
Increase cell spacing from 1.25 to 4 mm 322
Module Technology Area (m²) Cells / Size Power (W)
SunPower N IBC 1.66 96 / 5 inch 345
LG N PERT 1.64 60 / 6 inch 320
Zebra N IBC 1.62 60 / 6 inch 303
Yingli N PERT 1.63 60 / 6 inch 300
Solarworld P PERC 1.68 60 / 6 inch 295
Trina P PERC 1.63 60 / 6 inch 290
CBS: Short term improvements
21
Comparison to example high end c-Si modules on the market:
Calculated power increase with identical cell and module process:
next week:
Module Technology Area (m²) Cells / Size Power (W)
SunPower N IBC 1.66 96 / 5 inch 345
Zebra N IBC 1.68 60 / 6 inch 322
Yingli N PERT 1.63 60 / 6 inch 300
Solarworld P PERC 1.68 60 / 6 inch 295
Trina P PERC 1.63 60 / 6 inch 290
today:
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
CBS: CoO calculation
22
$-
$0.100
$0.200
$0.300
$0.400
$0.500
$0.600
p-type PERC ZEBRA
US
D/W
p
module transformation cost
(USD/Wp)
Labour (cell)
Yield loss (cell)
Waste disposal (cell)
Utilities (cell)
Wafer
Materials/Consumables (cell)
Depreciation (cell)
Cell efficiency: 20.5% 22%
Module power: 300 W 322 W
Ʃ 0.46 $/W
∆ = 4.5 ct /W
Ʃ 0.55 $/W
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
Outlook: Zebra half cell module
23
Isc (A) Voc (V) FF (%) PMPP (W)
Module* 5.0 79.0 77.3 308
CTM (%) -2.8 0.05 0.4 -3.2
* measured at EDF
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
Outlook: new concept
24
Bifacial conductive backsheet - proof of concept :
First prototype Pfront = 18.1 W, bifaciality factor = 0.7 (produced at ISC Konstanz)
(designed by ISC Konstanz
produced by Coveme)
Transparent rear backsheet
with copper tracks:
Bifacial Zebra module:
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
Outlook:
outdoor performance 4 cell modules
25
sp
ec
ific
en
erg
y (
Wh
/Wp
ea
k)
Outdoor performance Zebra modules measured
between 12-2015 and 05-2016
+ 11 %
+ 21 %
100 %
std. CBS
bifi CBS
bifi ribbon
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
Summary
26
− ribbon interconnection possible for Zebra cells soldered or ECA glued
− bifacial 4-cell module with 20.2 % front efficiency and 71 % bifi factor
− Assembly of Zebra cell in conductive backsheet module possible
− 60-cell module with 303 W power output based on industrial cell and module
processes and 308 W module with 120 half cells
− Short term improvements up to 322 W feasible with competitive cost structure
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A. Halm, 2nd HERCULES workshop, Berlin, October 2016
Acknowledgement
27
The project HERCULES has received funding from the European Union’s Seventh Programme for research,
technological development and demonstration under grant agreement No 608498
Thank you for your attention !