over 20% efficient n-type bifacial solar cell by industrial
TRANSCRIPT
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Cu-plated electrodes with green ns laser opening on
n-type silicon solar cells
Kuang-Chieh Lai, Shu-Yen Liu, Yueh-Lin Lee, Ming-Shiou Lin, Yun-Kuo Tsao, Chia-Chih Chuang, Chi-Chun Li and Chien-Chun Wang
Advance Technology Development Department
Motech Industries, Inc.
CC Li, Metallization Workshop, May 2, 2016
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CC Li, Metallization Workshop, May 2, 2016 2
Motech Industries, Inc.
Delaware, US Jiangsu, China
Hokkaido, Japan
Tainan, Taiwan
Motech Americas Itogumi Motech
Fab. I Fab II Fab. V Fab. VI ITC
SNE
TY Fab Taoyuan, Taiwan
Founded in 1983 Established Solar BU in 1997
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3 CC Li, Metallization Workshop, May 2, 2016
A Leading Solar Cell Manufacturer
Capacity (MW)
Source: HIS, PV Suppliers Tracker 2015Q3
0
500
1000
1500
2000
2500
3000
3500
4000
HanwhaQ-cells
Trina JA Yingli NSP Jinko Gintech CSI SuntechMOTECH
3.2GW cell production capacity in 2015 No.5 in the world
Smaller capacity of ingot growth, wafer slicing, module
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Motivation
Experimental Setup
Results & Discussion
Conclusion
CC Li, Metallization Workshop, May 2, 2016
Outline
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Reference: ITRPV 2016
CC Li, Metallization Workshop, May 2, 2016
Cell Efficiency; Market Share
N-type cells provide higher efficiency Projected growth of market share for N-type cells Cost needs to be controlled
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p-PERC HJT
IBC n-PERT
Boron emitter Phosphorous BSF
Passivation layer
Plated seed/Cu electrodes
Plated seed/Cu electrodes
Cu plating applicable to all types Si solar cells; more beneficial for n-type
CC Li, Metallization Workshop, May 2, 2016
Plating Application on Solar Cells
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Motivation
Experimental Setup
Results & Discussion
Conclusion
CC Li, Metallization Workshop, May 2, 2016
Outline
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Ag
Cell process flow
Schematic cross-section of the solar cell
Cu
Ni
n-type cell
P+
N+
Passivation
Sn Texture
Phosphorus doping (BSF)
Boron doping (emitter)
Front and rear passivation/ capping
Rear-side Ag printing and sintering
Front side laser opening
Plating Ni/Cu/Sn
CC Li, Metallization Workshop, May 2, 2016
Cell Structure and Process Flow
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Ag
Cu
Ni
n-t
ype
P
+
N+
Pas
siva
tio
n
Met
al s
ou
rce
― +
+
+
+
+
+
+
+
Applying a negative voltage to the rear contact of the cell, relative to the anode, making the cell in forward bias
Both Ni and Cu deposited using FBP -
- -
- -
CC Li, Metallization Workshop, May 2, 2016
Forward Bias Plating (FBP)
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Simple homemade equipment used for FBP and electroplating
Separate tanks for Ni, Cu, Sn
CC Li, Metallization Workshop, May 2, 2016
Lab Plating Equipment
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Motivation
Experimental Setup
Results & Discussion
Conclusion
CC Li, Metallization Workshop, May 2, 2016
Outline
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Tuning 532nm ns laser to achieve Removal of SiNx Thin line; uniform width Usable emitter
CC Li, Metallization Workshop, May 2, 2016
Tuning of Laser Process
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13 CC Li, Metallization Workshop, May 2, 2016
Ablation of SiNx
Elements Atomic%
Si 100.00
Elements Atomic%
Si 92.61
N 7.39
EDS used to verify the removal of SiNx
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Dielectric Layers Opening Width
Finger 1-5
Width (μm) 15.63 16.00 15.53 15.63 15.90
Ave. (μm) 15.74
Std. (μm) 0.20
Uniformity 1.49%
1 2
3 4
5 Contact opening width can be as low as 15um by 532nm ns laser
CC Li, Metallization Workshop, May 2, 2016
Contact Opening Width
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Finger Width after Plating processes
Finger 1-5
Width (μm) 45.80 46.37 45.90 46.50 46.13
Ave. (μm) 46.14
Std. (μm) 0.30
Uniformity 0.76%
1 2
3 4
5 Achieved <50um finger width for plated electrodes
CC Li, Metallization Workshop, May 2, 2016
FBP Metal Finger Width
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16 CC Li, Metallization Workshop, May 2, 2016
FBP Finger Shape
Isotropic deposition Overgrowth at the edges Finger aspect ratio depends opening and thickness
(a) laser (b) Ni
(c) Cu
~46μm
~20μm
~12μm
(d) Cu
~22μm
1kx 1.5kx
1kx 1kx
(e) Sn
~48μm
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R-line measurement showed Cu fingers much more conductive
CC Li, Metallization Workshop, May 2, 2016
Highly Conductive Cu Fingers
R-line (Ω/cm) r
(μΩ.cm) Finger 1 Finger 2 Finger 3 Finger 4 Finger 5 Avg.
Ag/Al paste
0.389 0.409 0.398 0.378 0.331 0.381 ~2.7
Cu plating
0.253 0.255 0.259 0.258 0.223 0.250 ~1.9
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18 CC Li, Metallization Workshop, May 2, 2016
Emitter Modification by Laser
1.0E+18
1.0E+19
1.0E+20
0 0.2 0.4 0.6 0.8
Bo
ron
co
nce
ntr
atio
n (
cm-3
)
Depth (m)
Laser process significantly changed emitter profile
Before laser 75 /sq
After laser 95 /sq
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19 CC Li, Metallization Workshop, May 2, 2016
Emitter Experiments
Various emitters tested for cell performance
shallow deep
heavy
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rc of printed Ag contact is generally 1~3 mΩ.cm2.
rc of NiSi silicide contact can achieve 0.1~0.001 mΩ.cm2 level with 1E19~5E19 cm-3 surface doping concentration
rc of NiSi silicide contacts Ref: Energy Procedia 38 ( 2013 ) 321 – 328
CC Li, Metallization Workshop, May 2, 2016
Contact Resistivity
TLM data of Motech plated cell
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Plated Cu Printed Ag/Al Paste
CC Li, Metallization Workshop, May 2, 2016
Plated vs. Printed
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I-V curve of Motech plated n-PERT solar cell
Best cell efficiency with different metallization
Conditions Eff. (%) FF Voc (mV) Jsc (mA/cm²)
Ag/Al paste 20.90 0.801 655 39.84
Ni/Cu/Sn 21.31 0.798 654 40.80
CC Li, Metallization Workshop, May 2, 2016
>21% Cell Efficiency
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18.50
19.00
19.50
20.00
20.50
21.00
21.50
7/15 9/3 10/23 12/12 1/31
Eff.(%)
0.638
0.640
0.642
0.644
0.646
0.648
0.650
0.652
0.654
0.656
0.658
7/15 9/3 10/23 12/12 1/31
Voc(V)
38.50
39.00
39.50
40.00
40.50
41.00
7/15 9/3 10/23 12/12 1/31
Jsc(mA/cm²)
0.750
0.760
0.770
0.780
0.790
0.800
0.810
0.820
7/15 9/3 10/23 12/12 1/31
FF
Acknowledgement: one-year grant from Ministry of Economic Affairs
CC Li, Metallization Workshop, May 2, 2016
Trend Chart of Cell Performance
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Motivation
Experimental Setup
Results & Discussion
Conclusion
CC Li, Metallization Workshop, May 2, 2016
Outline
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Demonstrated forward bias plating of Ni/Cu with 532nm ns-laser contact opening process
6” plated n-PERT solar cell reached efficiency 21.31%
Fine line capability
Highly conductive fingers
Continued development for
Contact performance
Adhesion
Reliability
CC Li, Metallization Workshop, May 2, 2016
Conclusion
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Thank You for Your Attention
CC Li, Metallization Workshop, May 2, 2016