6th Metallization Workshop Single print metal stencils for ...€¦ · Institute for Solar Energy...
Transcript of 6th Metallization Workshop Single print metal stencils for ...€¦ · Institute for Solar Energy...
Single print metal stencils for high-efficiency PERC
solar cells
H. Hannebauer1, T. Falcon2, J. Cunnusamy2, T. Dullweber1
1Institute for Solar Energy Research Hamelin (ISFH) 2ASM Alternative Energy
6th Metallization Workshop
Institute for Solar Energy Research Hamelin
Screen-printing is still the mainstream technique for front side metallization
Motivation
V. Shanmugam et al., IEEE Journal of Photovoltaics 5 (2), (2015), p. 525-533
Stencil-printing provides improved Ag finger profiles
Stencil-printing increases the conversion efficiency for narrow finger opening
Motivation
H. Hannebauer et al., Proc 5th Metallization Workshop, Energy Procedia 67, (2015), p. 108-115
Stencil-printing can reduce the silver finger paste consumption
Stencil Printed Ag Finger
A stencil features 100% open area in the aperture which leads to a benefit of excellent line height uniformity.
Width = 28 µm Height = 20 µm
Comparing screen and stencil technology
30 µm
• Stencil opening of 25 µm in combination with specific stencil Ag paste
• Two printing steps required for H-pattern design with stencil print for Ag fingers
• Novel Single Print Stencil combines advantage of one process step and excellent finger profiles
Screen Stencil
• VectorGuard Single Print Stencil prototype from ASM Alternative Energy
• Two layer metal foil; each layer being fabricated seperately
• Strong bond between two layers of nickel forming a single foil
• Top layer has a mesh grid over the busbar regions which acts as a bridge
• Finger regions are 100% open and fully stencil thickness
ASM AE VectorGuard Single Print Stencil prototype
Busbar
Finger
• Single Print (1x Print + 1x Dry)
• Dual Print (2x Print + 2x Dry)
+
Experiment plan
1st print: Screen 2nd print: Screen or Stencil
Screen or Stencil
Split groups of the experiment
Standard rectangular shaped five busbars in groups 1+3+4
Segmented five busbars with pads in group 2
Metal squeegee for stencils, polyurethane squeegee for mesh screens
Group Printing technique
Type of finger print
Ag finger aperture
[µm]
Ag paste
Finger paste consumption
[mg]
Busbar paste consumption
[mg]
Front Ag paste consumption
[mg]
1 Dual Print Stencil 30 A 86.0 14.2 100.2
2 Single Print Stencil 30 A - - 112.8
3 Dual Print Screen 40 B 59.9 14.2 74.1
4 Single Print Screen 40 B - - 91.5
Avg height = 12 µm Avg height = 22 µm Avg width: 47 µm Avg width: 36 µm
Impact of printing parameters on front grid resistance
Screen Stencil
Lf
ffinger r
AR =
ρ~Contribution of Ag finger to series resistance:
cmr screenL
Ω= 06.1, cm
r stencilLΩ
= 63.0,
0.05 Ωcm² increased Rs for screen-printing
ISFH PERC solar cell process
Rear protection layer
Texturing
Phosphorus diffusion
PSG + dielectric etch
Rear: AlOx/SiNy
Front: PECVD-SiNx
LCO at the rear
Al rear side metallization
Ag front side metallization
Co-firing
Wafer cleaning
PERC solar cell results
• Almost identical η for DP and SP with stencil finger print
PERC solar cell results
• Almost identical η for DP and SP with stencil finger print
• Voc gain for DP with non-firing through Ag busbar paste
PERC solar cell results
• Almost identical η for DP and SP with stencil finger print
• Voc gain for DP with non-firing through Ag busbar paste
• Jsc difference caused by 0.5%abs larger metallization area of screen print
PERC solar cell results
• Almost identical η for DP and SP with stencil finger print
• Voc gain for DP with non-firing through Ag busbar paste
• Jsc difference caused by 0.5%abs larger metallization area of screen print
• High conversion efficiency of 21.1% with novel single print stencil prototype on PERC solar cells achieved
• Single print stencil process saves one process step compared to dual print using a stencil while obtaining the same PERC cell performance
• Stencil print shows efficiency gain of 0.2%abs compared to today´s industrial screen print processes
Summary
We thank the German Federal Ministry for Economic Affairs and Energy
for funding part of this work under contract no. 0325753D (HighPERC) in
cooperation with
Acknowledgement