two-dimensional modelling of the metallization induced
TRANSCRIPT
Two-dimensional modelling of the metallization
induced recombinative losses for screen printed
solar cells
Authors:
Lejo J. Koduvelikulathu, Sara Olibet, Valentin D. Mihailetchi, Dominik Rudolph, Enrique Cabrera, Radovan Kopecek
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Outline
2
Motivation
Experimental input
Modelling results
Conclusion
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Outline
3
Motivation
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Motivation
4
Line & Contact
resistance losses
pFF
FF
iVoc Voc
- Screen printed metallized cells
Recombination
losses
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
- Previous modelling studies
Emitter
Motivation
5
Bulk
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
- Inclusion of the experimental metal-Si interface microstructures
Motivation
6
Modelling using Silvaco ATLAS TCAD simulation suite
M.Hilali, PhD. Dissertation,2005
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Outline
7
Experimental input
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
The cell
8
110 µm front contacts
p-type Si; 2.5 Ω-cm
SiNx; ARC coating
n+ diffusion
Full Al- rear contact
Al-BSF
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Diffusions & Pastes
9
n+ diffusions
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Internal quantum efficiency
10
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Beneath the fingers
11
Topography
Conductivity
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Metal–Si interface microstructure
12
10%
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013 13
10%
Metal–Si interface microstructure
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013 14
Etching beneath the metal finger
Metal–Si interface microstructure
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013 15
Etching beneath the metal finger
Metal–Si interface microstructure
Experimental 4-pt
measurement
Few nm to 50 nm
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Modelling parameters
16
SiNx-Si (Spas)
5x105 cm s-1
3x105 cm s-1
1x105 cm s-1
Assumed Parameter
Fitted Parameter
Metal-Si (Smet) : 1x107 cm s-1 Glass-Si (Sglass) : 1x106 cm s-1
Ohmic metal contacts
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Outline
17
Modelling results
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Presence of only Ag-crystallites
18
Majority of current transport through direct contacts – Cabrera et.al,JAP -vol 110, 11
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
19
METAL BLOCK CRYSTALLITES Experiment
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
20
CRYSTALLITES No Ag-Crystallites Experiment
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
21
Crystallites Experiment No Ag-Crystallites
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Presence of only Ag-crystallites
22
Negligible drop in Voc and pFF
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Etching beneath the contact area
23
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
24
50 Ω /sq
65 Ω /sq
95 Ω /sq
Junction depth
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
25
50 Ω /sq
65 Ω /sq
95 Ω /sq
Junction depth
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
26
50 Ω /sq
65 Ω /sq
95 Ω /sq
Junction depth
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Etching beneath the contact area
27
Driving factor for the Voc and pFF losses
Deeper junction and not the sheet resistance
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Increased SiNx beneath metal finger
28
90%
50%
10%
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
29
Without front
Metallization
losses
Paste A
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Increased SiNx beneath metal finger
30
90%
10%
Higher SiNx presence, lower Voc and pFF loss
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Presence of Ag- crystallites
31
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
32
Etching beneath contact area
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
33
Etching beneath contact area
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
34
Etching beneath contact area
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Results
35
Etching beneath contact area
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013 36
Present model too sensitive to shunt scenarios
Presence of Ag- crystallites
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Outline
37
Conclusion
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Conclusion
38
Presented a novel model incorporating experimental metal-Si
microstructures
Ideal to have only small crystallite contacts without any emitter
etching
Si-etching during contact formation dominates the Voc and pFF
losses
Preferably localized opening of SiNx only where the current is
extracted
Model is more sensitive to shunts than experimentally observed
Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013
Acknowledgement
Thank You for Your Kind Attention
Acknowledges the EU commission & HIPERSOL consortium
Partly financially supported by EU within HIPERSOL: FP7- 228513