Two-dimensional modelling of the metallization induced

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


Outline

3

Motivation


Motivation

4

Line & Contact

resistance losses

pFF

FF

iVoc Voc

- Screen printed metallized cells

Recombination

losses


- Previous modelling studies

Emitter

Motivation

5

Bulk


- Inclusion of the experimental metal-Si interface microstructures

Motivation

6

Modelling using Silvaco ATLAS TCAD simulation suite

M.Hilali, PhD. Dissertation,2005


Outline

7

Experimental input


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


Diffusions & Pastes

9

n+ diffusions


Internal quantum efficiency

10


Beneath the fingers

11

Topography

Conductivity


Metal–Si interface microstructure

12

10%

Koduvelikulathu, Metallization Workshop, Konstanz: 07th-08th May-2013 13

10%



Etching beneath the metal finger



Etching beneath the metal finger


Experimental 4-pt

measurement

Few nm to 50 nm


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


Outline

17

Modelling results


Presence of only Ag-crystallites

18

Majority of current transport through direct contacts – Cabrera et.al,JAP -vol 110, 11


Results

19

METAL BLOCK CRYSTALLITES Experiment


Results

20

CRYSTALLITES No Ag-Crystallites Experiment


Results

21

Crystallites Experiment No Ag-Crystallites


Presence of only Ag-crystallites

22

Negligible drop in Voc and pFF


Etching beneath the contact area

23


Results

24

50 Ω /sq

65 Ω /sq

95 Ω /sq

Junction depth


Results

25

50 Ω /sq

65 Ω /sq

95 Ω /sq

Junction depth


Results

26

50 Ω /sq

65 Ω /sq

95 Ω /sq

Junction depth


Etching beneath the contact area

27

Driving factor for the Voc and pFF losses

Deeper junction and not the sheet resistance


Increased SiNx beneath metal finger

28

90%

50%

10%


Results

29

Without front

Metallization

losses

Paste A


Increased SiNx beneath metal finger

30

90%

10%

Higher SiNx presence, lower Voc and pFF loss


Presence of Ag- crystallites

31


Results

32

Etching beneath contact area


Results

33



Results

34



Results

35



Present model too sensitive to shunt scenarios

Presence of Ag- crystallites


Outline

37

Conclusion


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


Acknowledgement

Thank You for Your Kind Attention

Acknowledges the EU commission & HIPERSOL consortium

Partly financially supported by EU within HIPERSOL: FP7- 228513

Two-dimensional modelling of the metallization induced

Documents

Transcript of Two-dimensional modelling of the metallization induced