www.ecn.nl

Backside metallization of bifacial n-Pasha cellsBob Wind

n-Pasha cell

n‐type Czp+ emitter

n+ BSF

Purpose

• Find minimal line width (practice deviates from theory)• Find specific contact resistivity (needed for pattern optimization)

Rcontact

Metal fractionMinimal linewidth

Theory

Practice

Theory

∆PPFF FF ∙ ∙ /

= C

Experimental setup

• 4 cells per wafer• 2 different pastes

Varying metal fraction

• Two groups:• Group 1: change # lines     (keep linewidth constant = 110μm)• Group 2: change linewidth (keep # lines constant = 55)

30lines 44lines

66lines 124lines

50μm 75μm

100μm 150μm

Calculating Rseries

FF  and  PFF                          Rseries

X‐coordinateY‐coordinate

Metal design (lines‐line width) 

Isc(A) Voc(V) FF PFF  Fraction(%) Rseries(Ω)

10‐110μm 2.284 0.626 0.709 0.797  4.59 0.05815‐110μm 2.291 0.638 0.755 0.796  5.28 0.02620‐110μm 2.290 0.637 0.767 0.798  6.84 0.02030‐110μm 2.296 0.638 0.777 0.796  8.09 0.01230‐110μm 2.285 0.633 0.783 0.821  7.81 0.011544‐110μm 2.285 0.632 0.788 0.821  10.53 0.010366‐110μm 2.283 0.633 0.791 0.818  14.38 0.0085124‐110μm 2.282 0.631 0.794 0.819  25.10 0.0080 

Rseries to metal fraction

Minimal linewidth lies outside of current research range

from #lines screen

,#

= 0,13 ∙ +0,029 ∙ ) ∙#

C

Conclusion & Outlook

• In current technology line width is not yet crucial.

• Within ECN we now have a quite straight forward experimental method to determine 

• Next steps: – Verify different metallization methods (for instance plating)– Front side metallization– Define optimal pattern for n‐Pasha depending on metallization method 

Thank you for your attention

Thanks to Eric Kossen, Kees Tool, Ingrid Romijn, …