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Paste development for electrochemical screen printing to structure metal layers of back contact solar cells

: Gensowski, K.; Kamp, M.; Efinger, R.; Klawitter, M.; Pospischil, M.; Eckert, J.; Bartsch, J.

Fulltext urn:nbn:de:0011-n-4774519 (729 KByte PDF)
MD5 Fingerprint: 4134f35dbba0e8312515d41c5edb6b39
Created on: 26.1.2018

Smets, A.:
33rd European Photovoltaic Solar Energy Conference and Exhibition, EU PVSEC 2017 : Proceedings of the international conference held in Amsterdam, The Netherlands, 25 September - 29 September 2017
München: WIP, 2017
ISBN: 978-3-936338-47-8
ISBN: 3-936338-47-7
European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) <33, 2017, Amsterdam>
Conference Paper, Electronic Publication
Fraunhofer ISE ()
Solarzellen - Entwicklung und Charakterisierung; Photovoltaik; Silicium-Photovoltaik; Kontaktierung und Strukturierung; etching; screen-printing; paste; solar cell

An electrochemical etching process is developed to realize the contact pattern of back contact solar cells. It combines ECM technology (Electrochemical Machining) with screen printing to allow local removal of metallic layers for maskless formation of electrically isolated conductive paths. The present work focused on waterbased paste development for this application. A plain sodium nitrate solution is used as electrolyte which allows electrochemical etching. Thickener and rheological additives are added to form a screen-printable paste. Additionally different additives are varied to improve printing paste behavior and printing results. The homogeneity of the printing paste is a major factor in the quality of etched structures. The multi-level homogenizing process developed in the present work reduces the particle size by about 35%. Using the optimized NaNO3-based paste, etched lines are formed in 100 nm aluminum layers by the Electrochemical Screen Printing (ESP) process. The smallest lines show widths of 80 μm and the adjacent aluminum regions are electrically separated up to a resistance of 1.6 MΩ. The process time is less than 2 seconds for 156x156 mm2 samples. Further process modifications ensure another particle size reduction of 33%. First IBC test structures are etched with line widths of 160 μm by using the novel process.