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Characterization of laser doped silicon and overcoming adhesion challenges of solar cells with nickel-copper plated contacts

: Geisler, Christian

Fulltext urn:nbn:de:0011-n-3604251 (4.5 MByte PDF)
MD5 Fingerprint: e19dfd4d83563dc117ce37d25a46c00b
Created on: 17.12.2015


Stuttgart: Fraunhofer Verlag, 2015, 195 pp.
Zugl.: Freiburg, Univ., Diss., 2015
Solar Energy and Systems Research
ISBN: 3-8396-0916-X
ISBN: 978-3-8396-0916-3
Dissertation, Electronic Publication
Fraunhofer ISE ()
Angewandte Forschung; applied research

The combination of localized laser patterning and metal plating allows to replace conventional silver screen printing with nickel-copper plating to form inexpensive front contacts for crystalline silicon solar cells. In this work, a focus is put on effects that could cause inhomogeneous metal deposition and low metal contact adhesion. A descriptive model of the silicon nitride ablation mechanism is derived from SEM imaging and a precise recombination analysis using QSSPC measurements. Surface sensitive XPS measurements are conducted to prove the existence of a parasitic surface layer, identified as SiOxNy. The dense SiOxNy layer is an effective diffusion barrier, hindering the formation of a nickel silicide interlayer. After removal of the SiOxNy layer, cells show severe degradation caused by metal-induced shunting. These shunts are imaged using reverse biased electroluminescence imaging. A shunting mechanism is proposed and experimentally verified. New laser process sequences are devised and proven to produce cells with adhering Ni-Cu contacts. Conclusively the developed processes are assessed based on their industrial feasibility as well as on their efficiency potential.