Title:	An Investigation of an Atmospheric Screen-Printable Cu Paste and Rapid Thermal Sintering Contact for Cost-Effective Silicon Solar Cell
Author(s):	A. Ebong, K. Ren, S. Huneycutt, R. Dharmadasa, K. Ankireddy, T. Druffel
Keywords:	Silicon (Si) Solar Cells, Metallization, Screen-Printed Cu Paste, Fire-Through Dielectric Contact
Topic:	Silicon Materials and Cells
Subtopic:	High Temperature Route for Si Cells
Event:	37th European Photovoltaic Solar Energy Conference and Exhibition
Session:	2DV.3.28
Pages:	536 - 539
ISBN:	3-936338-73-6
Paper DOI:	10.4229/EUPVSEC20202020-2DV.3.28
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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For a cost-effective silicon solar cell, the metallization cost can be decreased by the use of copper (Cu), whose conductivity is close to that of silver (Ag), but approximately one hundred times lower in cost. Traditionally, Cu is applied through plating, which requires additional nickel (Ni) and forming gas anneal to form nickel silicide (NiSi) for blocking the Cu diffusion into silicon (Si), one of the challenges of using Cu. However, the wet chemistry process is cumbersome and expensive, the industry is still evaluating the long term reliability of this product. Therefore, there is an urgent need for developing an atmospheric screen-printable Cu paste that mimics the usual industry practice with Ag paste. This will be advantageous to the manufacturing of high-throughput, high-efficiency Si solar cells without additional capital equipment investment and leads to cost reduction in the metallization step. Hence, the formulated screen-printable Cu paste must address the challenges of (i) Cu oxidation in the atmosphere and (ii) the fast diffusion of Cu into Si at elevated temperature. This paper reports on the atmospheric screen-printable Cu paste that has fired through the dielectric coating to form an excellent contact with the Si and has shown some promising electrical output parameters. The electrical output parameters of the cells suggest that Cu is sequestered in the reformed metal-oxides after high temperature sintering in the belt furnace at peak temperatures ranging from 590-700 oC, and did not diffuse into Si as supported by the unity or near unity ideality factor. This is great news for the solar community that a screenprintable Cu paste is printed, dried and sintered through the dielectric to contact the Si underneath in the atmosphere without shunting the junction.