Nature of the Ag-Si Interface in Screen Printed Contacts: A Detailed Transmission Electron Microscopy Study of Cross-Sectional Structures

As screen printed contacts are the predominant metallisation technique in industrial production of Si solar cells, a better understanding of their properties is necessary. In this work, we show that high-quality cross-sectional samples can be prepared, whose study by transmission electron microscopy (TEM) reveals precisely the structure of the contact between the silver fingers and the Si. On diffused [100] Si wafers, direct firing of an Ag paste results in interfaces which are mainly composed of shaped Ag crystallites penetrating the emitter up to 120 nm. These crystallites are in epitaxial relation with the Si substrate. When firing the contacts through a SiNx layer, larger Ag crystallites are present at the interface with Si and the orientation relation is lost. In both cases, high resolution TEM imaging and EDX analyses reveal a crystalline Ag/Si interface, where neither oxide nor glass frit can be detected. The presence of a significant glass frit l ayer between the Ag crystallites contacting the Si and the large Ag grains forming the bulk of the fingers can partly explain why lowly doped emitters are difficult to contact by screen-printing.


Published in:
IEEE Electron Devices Society: 29th IEEE Photovoltaic Specialists Conference 2002, 360-363
Presented at:
29th IEEE Photovoltaic Specialists Conference 2002, New Orleans, May 20-24, 2002
Year:
2003
Laboratories:




 Record created 2010-02-17, last modified 2018-09-13


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