evaluation of via pastes for p and n type metal wrap through mwt solar cells

• DOI: 10.4229/27theupvsec2012-2ao.2.6
• Publication Date: 2012-01-01
• Authors: Daniel Biro; Sabrina Lohmüller; Florian Clement; Andreas Wolf; Elmar Lohmüller; Benjamin Thaidigs...; Ralf Preu
• Keywords: 0202 electrical engineering, electronic engineering, information engineering; 02 engineering and technology; Wafer-Based Silicon Solar Cells and Materials Technology; 7. Clean energy; Silicon Solar Cell Improvements

27th European Photovoltaic Solar Energy Conference and Exhibition; 590-595<br/>Via metallization is a main challenge in fabrication of metal wrap through (MWT) solar cells. Special attention has to be given to the right choice of both metallization paste and suction process, in order to ensure a low via-related series resistance. Five out of six via pastes investigated show average via resistances of less than 4 mΩ by using an appropriate suction process. The contact formation of the via paste to the base is also of particular interest since in more advanced MWT structures no rear emitter is present, as for example the high-performance MWT (HIPMWT) approach on p-type silicon. The contact separation and minimum leakage current to the base has to be ensured by the non-contacting via paste itself. Dark current-voltage characteristics in forward and reverse bias condition show quite different behavior for each of the six via pastes tested on p- and n-type test structures. The obtained results are very promising for a transfer of the HIP-MWT concept to n-type silicon. With completely screen-printed contacts, a large-area p-type float-zone silicon HIP-MWT solar cell reaches a peak conversion efficiency of 20.3% and confirms the high potential of the HIP-MWT structure for industrial fabrication of passivated MWT solar cells.<br/>