Laser ablation of SiO 2 for locally contacted Si solar cells with ultra‐short pulses

• Published in: Progress in photovoltaics 2007-09, Vol.15 (6), p.521-527
• Main Authors: Engelhart, Peter, Hermann, Sonja, Neubert, Tobias, Plagwitz, Heiko, Grischke, Rainer, Meyer, Rüdiger, Klug, Ulrich, Schoonderbeek, Aart, Stute, Uwe, Brendel, Rolf
• Format: Article
• Language: English
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.758

We apply ultra‐short pulse laser ablation to create local contact openings in thermally grown passivating SiO 2 layers. This technique can be used for locally contacting oxide passivated Si solar cells. We use an industrially feasible laser with a pulse duration of τ pulse  ∼ 10 ps. The specific contact resistance that we reach with evaporated aluminium on a 100 Ω/sq and P‐diffused emitter is in the range of 0·3–1 mΩ cm 2 . Ultra‐short pulse laser ablation is sufficiently damage free to abandon wet chemical etching after ablation. We measure an emitter saturation current density of J 0e  = (6·2 ± 1·6) × 10 −13  A/cm 2 on the laser‐treated areas after a selective emitter diffusion with R sheet  ∼ 20 Ω/sq into the ablated area; a value that is as low as that of reference samples that have the SiO 2 layer removed by HF‐etching. Thus, laser ablation of dielectrics with pulse durations of about 10 ps is well suited to fabricate high‐efficiency Si solar cells. Copyright © 2007 John Wiley & Sons, Ltd.