Low Temperature Laser Metallization for Silicon Solar Cells

Laser transferred contacts (LTC) feature low temperature contact formation, in addition to finger widths w < 30 mu m. The LTC process uses the laser induced forward transfer to deposit the contact metal on the solar cell. Here, a laser heats a thin metal layer through an optically transparent support. Modeling of the temperature distribution in the metal and the transparent glass support during laser heating illustrates that evaporating glass at the metal/glass interface propels the metal to the solar cell surface. The electrical contact to the solar cell emitter is directly formed during the transfer process through the anti-reflection coating of the solar cell. Since the laser transfer is not limited to a special material, a variety of contact metals can be used. Our LTCs are based on "clean" materials without heavy metals, like cadmium or lead. First solar cells with nickel/copper metallization result in a cell efficiency eta = 17.4% and a fill factor FF = 77.7%. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of SiliconPV 2011.