Ferro Electronic Materials has introduced two new rear aluminum conductor pastes, intended to reduce manufacturing costs while improving electrical efficiency and adhesion compared to currently available commercial products. AL 5130 and AL 5131 have pure aluminum metallurgy with high solids content and are claimed to enable fast printing at speeds of more than 200 millimeters per second. These new pastes react with silicon wafers and form very uniform and deep back-surface field (BSF) in the range of seven to ten microns without introducing recombination traps, helping to boost electrical efficiency.
The purpose of the aluminum is to reduce the ohmic contact resistance between the thick-film material and the p-doped silicon surface. However, material costs currently prevent a needed reduction in overall cell production costs. A reduction in material usage, while improving cell performance, offers the potential for lower cost-per-Watt processing.
Ferro’s new products allow cell manufacturers to reduce paste consumption by up to 20% and form a strong uniform back surface field (BSF) that increases absolute electrical efficiency by as much as 0.2% compared to competing products. They provide high adhesion to silicon and EVA film and enable the use of thinner cells that cut silicon costs. On silicon wafers with a thickness of 180 microns, bowing is less than 1.5mm with both pastes. AL 5130 and AL 5131 have pure aluminum metallurgy with high solids content and enable fast printing at speeds of more than 200 millimeters per second. The products are compatible with a host of back surface silver pastes from Ferro. They also form a bump- and bead-free surface over a wide co-firing process window, and are dust-free and scratch-resistant for ease of wafer handling.
Back surface field on crystalline silicon photovoltaic devices.
AL5130 and AL5131 aluminum pastes are RoHS- and REACH-compliant; AL 5130 is free of lead, cadmium, and phthalates. The pastes were developed to accommodate a range of texturization processes used by customers.
August 2011 onwards.