Low Cost Metallization Inks for Photovoltaics

Commercial Si wafer solar cells employ screen printed Ag grids as the front contact and Al layers as the back contact. The drive to decrease cost is pushing manufacturers to seek both lower cost materials and methods. One obvious material change is to replace Ag with lower cost metals such as Ni and Cu. Shifting to thinner Si wafers is another reasonable cost saving measure, but it will also necessitate replacing contact methods like screen printing. Inkjet and aerosol jet printing are excellent non-contact choices. These tools have been incorporated into NREL's Atmospheric Processing Platform, along with complementary rapid thermal processing capabilities. We have used these tools to deposit Ni/Cu bilayer grids as the front contacts and Al layers as the back contacts on 21 cm² Si solar cells. To our knowledge, this is the first time all non-contact printed metal contacts on Si solar cells have been demonstrated. These studies also show the potential of non-contact printed Al, Ni, and Cu inks to contribute to the fabrication of low-cost photovoltaic devices.