Direct write metallization for photovoltaic cells and scaling thereof

Atmospheric solution processing can help toward a significant cost reduction of photovoltaics. We investigate the use of direct write deposition approaches for deposition of metallization for a variety of solar cell materials. We are studying inkjet printing and aerosol spraying of metal contacts for Si, CIS/CIGS and organic photovoltaics. We have developed metal organic decomposition inks for metals such as: silver, nickel, copper and aluminum. All of these can be deposited in lines with 30-40 μm width and conductivities close to that of bulk metals. For silicon photovoltaics materials have been developed to facilitate Ohmic contact formation through an anti reflection coating. Initial research has been focusing on small cells, but in order to transfer the technology to production it has to be demonstrated on large area cells as well. For this the Atmospheric Processing Platform (APP) was developed at NREL. This platform allows us to scale the deposition of the developed inks and processing to large area (Up to 157 mm × 157 mm) and prototype contact patterns. The APP consists of several deposition, processing and characterization units, most located in a controlled environment. The atmospheric deposition tools in the APP are: inkjet printing, aerosol spraying and ultrasonic spraying. A rapid thermal processing unit is integrated for thermal processing. XRF and XRD can be accessed without leaving the controlled environment to determine the composition and structure of the deposited material. Sputter deposition and evaporation are also part of the APP, even though these techniques are not atmospheric. Details of the individual platforms in the APP will be given together with results of direct write contacts on large area cells.