A number of materials are used in the production of photovoltaic cells.They are either directly used,as in silicon for the substrate,or they are part of a processing step where the chemical is a reactant,catalyst or carrier.Beginning with the crystalline or multi-silicon substrate,gases are used for most of the steps in photovoltaic cell manufacturing.The silicon ingots are produced in a crucible where purge gases,for instance argon,are used to sweep impurities away from the silicon surface during the ingoting process.It is important that the incoming argon be of high purity to ensure that impurities are not present.If contaminates,such as oxygen,form impurities in the ingot it can result in shorter minority carrier lifetimes in finished cells.Some gas purifiers remove impurities below the part-per-billion measurement to enable higher ingot yields.These purifiers are designed to remove the major contaminates,as in CO,CO2,O2,NOx and other hydrocarbons.For continuous operations,purifiers are designed as part of systems which auto regenerate to enable continuous operation.Purifiers are typically used to improve the specification of facility gases or for applications where process gases are being reclaimed for re-use.Applications can range in flow rates from a few liters per minute for a single-ingot system to thousands of liters-per-minute for a facility wide purification system.In addition to silicon manufacturing,gases are used for doping,diffusion,annealing,deposition and other photovoltaic process steps.In critical deposition steps,process gas purity is of high importance to ensure maximum operating cell efficiencies.Gas purifiers can be utilized to remove impurities for most process gases including fluorinated,chlorinated and hydride gases,such as silane.Recommendations for gas purification for typical photovoltaic process gases will be reviewed.