PNL-3234 UC-63 FI GURES TABLES some of the general cell types and, in some cases, several candidate materials for a particular device function are examined. Examples are the homojunction, heterojunction and r~IS structures possible for polycrystalline Si cells and the use of either ITO or Sn0 2 as the window layer of the heterojunction structure. Also selected for study by the workshop participants were the processes listed below for fabrication of materials used in the selected cell types. These processes are examined in this study for materials usage efficiency: