TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Photovoltaic Cell: The semiconductor layer comprises elemental silicon/germanium. The elemental silicon/germanium comprises an n-type dopant or p-type dopant at a concentration from 1 x 1014 to 1 x 1016 atoms per cubic centimeter. The semiconductor layer has an average thickness of 5-300 microns. The doped domains have an average depth of 250 nm to 2.5 microns. The spacing between the n-doped domain and the adjacent p-doped domains has a value at one or more locations of 20-200 microns. The doped domains have an average dopant concentration of 1.0 x 1018 to 5 x 1020. A photovoltaic cell comprises a semiconductor layer, an n-doped domain and a p-doped domain along a surface of the semiconductor layer at the same level as each other where the doped domains each have a planar extent along the surface comprising a stripe having a ratio of the average length that is at least about a factor of 10 greater than the average width and a spacing between the n-doped domain and the p-doped domain has a value at one or more locations of 10-500 microns. Each of the doped domains have a planar extent along the surface comprising a stripe having a ratio of the average length that is at least a factor of 15 greater than the average width. A photovoltaic cell comprises a semiconductor layer, an n-doped domain and a p-doped domain along a surface of the semiconductor layer where the doped domains each have a planar extent along the surface comprising a stripe having a ratio of the average length that is at least about a factor of 10 greater than the average width, a dielectric layer over the doped domains and patterned metal interconnects, where the dielectric layer comprises windows that expose 5-80% of each of the doped domains and where the metal interconnects over the windows with the metal interconnects have an area at least 20% greater than the area of the windows. The windows expose 10-70% of each of the doped domains. The metal interconnects over the windows with the metal interconnects having an area at least 100% greater than the area of the windows. Preferred Method: In the method for doping a semiconductor along a selected pattern, the energy beam comprises an infrared laser. The dopant is driven down to a depth of 100 nm to 5 microns. The first doped domain comprises a stripe having a ratio of the average length that is at least about a factor of 10 greater than the average width.