A photovoltaic cell structure is disclosed that includes a back contact layer that includes single wall carbon nanotube elements. The single wall carbon nanotube (SWNT) back contact is in electrical communication with an adjacent semiconductor layer and provides a buffer characteristic that impedes elemental metal migration from the back contact into the semiconductor active layers. In one embodiment, the SWNT back contact includes a semiconductor characteristic and a buffer characteristic. In another embodiment, the SWNT back contact further includes a metallic characteristic.