Abstract: Photovoltaic (PV) devices employing layers of semiconducting carbon nanotubes as light absorption elements are disclosed. In one aspect a layer of p-type carbon nanotubes and a layer of n-type carbon nanotubes are used to form a p-n junction PV device. In another aspect a mixed layer of p-type and n-type carbon nanotubes are used to form a bulk hetero-junction PV device. In another aspect a metal such as a low work function metal electrode is formed adjacent to a layer of semiconducting nanotubes to form a Schottky barrier PV device. In another aspect various material deposition techniques well suited to working with nanotube layers are employed to realize a practical metal-insulator-semiconductor (MIS) PV device. In another aspect layers of metallic nanotubes are used to provide flexible electrode elements for PV devices. In another aspect layers of metallic nanotubes are used to provide transparent electrode elements for PV devices.