High Photoconductive Vertically Oriented TiO2 Nanotube Arrays and Their Composites with Copper Phthalocyanine

Size-controllable and vertically oriented TiO2 nanotube arrays were fabricated by using anodic oxidation of pure titanium sheets in electrolyte solutions and were characterized by field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). A double-layered photoconductive device (Au/copper phthalocyanine/TiO2 nanotubes/titanium) was designed and fabricated based on the TiO2 nanotube arrays. The I−V curves demonstrated typical heterojunction characteristics and remarkable photoconductive performance for the devices. The effect of the thickness of copper phthalocyanine (CuPc) and the diameter of TiO2 nanotubes on the photoconductive property of devices was studied. The current value increased by 2 or 3 orders of magnitude when exposed to light from the dark, depending on the thickness of the CuPc layer and the diameter of TiO2 nanotubes.