Nanostructured titanium dioxide/polytiophene photovoltaic devices

Nanostructured TiO2 thin films have been fabricated by glancing angle deposition (GLAD), and utilized as the electron acceptor in TiO2/polythiophene hybrid devices. TiO2 films were deposited on ITO coated glass by e-beam evaporation and were composed of a dense blocking layer (40 nm thick), and a columnar layer with a slanted post structure (400 nm thick). The slanted post layer was deposited using the Phi Sweep method, resulting in a column diameter of ∼20 nm. Hybrid materials were fabricated by spin casting regioregular poly(3-hexyl-thiophene-2,5-diyl) into the porous TiO2 film from chlorobenzene solutions. X-ray diffraction analysis of the as-cast polythiophene suggests that it is partially crystalline. Devices were completed by evaporation of a Ag back contact. Conversion efficiency of these devices was 0.10%. Hole mobility in these devices was measured using the time of flight technique, and a zero field mobility of 2.9×10⁻⁵ cm²/Vs determined.