Titania nanocomposite thin films with enhanced photovoltaic efficiency: Effects of Ti-alkoxide sol and compact layer

Titania nanocomposite thin films were prepared by spin-coating from sol–gel derived pastes of TiO2 powder in titanium isopropoxide sol and evaluated for light energy conversion in a photoelectrochemical cell. Addition of the Ti-precursor sol caused increases in film thickness, anatase content and photocurrent as well as a decrease in optical transmittance. Electrochemical impedance increased with increasing Ti-precursor amount in film, and the frequency peak in the Bode plot shifted toward a lower frequency. These suggest a longer electron lifetime in the composite film and the suppressed charge transfer from electrode to electrolyte, related to the aggregation of titania particles. Addition of a nanostructured titania compact layer between the composite film and the substrate caused a marked increase in the photocurrent, related to the rectifying behavior. Results demonstrate that these titania nanostructures promote electron generation and transport to enhance quantum efficiency.