Enhancement of electron lifetime in dye-sensitized solar cells using anodically grown TiO2 nanotube/nanoparticle composite photoanodes

• TiO2 nanotube (NT) arrays were grown by potentiostatic anodization of Ti foil.
• Photoanodes were prepared by mixing NT powder into nanoparticle (NP) dispersion.
• DSCs were assembled with different NT content.
• The composite photoanodes show higher efficiency and electron lifetime than NP ones.

Dye-sensitized solar cells (DSCs) based on TiO2 nanotube/nanoparticle (NT/NP) composite photoanodes were fabricated including different NT content into the NP network. The NPs expose large surface area for the dye anchoring, while the incorporated nanotubes can improve the electron lifetime and scatter the incident photons enhancing the light harvesting. TiO2 NTs were fabricated by fast anodic oxidation of Ti foil and mixed into NP dispersion. Morphology of the as-grown NTs and of the prepared paste was investigated by means of Field Emission Scanning Electron Microscopy. DSCs were assembled and characterized by current–voltage electrical measurements and Incident Photon-to-electron Conversion Efficiency. Electrochemical Impedance Spectroscopy and Open Circuit Voltage Decay measurements were employed in order to study the recombination and to evaluate the electron lifetime into the anode materials. The overall photo-conversion efficiency of the NT/NP composite photoanode was found to be a 10% higher with respect to pure NP electrode evidencing an improvement of the charge lifetime.

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