Fabrication of nanoporous TiO₂ films with novel surface morphology on conducting glass (FTO) substrate

Abstract

The crystalline structure and surface morphology of TiO₂ semiconductor coating play an important role in the conversion efficiency of dye-sensitized solar cells. In order to obtain TiO₂ coating with controllable morphology and high porosity, nanoporous TiO₂ films were fabricated on conducting glass (FTO) substrates, Ti thin films (1.5–2 μm) were deposited on conducting glass (FTO) substrates via the DC sputtering method, and then electrochemically anodized in NH₄F/ethylene glycol solution. The crystalline structure and surface morphology of the samples were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The influences of anodizing potential, electrolyte composition, and pH value on the surface morphology of nanoporous TiO₂ films were extensively studied. The growth mechanism of nanoporous TiO₂ films was discussed by current density variations with anodizing time. The results demonstrate that nanoporous TiO₂ films with high porosity and three-dimensional (3D) networks are observed at 30 V, when the NH₄F concentration in ethylene glycol solution is 0.3% (mass fraction) and the electrolyte pH value is 5.0.

Keywords

nanoporous TiO₂ films / anodizing potential / electrolyte composition / pH / conducting glass / growth mechanism

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