Enhanced Charge-Collection Efficiencies and Light Scattering in Dye-Sensitized Solar Cells Using Oriented TiO₂ Nanotubes Arrays

Abstract

We report on the microstructure and dynamics of electron transport and recombination in dye-sensitized solar cells (DSSCs) incorporating oriented TiO2 nanotube (NT) arrays. The morphology of the NT arrays, which were prepared from electrochemically anodized Ti foils, were characterized by scanning and transmission electron microscopies. The arrays were found to consist of closely packed NTs, several micrometers in length, with typical wall thicknesses and intertube spacings of 8-10 nm and pore diameters of about 30 nm. The calcined material was fully crystalline with individual NTs consisting of about 30 nm sized crystallites. The transport and recombination properties of the NT and nanoparticle (NP) films used in DSSCs were studied by frequency-resolved modulated photocurrent/photovoltage spectroscopies. While both morphologies display comparable transport times, recombination was much slower in the NT films, indicating that the NT-based DSSCs have significantly higher charge-collection efficiencies than their NP-based counterparts. Dye molecules were shown to cover both the interior and exterior walls of the NTs. Analysis of photocurrent measurements indicates that the light-harvesting efficiencies of NT-based DSSCs were higher than those found for DSSCs incorporating NPs owing to stronger internal light-scattering effects.

Maximizing omnidirectional light harvesting in metal oxide hyperbranched array architectures

“…More recently, the synthesis of well-organized nanostructures such as the organized mesoporous TiO 2 films prepared using graft copolymer nanostructural polymers [6][7][8][9][10] , and some wellaligned one-dimensional (1D) nanostructures, such as nanowires (NWs), nanotubes, nanorods (NRs) and nanofibres, have stimulated intense research interest and attention owing to their potential advantages of rapid charge transport and efficient charge collection by means of providing short electrical pathways for rapid transfer and thus efficient collection of photo-generated carriers throughout the device [11][12][13][14][15][16][17] . It is well known that the key to high solar-to-electric efficiency is surface area.…”

Growth of TiO2 nanotube arrays with simultaneous Au nanoparticles impregnation: photocatalysts for hydrogen production

“…5,6 The main benefits are a simple synthetic procedure, enhanced charge transport properties and a cost-effective scale-up process. 7 In addition, self-organized TiO 2 NT arrays grown by anodization processes present enhanced photocatalytic activity when compared to randomly-oriented nanoparticles (NPs) or nanotubes prepared by other methods such as the sol-gel (hydrothermal) process. 7,8 One of the biggest limitations of TiO 2 is its relatively large band gap between 3.0 and 3.2 eV.…”

“…7 In addition, self-organized TiO 2 NT arrays grown by anodization processes present enhanced photocatalytic activity when compared to randomly-oriented nanoparticles (NPs) or nanotubes prepared by other methods such as the sol-gel (hydrothermal) process. 7,8 One of the biggest limitations of TiO 2 is its relatively large band gap between 3.0 and 3.2 eV. 9 Therefore, only UV light can be utilized for hydrogen production.…”

The use of Ti meshes with self‐organized TiO2 nanotubes as photoanodes of all‐Ti dye‐sensitized solar cells

“…Currently, the nanotubes have been shown to offer considerable improvement in the photo conversion of the DSSC which is attributed to improved electron transportation comparable to nanoparticles [12]. However, this research mainly focused on the Ti foil or TCO glass as the substrates coated with a nanotubular array layer [13][14][15][16].…”