Template‐Directed Liquid ALD Growth of TiO₂ Nanotube Arrays: Properties and Potential in Photovoltaic Devices

Abstract

Dense and well‐aligned arrays of TiO2 nanotubes extending from various substrates are successfully fabricated via a new liquid‐phase atomic layer deposition (LALD) in nanoporous anodic alumina (AAO) templates followed by alumina dissolution. The facile and versatile process circumvents the need for vacuum conditions critical in traditional gas‐phase ALD and yet confers ALD‐like deposition rates of 1.6–2.2 Å cycle−1, rendering smooth conformal nanotube walls that surpass those achievable by sol–gel and Ti‐anodizing techniques. The nanotube dimensions can be tuned, with most robust structures being 150–400 nm tall, 60–70 nm in diameter with 5–20 nm thick walls. The viability of TiO2 nanotube arrays deposited on indium tin oxide (ITO)–glass electrodes for application in model hybrid poly(3‐hexylthiophene) (P3HT):TiO2 solar cells is studied. The results achieved provide platforms and research directions for further advancements.

Precise control of highly ordered arrays of nested semiconductor/metal nanotubes

“…The SEM micrographs in Fig. 4 show an advanced multilayered nested nanotube structure within the pores of the Si template composed of a sequence of TiO 2 and Pt nanotubes (two in series), which has potential applications in photovoltaic devices [21]. TiO 2 layers were grown with titanium isopropoxide (Ti( i PrO) 4 ) and H 2 O at 250 °C [8].…”

Fabrication of alumina films with laminated structures by ac anodization

“…These products have been utilized in a variety of promising applications such as magnetic recording media [9–16, 33, 34], thermoelectric materials [17, 18], optical materials [20–22, 48, 49], sensors [23–25, 35], energy storage [25, 26, 36, 37, 50], photocatalysis [27, 51, 52], photovoltaic devices [28, 29] and biomaterials [53–56]. …”

Charge transport and recombination in dye-sensitized solar cells based on hybrid films of TiO2 particles/TiO2 nanotubes

“…Many researchers have reported that one-dimensional (1D) nanostructures [3][4][5][6][7][8][9][10] can be used in DSSCs in place of nanoparticles to facilitate the electron transferring. In addition to the unique electron properties, the 1D TiO 2 nanostructures have another function as light scattering materials with minimum sacrifice of the surface areas.…”

“…In addition to the unique electron properties, the 1D TiO 2 nanostructures have another function as light scattering materials with minimum sacrifice of the surface areas. The 1D TiO 2 nanostructures can either be fabricated perpendicular to the transparent electrode substrate [3][4][5][6][7] or randomly distributed during fabricating the TiO 2 photoanode based on nanoparticles [8][9][10]. Although the ordered TiO 2 nanostructures perpendicular to substrates can be more helpful for electron transport, the fabrication of these nanostructures in large area is still practically challenging.…”