Abstract
A single-walled carbon nanotube/anatase (SWCNT/anatase) composite thin film with a transmittance of over 70% in the visible-light region was fabricated on a quartz glass substrate by heat treating a precursor film at 500 °C in air. The precursor film was formed by spin coating a mixed solution of the titania molecular precursor and well-dispersed SWCNTs (0.075 mass%) in ethanol. The anatase crystals and Ti3+ ions in the composite thin films were determined by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The effect of the heating process on the SWCNTs was analyzed using Raman spectroscopy. The composite film showed an even surface with a scratch resistance of 4H pencil hardness, as observed using field-emission scanning electron microscopy and atomic force microscopy. The electrical resistivity and optical bandgap energy of the composite thin film with a thickness of 100 nm were 6.6 × 10−2 Ω cm and 3.4 eV, respectively, when the SWCNT content in the composite thin film was 2.9 mass%. An anodic photocurrent density of 4.2 μA cm−2 was observed under ultraviolet light irradiation (16 mW cm−2 at 365 nm) onto the composite thin film, thus showing excellent properties as a photoelectrode without conductive substrates.
Highlights
Photoelectrodes with a large area and high activity have attracted attention as essential for photovoltaic cells, sensors, and water-splitting devices [1,2,3,4,5]
The following sections describe the results obtained for these two electrodes, focusing on the changes in the SWCNTs above and inside the titania layer
The average diameters of the SWCNT bundles, which are clearly observed in the images of FTitania and FCOMP, were 14 ± 3 and 12 ± 3 nm, respectively
Summary
Photoelectrodes with a large area and high activity have attracted attention as essential for photovoltaic cells, sensors, and water-splitting devices [1,2,3,4,5]. The high resistivity of titania (1012 Ω cm at 25 ◦ C), which is related to enhanced electron–hole recombination, is a serious disadvantage, and facile photoelectrode fabrication without conductive substrates is still challenging [6,7]. Since their discovery by Iijima in 1991 [8], carbon nanotubes (CNTs) have emerged as promising nano-electronic materials because of their excellent electrical properties and thermal stability in oxidizing environments.
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