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

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Summary

Introduction

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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