Highly responsive UV-photodetectors based on single electrospun TiO2 nanofibres

Abstract

In this work we study the optoelectronic properties of individual TiO₂ fibres produced through coupled sol–gel and electrospinning, by depositing them onto pre-patterned Ti/Au electrodes on SiO₂/Si substrates. Transport measurements in the dark give a conductivity above 2 × 10⁻⁵ S, which increases up to 8 × 10⁻⁵ S in vacuum. Photocurrent measurements under UV-irradiation show high sensitivity (responsivity of 90 A W⁻¹ for 375 nm wavelength) and a response time to illumination of ∼5 s, which is superior to state-of-the-art TiO₂-based UV photodetectors. Both responsivity and response speed are higher in air than in vacuum, due to oxygen adsorbed on the TiO₂ surface which traps photoexcited free electrons in the conduction band, thus reducing the recombination processes. The photodetectors are sensitive to light polarization, with an anisotropy ratio of 12%. These results highlight the interesting combination of large surface area and low 1D transport resistance in electrospun TiO₂ fibres. The simplicity of the sol–gel/electrospinning synthesis method, combined with a fast response and high responsivity makes them attractive candidates for UV-photodetection in ambient conditions. We anticipate their high (photo) conductance is also relevant for photocatalysis and dye-sensitized solar cells.