Polymer Thin-Film Dewetting-Mediated Growth of Wettability-Controlled Titania Nanorod Arrays for Highly Responsive, Water-Stable Self-powered UV Photodetectors

Holey layer of the TiO2 nanorod-covered surface obtained by the self-organization of polysterene (PS) templates is shown to achieve programmable wettability by creating nano- to micrometer-scale porosity, which is useful to demonstrate stable and self-powered Schottky junction-based UV photodetectors. The wettability characterized by static water contact angle (WCA) is found to be ∼40° (weak hydrophilic) with the nanorod film of micrometer-scale pores with a diameter of 9.91 μm and periodicity of 2.8 μm. In contrast, the holey layer of the TiO2 nanorod-covered surface with pores with a diameter of 90 nm and periodicity of pores of 1.4 μm shows a WCA ≈ 166°, which do not require any low surface energy coating and physical deposition techniques. A pure phase solution-processed superhydrophobic holey 1D TiO2 nanorod film in sandwiched configuration with platinized fluorine-doped tin oxide (FTO) electrodes shows self-powered and fast UV detection (rise time, ∼44 ms; decay time, ∼25 ms) with very high responsivity (25 A/W). The superhydrophobic sample hinders the water molecules from infiltrating into the sandwich junction, making the device performance extremely stable even in humid conditions.