An ultraviolet photodetector based on conductive hydrogenated TiO₂ film prepared by radio frequency atmospheric pressure plasma

Abstract

The growing demand for real-time ultraviolet (UV) monitoring calls for a simple, rapid, and low-cost strategy to prepare UV photodetectors (PDs). We prepare a wearable real-time UV PD based on hydrogenated titanium dioxide film synthesized by radio frequency atmospheric pressure plasma. The conductivity of our hydrogenated titanium dioxide is improved to 10.2 S cm−1, nine orders of magnitude higher than that of pristine titanium dioxide after 10 min plasma treatment. Plasma hydrogenation disrupts the surface crystal structure, introducing oxygen vacancies (OVs) that create self-doped titanium(III) and titanium(II) species. First-principles calculations indicate that the OVs raise the Fermi level of TiO2 and distort the lattice locally. Our optimized film has a distinctive periodic switching characteristic under intermittent illumination; its responsivity is good from 280 to 400 nm, peaking at 632.35 mA W−1 at 365 nm. The fabricated wearable sensor based on the optimized film effectively monitors the daily variation of ambient UV intensity in three typical weather types, transferring its data to a smartphone via Wi-Fi.