Low-Temperature Solution-Processed Synthesis of Hollow SnO₂@TiO₂ Core–Shell Hierarchical Structure for Self-Powered Ultraviolet Photodetectors

The interest in investigating hollow core–shell nanostructures was stimulated by their intrinsic advantage in light absorption and photocarrier separation for promising applications in photoelectrochemical devices. Here, SnO₂@TiO₂ core–shell hierarchical tubular structure was designed and prepared via a low-temperature solution route using carbon nanofibers as templates. The heterostructure consists of SnO₂ nanotubes and TiO₂ nanocones, which facilities photocarrier separation and transport by built-in electric field at their interface, and direct transport path served by SnO₂ nanotubes. The large specific surface area was also believed to contribute to improve performance by providing more active sites for chemical reactions. After assembling into a photoelectrochemical-type ultraviolet photodetector, the detector exhibits a high short-circuit photocurrent density of 870 μA cm^–2 under ultraviolet illumination (λ = 365 nm) of 35 mW cm^–2 without bias voltage. The photosensitivity can reach up to 3781, and the feature response time was in microseconds, 33 ms for rise process and 13 ms for decay process. It is believed that this structure with combined advantageous features is extendable to other photoelectrochemical cases, such as dye-sensitized solar cells and artificial photosynthesis.