Novel Ω-Shaped Core-Shell Photodetector with High Ultraviolet Selectivity and Enhanced Responsivity

The design of nanostructure plays an important role in performance enhancement of low-dimensional optoelectronic devices. Herein, a novel photodetector (PD) based on electrospun SnO2 nanofibers with Omega-shaped ZnO shell (SnO2@ZnO) is fabricated. With 87.4% transmittance at 550 nm, SnO2@ZnO PD exhibits a high photo-to-dark current ratio up to 10(4) at around 280 nm. Owing to the additional Omega-shaped ZnO shell, SnO2@ZnO PD possesses a responsivity of nearly 100 A W-1 under 5 V bias and the illumination of 250 nm light, which is 30-time enhancement of pristine SnO2 PD. The enhancement is mainly attributed to type-II energy band structure. Furthermore, by changing the direction of incident light, SnO2@ZnO PD has a high UV selectivity with an UV-vis rejection ratio (R-250 nm/R-400 nm) as much as 2.0 x 10(3) at 5 V bias under back illumination, which is fourfold higher than that under face illumination. The UV selectivity improvement may be attributed to light confinement in the Omega-shaped structure. With both theoretical simulations and experimental comparisons, it is demonstrated that the unique compact Omega-shaped nanostructure does contribute to photon trapping and gaining process, especially in back-illumination configuration. The approach can be easily extended to other materials, preparing novel building blocks for optoelectronic devices.