Preparation and UV Photoelectric Properties of Aligned ZnO–TiO₂ and TiO₂–ZnO Core–Shell Structured Heterojunction Nanotubes

Abstract

Large-area horizontal-aligned ZnO nanotubes (ZNTs), TiO2 nanotubes (TNTs), TiO2–ZnO core–shell nanotubes (TZNTs) and ZnO-TiO2 core–shell nanotubes (ZTNTs) were successfully synthesized by electrospinning combined with pulsed-laser deposition. The morphology, structure, and composition of the samples were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. The photoluminescence (PL) spectra of these samples indicate that the addition of a TiO2 layer greatly decreases the recombination of photogenerated carriers in the heterojunction nanotubes. The photodetectors (PDs) were fabricated by assembling horizontally ordered nanotubes on the gold interdigital electrode, and their ultraviolet (UV) detection performances were compared. The test results at room temperature show that the PD with aligned ZTNTs have the best UV response and a short response recovery time. In addition, the performance of ZTNT PDs and TZNT PDs are further improved under heating. The photo/dark current ratio, responsivity (R λ), detectivity (D*), and external quantum efficiency (EQE) of ZTNTs increased to 388, 450 uA·W–1, 1.1 × 1010 cm·Hz1/2·W–1, and 0.15%, respectively, under the condition of 365 nm UV radiation with a power density of 4.9 mW·cm–2 and a 1 V bias at 90 °C. The UV response mechanism and structural superiority of the horizontally ordered coaxial heteronanotube were also discussed. In addition, this work provides an important method for the design of other ordered nanomaterials and structures, which have a wide range of applications in the fields of sensors, transistors, transparent flexible electrodes, and other multifunctional devices.

Polypyrrole Film Deposited-TiO2 Nanorod Arrays for High Performance Ultraviolet Photodetectors

“…Figure S2: The I-V curves of the FTO-3PPy-TiO 2 -FTO device. Table S1: The comparison of results between previous reported PDs and our devices [20,[38][39][40][41].…”

Structural, morphological, optical and electrochemical characterization of Ag2O/ZnO and ZnO/Ag2O nanocomposites

“…The photocatalytic activity of metal oxide nanoparticles is closely associated with the surface morphology [5]. The ZnO nanoparticles with hierarchical and hexagonal-like morphology demonstrated attracting application in degradation of textile dyes due to the increased optical absorption efficiency and high specific surface area [6,7]. However, because of the wide band gap of ZnO (3.2 eV), only limited range of solar radiation can be used and the photogenerated charge carriers are liable to recombination, leading to low quantum yields.…”

Improved Photoresponse Characteristics of a ZnO-Based UV Photodetector by the Formation of an Amorphous SnO2 Shell Layer

“…Accordingly, there is a trade-off between the high photoconductive gain and the fast light response speed. To improve their rise and fall times without degrading the photoconductive gain, introducing a shell layer to the ZnO core, such as AIN [18], Al 2 O 3 [22], InN [23], SnO 2 [24], PVA [25], CuCrO 2 [26], or TiO 2 [27], may be a promising solution, resulting in an improvement in the overall performance of PDs. However, forming the shell layer of these materials requires a high temperature and is a complex and expensive process.…”