ZnO Film UV Photodetector with Enhanced Performance: Heterojunction with CdMoO4 Microplates and the Hot Electron Injection Effect of Au Nanoparticles.

A novel CdMoO4 -ZnO composite film is prepared by spin-coating CdMoO4 microplates on ZnO film and is constructed as a heterojunction photodetector (PD). With an optimized loading amount of CdMoO4 microplates, this composite film PD achieves a ≈18-fold higher responsivity than pure ZnO film PD at 5 V bias under 350 nm (0.15 mW cm-2 ) UV light illumination, and its decay time shortens to half of the original value. Furthermore, Au nanoparticles are then deposited to modify the CdMoO4 -ZnO composite film, and the as-constructed photodetector with an optimized deposition time of Au nanoparticles yields an approximately two-fold higher photocurrent under the same condition, and the decay time reduces by half. The introduced CdMoO4 microplates form type-II heterojunctions with ZnO film and improve the photoelectric performance. The hot electrons from Au nanoparticles are injected into the CdMoO4 -ZnO composite film, leading to the increased photocurrent. When the light is off, the Schottky barriers formed between Au nanoparticles and CdMoO4 -ZnO composite film block the carrier transportation and accelerate the decay process of current. The study on Au-nanoparticle-modified CdMoO4 -ZnO composite film provides a facile method to construct ZnO film based PD with novel structure and high photoelectric performance.