The Fabrication And Properties Of ZnO Nanowires Based Self-Powered PECC Type UV Detectors

Ultraviolet (UV) photodetectors have been widely utilized in civil life and military applications. Until now, silicon based UV detectors have dominated the main market for their high sensitivity, high signal-to-noise ratio and high response speed during the detection. In late 1980s, as the grown technology developes rapidly, wide band gap semiconductor will replace Si for the fabrication of photodetectors and has enormous potential and broader prospects. Compared with photodetectors based on Si, devices based on wide band gap semiconductors can avoid the use of expensive optical filter and realize visible-blind detection. Wide band gap based photodetectors, which have been used in the fields such communication and astronomy, have attracted lots of attention.Over the past two decades, with thermal and chemical stability, the wide bandgaped ZnO (3.37 eV at room temperature) has drawn increasing attention for its great deal of potential in optoelectronic devices. Up to now, much progress in UV detectors based on ZnO has been made. Detectors with different structures have been reported, such as metal-semiconductor-metal (MSM), p-i-n, p-n junction, and Schottky barrier planar-type structures etc. However, rigid epitaxial processes, single-crystal substrates and external applied voltage are usually demanded, which will generate high production cost.The photoelectrochemical cell (PECC) type UV detector is able to transfer the optical signal to electrical signal directly without external applied voltage, it is self-powered. Moreover this self-powered photodetector needs no intricate fabrication process and demonstrates fast photoresponse speed, it is promising to become a mainstream detector in the future. However, related reports are very limited, especially the ZnO based ones. The reported detecting abilities are limimited so far, therefore, the developing space still remains enomornous and needs more investigations to be perfect.Based on the ananasis above, we are dedicated to improve the performance of ZnO based PECC type UV detectors. Compared to the ZnO films, the ZnO nanowires (NWs) have high aspect ratio and a large surface area, enable an efficient path for electron transfer. Heryby, this thesis describes the hydrothermal method to grow ZnO NWs with high crystal quality, followed by an assembling step of the PECC UV detector. The detecting performance of which has already increased compared with other’s work, however, still poor. Therefore, this thesis further discussed the efficient methods to improve the performance of devices. Deriving from the benefit of the localized surface plasmon resonance (LSPR), we used the siver and gold nanoparticles to enhance the detecting ablitity of our devices.Wearable devices have become a hot topic recently. Howerver, due to the poor crystallinity of ZnO grown on the polymer substrates, no one has reported the flexible PECC type UV detector based on ZnO NWs.In this thesis, we introduced a method to grow ZnO NWs on flexible substrates (PET substrates) and the flexible ZnO NWs based PECC type UV detector was first fabricated, which indicates the possibility of the wearable PECC type UV detecors.