Facile synthesis and characterization of Al-Doped ZnO Nanostructures and Their Applications in Sensors and Solar Cells

Abstract

In recent years many zinc oxide (ZnO) nanostructures with one-dimensional (1D) and two-dimensional (2D) morphologies such as nanorods nanobelts nanowalls and nanoflowers have attracted much attention for their potential use as fundamental building blocks for new generation of electronic and photonic devices In this study ZnO nanostructure (including nanorods nanowall nanoflower and hybrid nanostructures) were fabricated with chemical bath method at low temperature Firstly we developed a hydrothermal method for the growth of three types of ZnO nanostructures: nanorods nanowalls and nanoflowers The structures are produced at high densities with a high degree of uniformity on Al-coated SiO2 substrates without the need for surfactant The proposed method makes it possible to control the distribution of these structures along the grooves created by altering the growth rate of ZnO nanorods and nanowalls Secondly we report on a means of tuning the morphology of ZnO nanostructure using Al thin film as a doping source An increase in the thickness of the Al thin film causes the evolution of the morphology from nanorods to nanowalls We managed to produce AZO nanostructures with higher doping concentrations (9 at%) by using various thicknesses of Al film as a reaction layer The resulting photosensor was tested using a 405 nm light-emitting diode (LED) at a voltage bias of 1 V across the device wherein a photocurrent-to-dark-current ratio of 99 5 was observed Thirdly we fabricated an overlapping structure of vertical nanorods and nanowalls using a chemical bath method The proposed multilayer Al/ZnO/Al/ZnO buffer results in the formation of two types of nanostructure (nanowalls and rods) and also increased the length to which the nanorods grow over time In addition a cholesterol biosensor was constructed using these nanostructures as supporting materials for cholesterol oxidase loading The device achieved sensitivity of 93 82 μA/mMcm2 within a linear-range of 50–500 mgdl-1 Final a hybrid nanostructure comprising ZnO nanorods embedded in polymethylmethacrylate (PMMA) was developed for use as an antireflection (AR) coating The ZnO nanorod/PMMA structure that underwent O2 plasma treatment for 120s presented the highest efficiency of 11 57 % In addition reports on the fabrication of ZnO nanowalls for use as an electron collecting layer (ECL) in CH3NH3PbI3 perovskite solar cells (PSCs) The proposed ZnO nanowalls achieved a ?ll factor signi?cantly higher than that of ZnO thin ?lms which translated into a remarkable improvement in power conversion ef?ciency reaching 13 6 % under AM 1 5G illumination

Date of Award	2017 Feb 7
Original language	English
Supervisor	Sheng-Yuan Chu (Supervisor)