Research On The Preparation Of Gallium Heavily Doped ZnO Nano-crystals And Films For Energy-efficient Coating Windows

With the development of energy saving, higher requirements for smartwindow of bulidings have been proposed. Due to high transmittance in the visibleregion and high reflectivity in the near infrared region, TCO （transparentconductive oxide） films have many advantages for energy-efficient coatingwindow applications. Compared with commonly used ITO films, zinc oxide isabundant and environmental friendly. Moreover, the size of gallium atom is veryclose to that of zinc atom, gallium-doped zinc oxide (GZO), especially for itsnano-crystal with high doping concentration, GZO nano-crystal or film has highercarrier concentration, which can be achieved easily for shorter infraredtransmission cutoff wavelength and higher infrared reflectivity. In this paper,which focused on the study of the prepration of GZO nano-crystals and films.Firstly, GZO films with different doping levels have been prepared bydouble-target magnetron sputtering. Meanwhile, GZO nano-crystals have beenobtained in high-temperature nonaqueous solutions, and subsquent films havebeen obtained by spin-coating. Finally, the GZO films prepared by those twomethods have been studied for the application in energy-efficient coatingwindows.The experiment results of sputtering GZO films using Zn and Ga2O3doubletargets show that the as-sputtered GZO films have hexagonal wurtzite structurepreferentially oriented in the (002) crystallographic direction. XPS and XRDindicate that the films have achieved effective doping, in which the maximumdoping amount of Ga is6.56.at.%. The maximum average transmittance ofas-grown films reachs89%in the visible spectrum region (380~800nm). Theannealing in a reducing atmosphere can improve the crystal quality and opticalproperty, the maximum average transmittance of annealed films is91%in thevisible region. The visible-NIR transmission result show there is a―blue shift‖forthe absorption edge of film in the near infrared region with increasing Ga2O3sputtering power. The transmittance of GZO film is less than7%in thenear-infrared spectrum region (1700~2500nm).The experiments results of the preparation of GZO nanocrystals in high-temperature nonaqueous solution show that the mechanism is esterificationreaction, and the impurities in the solution can be effectively cleaned by organicsolvent. The microstructure of the as-obtained ZnO nanoparticles is consistentwith wurtzite. The experimental parameters such as reaction temperature, holdingtime, the content of1,2-dodecanediol and oleic acid all have significant influenceson the morphologies and optical properties of ZnO nano-crystals. XRD and EDSanalyses showed that it has achieved for effective doping with gallium in ZnOnano-crystal. TEM shows that the mean diameter of GZO nanoparticles is about5nm. With the increase of the content of gallium acetylacetonate, FTIR analysisshowed that absorption intensity of GZO nanoparticles in the NIR region havegradually increased and there is a―blue shift‖for IR absorption edge. Thesubsquent GZO films can be prepared by spin-coating. It has been studied for theinfluences of the film thickness and composition on the structure and properties ofas-obtained GZO films. The GZO films prepared by spin-coating GZOnanocrystals, have shown their good application prospects for the energy-efficientcoating window.