Studies On The Fabrication And Optoelectric Properties Of Transparent Conductive Films Based On Silver Nanowires And Metal Oxide Composites

Transparent electrode is an important part of the solar cells, screen displays and portable electronics with broad prospects. Traditional ITO and FTO cannot meet the needs of the industry with the development of organic and flexible electronics, seeking for the alternative materials has become a hot topic in the field of transparent conductive film. Among alternative materials, random silver nanowire(Ag NW) networks show the excellent electrical conductivity, permeability and wide spectrum ductility and are regarded as the leading candidates. However, bare metal nanowires are vulnerable in the environment and have poor adhesion to substrates, which hinders their integration into photoelectric devices. In addition, amorphous alloy oxide materials such as indium zinc oxide(IZO) not only have the adjustable electrical parameters, but also present good stability and outstanding mechanical robustness when bent. However, all these are existing owing the lack of completely understanding to amorphous oxide materials, still need to conduct in-depth researches from theoretical and experimental aspects.In this thesis, we exert their respective superiorities of Ag NW networks and amorphous oxide materials to construct the Ag NWs/metal oxide composite films. We establish the dependencies between photolelctric properties and structural transformations, and also study the optoelectric properties of amorphous IZO films by the physical deposition and the interaction characteristics between networks and the incident wavelength. The main results are as follows:1. First, the amorphous and polycrystalline IZO thin films were grown by PLD technique in oxygen and argon atmosphere. The evolution of surface morphology and crystalline structure of the IZO films have been discussed in the frame of the kinetic molecular theory by considering the different kinetic energy loss and the surface migration of impinging particles in Ar and O2 atmosphere, respectively. Hall measurements show that for amorphous IZO films the highest electron mobility can be obtained under O2 atmosphere. By theoretical fitting the data and subsequent variable-temperature experiments, it is found that different scattering mechanisms will control the dependence of μ on Ne. The linear portion of Eopt vs. Ne2/3 is attributed to the Burstein-Moss shift and the rapid decrease of Eopt is attributed to the band-gap renormalization, which provides an opportunity for tuning the band gaps of IZO films.2. Subsequently, we proposed a composite structure employing a network of Ag NWs and a sol-gel IZO for realizing high performance transparent conductors. By involving IZO nanoparticles into the network of Ag NWs, the sheet resistance was dramatically decreased without sacrificing the transparency. Meanwhile our composite structure shows excellent stability upon oxidation test and mechanical adhesion against tape test. We studied the electrical properties of composite films under the different output current and test temperature. The inorganic IZO can acts as a protective and adhesive layer, also this conductive material provides the additional conductive pathways into the network of Ag NWs. The electron transport properties of the Ag NWs/IZO regime were in accordance with the thermionic emission theory according to the test of I-V curve and the exponential curve fit of the experimental data. And we obtained the quantitative formula of the I-V characteristics for the composite structure.3. We proposed the atomic layer deposition of AZO for the smaller size Ag NWs to achieve low-temperature processed indium-free Ag NWs/AZO composite transparent electrodes. The figure-of-merit of composite transparent electrode was evaluated through the different calculation methods including the Haacke formula and percolation theory. Furthermore, the composite electrode has been demonstrated to enhance the EL intensity due to the improvement of electrons injection efficiency and the resonant coupling between Zn O excitons and Ag NWs’ LSP. Unlike conventional oxide film, the Ag NW network structure also served as the antireflective coating to enlarge the spatial distribution of the light emission from LEDs.