Thin film electroluminescent (TFEL) displays are attractive because they are light, have low power consumption, wide viewing angle and long lifetime, are extremely rugged and can be used in hostile environments. Recently, there has been a renewed interest in thin film electroluminescent devices because of their promising application to head mounted displays for use in automobiles, aircraft, microsurgery and virtual reality applications. Both conventional and inverted thin film electroluminescent device structures consist of insulating film, transparent conducting film and luminescent layer. In a thin film electroluminescent device, the luminescent layer is sandwiched between two insulating layers. Electrodes outside both insulating layers are used to apply an electric field, with one electrode being transparent. These thin films are found to be sensitive to preparation conditions and can be prepared by a variety of methods, such as, magnetron sputtering, chemical vapour deposition, reactive electron beam evaporation, reactive thermal deposition, spray pyrolysis, laser ablation and more recently by sol-gel process. Nowadays, the sol-gel process is a wellaccepted technology for the preparation of thin films, monoliths, fibers and monosized powders. Compared to conventional thin film forming processes such as CVD, evaporation or sputtering, sol-gel film formation requires considerably less equipment and is potentially less expensive; however the most important advantage of sol-gel processing over conventional coating methods is the ability to control precisely the microstructure of the deposited film, i.e., the pore volume, pore size and surface area. The sol-gel process is a method where the substrate to be coated is dipped into a liquid solution containing the active material. When the substrate is removed from the solution a thin layer remains. On exposure to the atmosphere a hydrolysis reaction takes place which solidifies the liquid film. In this work, all the thin films have been prepared by using sol-gel process. Insulating films of titanium dioxide and tantalum oxide were prepared from titanium and tantalum alkoxides respectively and their characteristics have been investigated. The most important requirements for the insulating layers are high dielectric constant and high electric field strength. The dielectric constants of the films were calculated from the maximum capacitance of the Al/film/Si structure. The maximum dielectric constants for Ti02 and Ta20 5 films were approximately 50 and 82 respectively annealed at 700°C in oxygen. These results suggest that the Ti02 and Ta2Os thin film can be used as a high dielectric constant insulating layer in thin film electroluminescent devices. Highly conductive and transparent aluminum-doped zinc oxide thin films have been prepared from the solution of zinc acetate and aluminum nitrate in ethanol by the sol-gel process. The effect of changing the aluminum-to-zinc ratio from 0 to 5 at. % and annealing temperature from 0 to 700°C in air, oxygen and nitrogen has been investigated. The resistivities of thin films were measured as a function of annealing temperature and also as a function of aluminum dopant concentration in the solution. As-deposited films have high resistivity and high optical transmission. Annealing of the as-deposited films in atmosphere leads to a substantial reduction in resistivity. The films have a minimum value of resistivity of 1.3xl0'4 Q-cm for 0.8 at. % aluminum-doped zinc oxide annealed at 500°C in nitrogen and a maximum transmission of about 88% when deposited on glass substrates. X-ray diffraction measurements employing CuKa radiation were performed to determine the crystallinity of the ZnO:Al films which showed that the films were polycrystalline with a hexagonal structure when annealed at higher temperatures in air, oxygen and nitrogen. Transparent conductive indium tin oxide (ITO) thin films have been prepared by a solgel process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. 0-20 % by weight Sn-doped indium oxide (ITO) films were prepared by heat-treatment at above 400°C. The electrical, optical and structural properties of ITO thin films were investigated. The electrical resistivity was measured by using four-point probe method. The ITO thin films containing 10 wt.% Sn showed the minimum resistivity of p = 8.0xl0'4 Q-cm annealed at 500°C in nitrogen. The films have an optical transparency up to 89% at 900 nm. X-ray diffraction measurements employing CuKa radiation were performed to determine the crystallinity of the ITO films which showed that the ITO films were polycrystalline with a cubic bixbyite structure annealed in air, oxygen and nitrogen. Aluminum doped zinc oxide thin films have been deposited on titanium dioxide and tantalum oxide films on glass by sol-gel process. The resistivity of ZnO:Al thin films deposited on titanium dioxide and tantalum oxide films on glass have a minimum value of 2.5xl0'3 Q-cm and 9.6xl0'4 Q-cm respectively annealed at 500°C in nitrogen. ZnO:Al thin films deposited on titanium dioxide film on glass have a higher resistivity than that deposited on glass. This increase in resistivity on titanium dioxide film is due to the diffusion of titanium into the zinc oxide layer. Indium tin oxide thin films have been deposited on titanium dioxide and tantalum oxide films on glass for thin film electroluminescent devices. The resistivity of ITO films deposited on titanium dioxide and tantalum oxide films has a minimum value of 9.5x1 O'4 Q-cm and 9.0x10'4 Q-cm respectively annealed at 500°C in nitrogen which are as low as the resistivity of ITO films deposited on glass. This combination of transparent conductive ITO thin films and titanium dioxide or tantalum oxide insulating layer can be used for thin film electroluminescent devices.