Study On Electro-optical Properties Of VO₂/FTO Composite Films

The ‘Smart Window’ could according to the external environment temperature change that changed of infrared transmittance of the window, so as to achieve the effect of energy conservation and environmental protection. On intelligent window material selection, VO2 thin films materials attracted the attention of many people for the thermochromism characteristics. Before and after the phase transition temperature, VO2 thin films material structure and photoelectric properties would have a huge change, and this change was reversible.Through the multi-layer Matrix calculation theory, modified Sellmeier dispersion model and the theory of the classical Preisach model. The paper respectively set up VO2/FTO composite films optical model and the new theory of Preisach model. Based on these two kinds of model, calculation and analysis of the optical properties and electrical properties for VO2/FTO composite films, and compared with the composite films’ optoelectronic properties that prepared by magnetron sputtering, the results showed that the results were consistent. Study showed that as VO2/FTO composite films thickness increases, the transmittance decreases, thermal hysteresis loop width, phase transition temperature decreases, these were mainly affected by crystalline of composite films.Then, at room temperature using the method of magnetron sputtering on conductive glass substrate FTO which was plated a layer of vanadium metal, then make the metal vanadium into VO2 thin films through annealing process to obtain the VO2/ FTO composite film, also studied and analyzed the influence of some process parameters with the composite films’ characteristics, for improving the technological process of preparation of VO2/FTO composite films, to obtain the optimum process parameters.Finally, the structure, optical properties and electrical characteristics of the VO2/FTO composite films were analyzed by instruments. Results show that FTO on the conductive glass does not change the preferred orientation growth of VO2 thin films, but significantly change its surface morphology characteristics. Compared with the VO2 thin films that were prepared on glass substrates with the same process conditions, the phase transition temperature of the VO2/FTO composite films is decreased about 18℃, the width of thermal hysteresis is narrowed by about 4℃, and the infrared transmittances before and after phase transition are 42% and 21% respectively. It suggested that the composite films can reduce the phase transition temperature and limit the thermal hysteresis loop as well as enhance the infrared light modulation capabilities of VO2 thin films.