Study On Preparation And Thermal Property Of Nano Titanium Oxide Thin Film

As one of the important components of thin film solar cells,Nano TiO₂ thin films are widely used in dye-sensitized solar cells in order to adsorb monolayer dye and separate charge.The efficiency of heat radiation of TiO₂ thin films can directly affect the photoelectric conversion efficiency of solar cells because of the important position of TiO₂ thin films in thin film solar cells.In this paper,Nano TiO₂ thin films were prepared by sol-gel method and the influence of the preparation conditions on the thermal conductivity of TiO₂ films in the direction of parallel film surface and vertical film surface was investigated by the transient electrothermal technique and the transient plane heat source method.In this experiment,four butyl titanate and isopropyl alcohol are used as raw materials and the volume ratio are 2%?3%?4%?6%?8%?10%,respectively.Two methods of film forming dip coating method and spin coating method were used to prepare TiO₂ precursor films on glass substrates with diameter of 9.17?m and glass substrates with diameter of 30mm.Then the TiO₂ films was obtained after heat treatment.The thermal diffusivities of the TiO₂ films along the film direction in different precursor concentration,annealing temperature and annealing time were measured by transient electrothermal technique,and the corresponding thermal conductivities were derived.The results show that:in the same conditions,when the four butyl titanate and isopropyl alcohol volume ratio is in the range of 2%-10%,the thermal conductivity of TiO₂ thin film in plane direction increases with the increase of the volume ratio of precursor solution;when the annealing time is in the range of 30min-180min,the thermal conductivity of TiO₂ thin film in plane direction increases with increase of the annealing time;when the annealing temperature is in the range of 60^°C-210^°C,with the increase of annealing temperature,the thermal conductivity of TiO₂ thin film in plane direction showed increased and then decreased and the critical temperature is 120^°C.The possible reasons for this phenomenon were analyzed.The thermal conductivity of TiO₂ thin film along vertical direction were measured by the improved transient plane source method.The conclusion indicate that:under the same conditions,the thermal conductivity of TiO₂ thin films in the vertical direction increases with the thickness,as well as the annealing time;when the annealing temperature is in the range of 60^°C-210^°C,the thermal conductivity of Ti O₂ thin film in the vertical direction showed increased and then decreased with the increase of annealing temperature,the optimal annealing temperature was determined to be 120^°C.The change of the thermal conductivity of TiO₂ thin film in the vertical direction showed the same trend with the thermal conductivity in parallel direction.