Nano-TiO₂ Thin Film Prepared By Colloidal Spray Coating And Its Application In Dye Sensitized Solar Cells

Dye-sensitized solar cell (DSSC) is a new type of solar cell with the advantages of low cost, simple preparation process and friendly environment, compared with the solar cells of semiconductor silicon and compound. In recent years, the DSSC, with a good promise in application, is attraction much attention internationally and is developing rapidlyThe TiO₂ thin film is one of the key components of a DSSC. The film plays a role in fixing dyes, accepting the injecting electrons that produced by dyes and transfering them to the ITO conductive glass surfaces. The structure of TiO₂ thin film has a significant impact on the photoelectricity properties of a DSSC. A crack-free film with high surface area, appropriate pore size and thickness can effectively increase the power of DSSC. The main research content of this paper as follows:(1) Nano-TiO₂ thin film was prepared using TiO₂ (P25) powder by colloidal spray coating and it was used to make a dye sensitized solar cell (DSSC). The DSSC was tested in the standard simulation sunlight (AM1.5G). The short-current density is 7.78mA/cm2 and the photoelectric conversion efficiency reaches 1.94%. The microstructure of TiO₂ thin films was characterized and analyzed with SEM and it was found that the TiO₂ film was homogeneous, porous, the size of TiO₂ granule is 20-30nm, and the thickness of the film can be well controlled at 5 to 20μm. Studies have shown that the properties of TiO₂ thin films were affected by the content of terpineol dispersant and ethyl cellulose binder used in the preparation.(2) Preparation of TiO₂ thin films using TiO₂ powder with doctor blade process and it was used to assemble a dye sensitized solar cell (DSSC). The results show that the properties of TiO₂ thin films prepared by colloidal spray coating are better than those by doctor blade process.(3) With ethanol or triethanolamine as solvent, polyvinyl butyral as binder, and polyethylene glycol(1000) as pore-former, the TiO₂ thin films were prepared by colloidal spray coating. The effects of the above additional materials on the performance of the films were studied. The structure of films were characterized by SEM. The photoelectricity properties of the DSSCs with the films as prepared were tested, and the data were summarized and analyzed. It was found that the type and proportion of additives influences the performance of solar cells greatly. In conclusion, based on existing data, the direction of efforts to optimize the preparation process of the TiO₂ thin films have been proposed.(4) Four well-structured porous TiO₂ films made by colloidal spray coating, with different coating times, having different thickness. It is found that the method can control the thickness of the film easily with different spraying times. In a word, the colloidal spray coating is a good technique for making TiO₂ thin films for DSSCs.