Preparation Of Dye-sensitized Solar Cells Photoelectrode TiO₂ Porous Film By Reverse Microemulsion Method

Dye-sensitized solar cell (DSC) is a new type of the photoelectrochemical solar cell. It has attracted great attention because of its low-cost, simple fabrication procedure and environment friendly compared to semiconductor solar cell. Dye-sensitized TiO₂ porous film photoelectrode is the key part of this kind of solar cell. The researchers have reported several methods to fabricate the TiO₂ porous film, such as: the sol-gel method, the hydrothermal synthesis, the power-coating method, the electrochemical deposition method, and so on. But these methods mostly have two disadvantages:(1)It is difficult to avoid the aggregation of Nanoparticles to obtain high dispersed TiO₂ Nanoparticles (2)It is difficult to obtain high crystallinity anatase TiO₂ Nanoparticles.So it is significant to research a method that can obtain high dispersed TiO₂ Nanoparticles with simple process,and avoid the difficulty of conventional methods to prepare high crystallinity anatase TiO₂ Nanoparticles.In this study, an amorphous TiO₂ porous film was prepared by Tetrahydrofuran modified reverse microemulsion method, and the photoelectric properties of the DSC based on the prepared amorphous TiO₂ film are researched.The reverse microemulsion formed by CTAB,n-butyl alcohol,cyclohexane and water have several important parameters to influence the preparation of TiO₂ Nanoparticles,such as the reactant concentration,micelle interfacial flexibility,the reaction temperature,the ripening time. The relations of the microstructure, photoelectric properties of amorphous TiO₂ porous films and these parameters are discussed. The modified mechanism of THF to reverse microemulsion and the relations the dosage of THF and the microstructure, photoelectric properties of amorphous TiO₂ porous films are also researched in this study. The results shows that the appropriate condition to obtain TiO₂ porous film with good microstructure and photoelectric properties is: water, cyclohexane, CTAB, n-butyl alcohol and THF is mixed with a mass ratio of 1:4:0.6:0.6:2.7-5.4 to form transparent reverse microemulsion, the mixture of tetrabutyl titanate and diethanolamine with a volume ratio of 1:1 to water, and the ripening time is 10 days. The results also shows the THF has two important functions:(1) Before the hydrolyzation, THF can be used to disperse the micelle to avoid the aggregation of the micelle (2) After the hydrolyzation, THF can disperse the hydrated TiO₂ particles to keep proper distance to facilate the fabrication of the film, and avoid that the film tends to cracking and flaking off during sintering process owing to the bad interfacial structure between the Nanoparticles.To prove whether the amorphous TiO₂ porous films can be used to fabricate the DSC effectively, the power-coating method is used, and the slurry of commercial Titania (P25) powders (containing mainly anatase) are deposited on the substrates to obtain nanocrystalline porous films. The microstructure, photoelectric properties of the two kind films are compared. The results shows the spherical amorphous TiO₂ Nanoparticles with about an average size of 20nm size can be interconnected to form porous network just like the P25 nanocrystallines does, which provides the huge surface area and porosity and can be used to fabricate the DSC. The photoelectric efficiency of the DSC based on the prepared amorphous TiO₂ film is 4.68%, which is comparable to that of DSC based on the P25 nanocrystalline in the same testing conditions, which improves the low efficiency of the amorphous TiO₂, and prove the amorphous TiO₂ porous films can be used to fabricate the DSC effectively.