Novel Synthesis of the TiO₂(B) Multilayer Templated Films

TiO2(B) mesoporous thin films were grown in two steps on the F-doped SnO2 conductive glass substrates. In the first step, a small amount of H3PO4, corresponding to 0.15−0.375 wt % P on TiO2 basis, was introduced into concentrated HCl which was subsequently used for hydrolysis of titanium ethoxide. The hydrolyzed colloidal TiO2 suspension was further mixed with a 1-butanol solution of the amphiphilic triblock copolymer Pluronic P123. The obtained precursor mixture was used for dip coating of FTO substrates. To achieve over 1 μm thick films, dip coating (followed by a thermal treatment at 350 °C/2 h) was repeated several times to produce multilayer films. The films consisted of amorphous TiO2 with small amounts of anatase and TiO2(B). The amorphous part was converted into the TiO2(B) in a simple firing step at 500−550 °C. The formation of TiO2(B) phase was accompanied by a significant increase of the film thickness. The films demonstrated unique behavior during the electrochemical lithium insertion that would qualify them for fast battery or electrochromic smart window applications. The efficiency of multiphase TiO2 films in dye sensitized solar cells depends on the composition of individual films: it increases in the series: anatase/amorphous TiO2 < anatase/TiO2(B) < anatase.