'Sol-Gel Synthesis and Characterization of TiO2 and TiO2-V2O5 Films for Electrodes in Asymmetric Liquid Crystal Cells

Titania and titania/vanadia thin films were prepared via solgel process, starting from alcoholic solution of Ti (OBu)4 for pure titania films and from Ti (OBu)4/VO(OPri)3 for mixed oxide films. The main requirements of these materials for applications in electrochromic devices were investigated, i.e. high charge capacity and electrochemical stability. Microstructural and electrochemical characterizations were carried out both on gels and films leading to the following results: titania films showed a high electro-chemical stability associated with a good charge capacity, whereas mixed oxide systems displayed a high stability again but a lower intercalation/deintercalation charges. The first electro-optic measurements were also performed for two films with different Ti:V atomic ratio, to check the interaction with liquid crystals in modified nematic liquid crystal cells: the cell containing films poorer in vanadia give some rectification effect, but they have a very complex dependence on the applied potential and very slow relaxation times; on the contrary films richer in vanadia exhibits very good response in the liquid crystal cells, compared with another mixed conductivity oxides. © 2001 Taylor and Francis, Inc.