Because of their dense structure, electrochromic sputtered tungsten oxide thin films often show low coloration efficiency, low ion mobility, and the tendency to incorporate lithium ions irreversibly. An interesting possibility to modify the structure is the admixture of other non- absorbing metal oxides. Recent results from Japan indicate improved electrochromic behavior of evaporated WO3 - TiO2 mixed films. In order to verify this effect for different deposition techniques, we examined thin films of WO3 - TiO2 produced by the sol-gel method and dc magnetron sputtering. Both types of films were characterized optically and electrochemically in organic LiClO4 solutions. The cycling stability as a function of titania concentration was recorded. Improved electrochromic properties were found for both sputtered and sol-gel films.
Inorganic glasses prepared by the 'cold' chemical sol-gel process can present an alternative host material for
organic fluorescent dyes. We report on measurements done on thin Si02 layers prepared as sol-gels and doped
with various dyes on a glass substrate. The preparation is done by dip-coating of the substrate in the corresponding
alcoxide solutions. Good quality layers without crazing after drying are achieved with a thickness of up to 1-2
microns.
The measurements include absorption measurements (UV to IR), fluorescence and excitation measurements
(visible to NIR), and measurements of photo-decomposition. The optical properties of the dye molecules in the
layer and in the sol-gel solutions are studied as a function of dye concentration and changes in the thermal treatment
of the layers. The results are examined for their applicability to FPC's.
Further we report on small silver islands (submicron size) brought into the sol-gel solution as stabilized
colloids or by chemical reduction of Ag+ salts. According to theoretical predictions, the electromagnetic interaction
of silver surface plasmons and dye molecules can result, under certain conditions, in an enhanced
fluorescence quantum efficiency and photostability of the dye.
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