Optical Properties of Titania Coatings Prepared by Inkjet Direct Patterning of a Reverse Micelles Sol-Gel Composition

Abstract

Thin layers of titanium dioxide were fabricated by direct inkjet patterning of a reverse micelles sol-gel composition onto soda-lime glass plates. Several series of variable thickness samples were produced by repeated overprinting and these were further calcined at different temperatures. The resulting layers were inspected by optical and scanning electronic microscopy and their optical properties were investigated by spectroscopic ellipsometry in the range of 200-1000 nm. Thus the influence of the calcination temperature on material as well as optical properties of the patterned micellar titania was studied. The additive nature of the deposition process was demonstrated by a linear dependence of total thickness on the number of printed layers without being significantly affected by the calcination temperature. The micellar imprints structure of the titania layer resulted into significant deviation of measured optical constants from the values reported for bulk titania. The introduction of a void layer into the ellipsometric model was found necessary for this particular type of titania and enabled correct ellipsometric determination of layer thickness, well matching the thickness values from mechanical profilometry.

Fast and Low-Temperature (70 °C) Mineralization of Inkjet Printed Mesoporous TiO2 Photoanodes Using Ambient Air Plasma

“…Further investigation of textural changes in the actual printed layers before and after processing was performed indirectly by evaluation of SEM images and ellipsometric spectra of the inkjetprinted samples before and after plasma processing. A complex multilayer model involving a variable void layer, adapted from our previous work on the optical properties of printed pure titania films, 43 was used for the recorded spectra fitting. This facilitated a relative comparison of porosity changes upon plasma treatment.…”

Laser Annealing of TiO2 Electron-Transporting Layer in Perovskite Solar Cells

“…A summary of the data is in Figure . TiO 2 films have a refractive index peak around 300 nm between 2.0 and 3.3 and a band gap between 3.2 and 3.6 eV, which correlates positively with film phase and density. , Voids in the film have refractive indices near 1.0 and decrease the overall refractive index of the film, indicating that denser films with fewer voids will have higher index. Our unannealed films have a band gap of 3.35 eV and a peak refractive index of 1.9, which increases to E g = 3.51 eV and n peak = 2.05 after thermal annealing at 500 °C for 5 min, demonstrating an increase in film density and transition to crystalline phase.…”

Active Sites in Heterogeneous Photocatalysis: Brief Notes on the Identification of their Analogies with the Standard Heterogeneous Catalysis Concept

“…6 shows the atomic force microscopy (AFM) image of the globular structure of film A, the one originating from the micellar templating core. The film was printed by a piezoelectric jet [37,[43][44][45]. It is evident that the printed (and calcined) layer maintained the imprints of individual micelles.…”

“…Here, it must be added that layer A was produced by the sol-gel process in the templating environment of reverse micelles. It is characterized by a very smooth surface (structure), which is formed of densely packed spherical particles originating from the spherical cores of the templates (reverse micelles) [37,43,44]. Each inter-particle barrier acts as a recombination center, and film A (unlike films B, C, and D) is very rich in such barriers.…”