Abstract
We propose an up-scalable, reliable, contamination-free, rod-like TiO2 material grown by a new method based on sputtering deposition concepts which offers a multi-scale porosity, namely: an intra-rods nano-porosity (1–5 nm) arising from the Thornton’s conditions and an extra-rods meso-porosity (10–50 nm) originating from the spatial separation of the Titanium and Oxygen sources combined with a grazing Ti flux. The procedure is simple, since it does not require any template layer to trigger the nano-structuring, and versatile, since porosity and layer thickness can be easily tuned; it is empowered by the lack of contaminations/solvents and by the structural stability of the material (at least) up to 500 °C. Our material gains porosity, stability and infiltration capability superior if compared to conventionally sputtered TiO2 layers. Its competition level with chemically synthesized reference counterparts is doubly demonstrated: in Dye Sensitized Solar Cells, by the infiltration and chemisorption of N-719 dye (∼1 × 1020 molecules/cm3); and in Perovskite Solar Cells, by the capillary infiltration of solution processed CH3NH3PbI3 which allowed reaching efficiency of 11.7%. Based on the demonstrated attitude of the material to be functionalized, its surface activity could be differently tailored on other molecules or gas species or liquids to enlarge the range of application in different fields.
Highlights
Scheme of the photo-anode of a DSC4 or PSC18, a mesoporous thin film of nanosized TiO2 crystals is deposited on a Transparent Conductive Oxide (TCO), annealed for grains sintering and anatase crystallization, and subsequently imbued with a photoactive dye[25,26,27,28,29] or infiltrated with perovskite[30]
In this paper we propose a material with multi-scale porosity ranging from nano- to meso- dimensionalities grown by a modified sputtering method, and we demonstrate its attitude to be functionalized with species of different nature
We grow multi-porosity TiO2 scaffolds offering, in perspective, a transversal empowering over different technologies, including photovoltaics, sensors, water purification, water splitting etc
Summary
Scheme of the photo-anode of a DSC4 or PSC18, a mesoporous thin film of nanosized TiO2 crystals is deposited on a Transparent Conductive Oxide (TCO), annealed for grains sintering and anatase crystallization (typically at 500 °C), and subsequently imbued with a photoactive dye[25,26,27,28,29] or infiltrated with perovskite[30]. Some other attempts were done by GLancing Angle Deposition (GLAD)[40] to deposit Ti nanostructures[41,42,43] which requires ex-situ oxidation for TiO2 reaction; or by using array of template materials (e.g. polystyrene nano-spheres) to exploit their shadowing effect during TiO2 growth[44] They lack of process simplification and of a transversal demonstration on the applicative valence of the porous scaffold to largely and deeply infiltrate materials of different size and/or nature to be used for wide-ranging applications. In this paper we propose a material with multi-scale porosity ranging from nano- to meso- dimensionalities grown by a modified (up-scalable) sputtering method, and we demonstrate its attitude to be functionalized with species of different nature To this intent, two photoactive blends, namely TiO2+dye and TiO2+perovskite, are realised, characterised and tested in prototype DSCs and PSCs to provide a proofs-of-concept on the transversal empowering of the material
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