Maria Alcaire

Soft plasma processing of organic nanowires: a route for the fabrication of 1D organic heterostructures and the template synthesis of inorganic 1D nanostructures

Hierarchical (branched) and hybrid metal-NPs/organic supported NWs are fabricated through controlled plasma processing of metalloporphyrin, metallophthalocyanine and perylene nanowires. The procedure is also applied for the development of a general template route for the synthesis of supported metal and metal oxide nanowires.

Bending induced self-organized switchable gratings on polymeric substrates

We present a straightforward procedure of self-surface patterning with potential applications as large area gratings, invisible labeling, optomechanical transducers, or smart windows. The methodology is based in the formation of parallel micrometric crack patterns when polydimethylsiloxane foils coated with tilted nanocolumnar SiO2 thin films are manually bent. The SiO2 thin films are grown by glancing angle deposition at room temperature. The results indicate that crack spacing is controlled by the film nanostructure independently of the film thickness and bending curvature. They also show that the in-plane microstructural anisotropy of the SiO2 films due to column association perpendicular to the growth direction determines the anisotropic formation of parallel cracks along two main axes. These self-organized patterned foils are completely transparent and work as customized reversible diffraction gratings under mechanical activation.

Luminescent 3-hydroxyflavone nanocomposites with a tuneable refractive index for photonics and UV detection by plasma assisted vacuum deposition

Luminescent organic-thin-films transparent in the visible region have been synthesized by a plasma assisted vacuum deposition method. The films have been developed for their implementation in photonic devices and for UV detection. They consist of a plasma polymeric matrix that incorporates 3-hydroxyflavone molecules characterized by absorption of UV radiation and emission of green light. The present work studies in detail the properties and synthesis of this kind of transparent and luminescent material. The samples were characterized by X-ray photoemission (XPS), infrared (FT-IR) and secondary ion mass (ToF-SIMS) spectroscopies; and their optical properties were analysed by UV-Vis absorption, fluorescence and ellipsometry (VASE) spectroscopies. The key factors controlling the optical and luminescent properties of the films are also discussed. Indeed, our experimental results show how the optical properties of the films can be adjusted for their integration in photonic devices. Moreover, time resolved and steady state fluorescence analyses, including quantum yield determination, indicate that the fluorescence efficiency is a function of the deposition parameters. An outstanding property of these materials is that, even for high UV absorption values (i.e. large layer thickness and/or dye concentration), the emitted light is not reabsorbed by the film. Such highly UV absorbent and green emitting films can be used as UV photodetectors with a detection threshold smaller than 10 μW cm−2, a value similar to the limit of some commercial UV photodetectors. Based on these properties, the use of the films as visual tags for the detection of solar UV irradiation is proposed.

Enhancing Moisture and Water Resistance in Perovskite Solar Cells by Encapsulation with Ultrathin Plasma Polymers

A compromise between high power conversion efficiency and long-term stability of hybrid organic-inorganic metal halide perovskite solar cells is necessary for their outdoor photovoltaic application and commercialization. Herein, a method to improve the stability of perovskite solar cells under water and moisture exposure consisting of the encapsulation of the cell with an ultrathin plasma polymer is reported. The deposition of the polymer is carried out at room temperature by the remote plasma vacuum deposition of adamantane powder. This encapsulation method does not affect the photovoltaic performance of the tested devices and is virtually compatible with any device configuration independent of the chemical composition. After 30 days under ambient conditions with a relative humidity (RH) in the range of 35-60%, the absorbance of encapsulated perovskite films remains practically unaltered. The deterioration in the photovoltaic performance of the corresponding encapsulated devices also becomes significantly delayed with respect to devices without encapsulation when vented continuously with very humid air (RH > 85%). More impressively, when encapsulated solar devices were immersed in liquid water, the photovoltaic performance was not affected at least within the first 60 s. In fact, it has been possible to measure the power conversion efficiency of encapsulated devices under operation in water. The proposed method opens up a new promising strategy to develop stable photovoltaic and photocatalytic perovskite devices.