Silver (Ag) and tin (Sn) nanoparticles (NPs) were deposited by thermal evaporation onto heated glass substrates with a good control of size, shape and surface coverage. This process has the advantage of allowing the fabrication of thin-film solar cells with incorporated NPs without vacuum break, since it does not require chemical processes or post-deposition annealing. The X-ray diffraction, TEM and SEM properties are correlated with optical measurements and amorphous silicon hydrogenated (a-Si:H) films deposited on top of both types of NPs show enhanced absorbance in the near-infrared. The results are interpreted with electromagnetic modelling performed with Mie theory. A broad emission in the near-infrared region is considerably increased after covering the Ag nanoparticles with an a-Si:H layer. Such effect may be of interest for possible down-conversion mechanisms in novel photovoltaic devices.

The intense light scattered from metal nanoparticles sustaining surface plasmons makes them attractive for light trapping in photovoltaic applications. However, a strong resonant response from nanoparticle ensembles can only be obtained if the particles have monodisperse physical properties. Presently, the chemical synthesis of colloidal nanoparticles is the method that produces the highest monodispersion in geometry and material quality, with the added benefits of being low-temperature, low-cost, easily scalable and of allowing control of the surface coverage of the deposited particles. In this paper, novel plasmonic back-reflector structures were developed using spherical gold colloids with appropriate dimensions for pronounced far-field scattering. The plasmonic back reflectors are incorporated in the rear contact of thin film n-i-p nanocrystalline silicon solar cells to boost their photocurrent generation via optical path length enhancement inside the silicon layer. The quantum efficiency spectra of the devices revealed a remarkable broadband enhancement, resulting from both light scattering from the metal nanoparticles and improved light incoupling caused by the hemispherical corrugations at the cells' front surface formed from the deposition of material over the spherically shaped colloids.

Plasmonic light trapping in thin film silicon solar cells is a promising route to achieve high efficiency with reduced volumes of semiconductor material. In this paper, we study the enhancement in the opto-electronic performance of thin a-Si:H solar cells due to the light scattering effects of plasmonic back reflectors (PBRs), composed of self-assembled silver nanoparticles (NPs), incorporated on the cells’ rear contact. The optical properties of the PBRs are investigated according to the morphology of the NPs, which can be tuned by the fabrication parameters. By analyzing sets of solar cells built on distinct PBRs we show that the photocurrent enhancement achieved in the a-Si:H light trapping window (600 – 800 nm) stays in linear relation with the PBRs diffuse reflection. The best-performing PBRs allow a pronounced broadband photocurrent enhancement in the cells which is attributed not only to the plasmon-assisted light scattering from the NPs but also to the front surface texture originated from the conformal growth of the cell material over the particles. As a result, remarkably high values of Jsc and Voc are achieved in comparison to those previously reported in the literature for the same type of devices.

The color sensing ability of a data acquisition prototype system integrating a 32 linear array of 1D amorphous silicon position sensitive detectors (PSD) was analyzed. Besides being used to reproduce a 3D profile of highly reflective surfaces, here we show that it can also differentiate primary red, green, blue (RGB) and derived colors. This was realized by using an incident beam with a RGB color combination and adequate integration times taking into account that a color surface mostly reflects its corresponding color. A mean colorimetric error of 25.7 was obtained. Overall, we show that color detection is possible via the use of this sensor array system, composed by a simpler amorphous silicon pin junction.

Developments in thermoelectric (TE) transparent p-type materials are scarce and do not follow the trend of the corresponding n-type materials – a limitation of the current transparent thermoelectric devices. P-type thermoelectric thin films of CuI have been developed by three different methods in order to maximise optical transparency (>70% in the visible range), electrical (σ = 1.1 × 104 Sm−1) and thermoelectric properties (ZT = 0.22 at 300 K). These have been applied in the first planar fully transparent p-n type TE modules where gallium-doped zinc oxide (GZO) thin films were used as the n-type element and indium thin oxide (ITO) thin films as electrodes. A thorough study of power output in single elements and p-n modules electrically connected in series and thermally connected in parallel is inclosed. This configuration allows for a whole range of highly transparent thermoelectric applications.

The interaction of light with wavelength-sized photonic nanostructures is highly promising for light management applied to thin-film photovoltaics. Several light trapping effects come into play in the wave optics regime of such structures that crucially depend on the parameters of the photonic and absorbing elements. Thus, multi-parameter optimizations employing exact numerical models, as performed in this work, are essential to determine the maximum photocurrent enhancement that can be produced in solar cells.

Generalized spheroidal geometries and high-index dielectric materials are considered here to model the design of the optical elements providing broadband absorption enhancement in planar silicon solar cells. The physical mechanisms responsible for such enhancement are schematized in a spectral diagram, providing a deeper understanding of the advantageous characteristics of the optimized geometries. The best structures, composed of TiO2 half-spheroids patterned on the cells' top surface, yield two times higher photocurrent (up to 32.5 mA/cm2 in 1.5 µm thick silicon layer) than the same devices without photonic schemes.

These results set the state-of-the-art closer to the theoretical Lambertian limit. In addition, the considered light trapping designs are not affected by the traditional compromise between absorption enhancement versus current degradation by recombination, which is a key technological advantage.

Microporous materials highly activated and with potential to be used as adsorbents in many applications for gas
separation/purification are usually available as powders. These solids usually have a great and reversible gas
uptake, high gas selectivity, good chemical and thermal stability, but are unsuitable to be used in gas adsorption
processes, such as Pressure Swing Adsorption (PSA) or Simulated Moving Bed (SMB).
Zeolites, carbons and more recently metal-organic frameworks (MOFs) are examples of those materials. Their
use in adsorption-based processes are dependent of their upgrading from powders (micrometer scale) to
particles (pellets, spheres or granules at millimeter scale). This would overcome large pressure drops and
consequent energy consumptions when packing adsorbent columns in those processes. Thus, shaping
adsorbents is an important step to use them in industry, although it greatly affects their capacity and selectivity
towards a specific gas separation.
In this work, we explore techniques to shape powdered adsorbents, followed by their textural and mechanical
characterizations, and the study of their adsorption properties towards the main components of post-combustion
flues gases (CO2 and N2). Materials densification is proposed by employing two approaches:
- Conventional shaping through binderless mechanical compression and binder-containing extrusion; and
- Formulation by 3D printing (or additive manufacturing) to produce packed bed morphologies that
precisely replicate computer aided design (CAD) models.
Porous separation media are important for fluid-solid contacting in many unit operations, including adsorption.
Due to practical limitations, media particles are typically packed randomly into a column in a shaped form,
allowing fluid to flow through the interstitial voids. Key to the effectiveness of packed columns are the flowrelated properties of mass transfer, fluid distribution and dispersion, and back pressure, which in turn depend
upon packing geometry. Until now, no alternative was found to overcome this limitation and have optimal
ordered packing arrangements at the micron scale. 3D-Printing (or additive manufacturing) brings a wide range
of benefits that traditional methods of manufacturing or prototyping simply cannot. With this approach, complex
ordered geometries, that are not possible by conventional extrusion, can be designed and printed for a porous
media, being the equipment resolution the only limiting step to overcome.
The effect of parameters like compression force, particle sieving, binder nature, binder/adsorbent ratio were
firstly studied using conventional shaping techniques, as a basis for the consequent development of 3D-printed
formulations. The structured samples are then characterized and adsorption equilibria studies are performed on
them to evaluate their performance as media for gas adsorption separation processes. A volumetric/manometric
adsorption unit built in-house was used for this purpose. Relevant experimental data is obtained, which allows to
conclude that 3D-printed media can be an alternative porous media for application in gas adsorption processes.

The influence of Ag nanoparticles (Ag NPs) on the luminescence of electrospun nonwoven mats made of polyvinylpyrrolidone (PVP) has been studied in this work. The PVP fibers incorporating 2.1–4.3 nm size Ag NPs show a significant photoluminescence (PL) band between 580 and 640 nm under 325 nm laser excitation. The down conversion luminescence emission is present even after several hours of laser excitation, which denotes the durability and stability of fibers to consecutive excitations. As so these one-dimensional photonic fibers made using cheap methods is of great importance for organic optoelectronic applications, fluorescent clothing or counterfeiting labels.