| Sumario: | Phosphors are the materials that currently drive solid-state lighting (SSL). These photoluminescent materials act as color converters, converting light generated by blue or ultraviolet LEDs to lower energy light within the visible spectrum. This group of materials, consisting of inorganic matrices doped with rare earth cations, has a wide range of applications beyond SSL due to their physicochemical properties in terms of conversion efficiency, chemical stability, and thermal stability. Examples of fields where controlled emission of these phosphors is key include horticulture, sens-ing, bioimaging, theranostics, anti-counterfeiting, and any application that requires precise control over the chromatic content of the emission and the manner in which it is extracted from the system to maximize its potential. This increase in applica-tions comes with higher demands on the materials, requiring them to meet stricter performance criteria. Some of these requirements relate to the miniaturization of optical components, where traditional materials are constrained by their micrometer scale. Furthermore, the tools and techniques used to achieve precise control over the properties of these materials are becoming increasingly sophisticated. This thesis focuses on a nanometric version of phosphors (<50nm) that are syn-thesized as colloidally stable nanoparticles and can be processed by wet methods. The work addresses the fabrication of photonic structures with these nanoparticles to modify their emission properties. From a processing point of view, three novel techniques are covered. First, thermal treatment using ultrafast annealing methods is studied, which significantly reduces the time required to fabricate films with very high conversion efficiency (>80%) and high transparency, allowing their subsequent combination with a photonic system based on periodic arrays of metallic nanopar-ticles. Second, for the first time, soft lithography is applied directly to phosphor nanoparticles to obtain monolithic structures with periodic surface patterns. Finally, inks are formulated to create arbitrary patterns with phosphors using inkjet printing, which is also compatible with soft lithography. By modifying the optical environment of the emitting nanoparticles at the nanoscale, a high degree of control over the emitted light in terms of color, direction, and intensity is achieved. It is worth noting that the thesis advances the scalability of the processes thanks to the developed methodology, which has allowed the reduction of material us-age through techniques such as inkjet printing and significant time savings through thermal processing methods, while maintaining important optical properties such as transparency and efficiency. Finally, although the results are focused on specific types of nanophosphors that exhibit down-shifting, some of the results can be applied to other inorganic nanoparticles, such as those with up-conversion. The thesis also includes a study of the properties of oxyfluoride upconversion nanoparticle films and how to optimize their emitting properties through the interconnection between thermal processing, structural properties, and their photophysical properties, with potential for integration with photonic systems. In summary, we succeeded to demonstrate the development and integration of nanophosphors into photonic structures, enabling precise control over light emis-sion properties, which has significant implications for their use in novel technologies.
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