Periodic Reporting for period 4 - NANOPHOM (Nanophosphor-based photonic materials for next generation light-emitting devices)
Okres sprawozdawczy: 2021-10-01 do 2023-03-31
A transition towards energy-efficient and environmentally friendly light sources is an essential part of the worldwide strategy to reduce electricity consumption. Nowadays, (inorganic) LEDs use a mature technology that can outperform traditional light sources due to their low power consumption, long lifetime, fast switching, robustness, and compact size. Despite these advantages, the much-needed transition is being hampered by the limited control over color quality and directionality of LED light emission that standard materials and reflectors and lenses, typically employed as secondary optical elements, provide.
NANOPHOM seeks to surpass the limits imposed by geometrical optics in the radiation shaping of light-emitting devices by means of nanophotonics. We aim at tailoring the emission properties of nano-sources using integrated nanostructured optical components, rather than following the traditional approach of intrinsic material or chemical modification. Based on a profound understanding of the light-matter interaction in the nanoscale, optical design can propel the development of versatile LED color converters. Specifically, NANOPHOM explores the combination of rare-earth nanocrystals with different photonic materials, i.e. multilayers, surface textures and three-dimensional architectures to improve the performance of the color conversion process in light-emitting devices. The ultimate goal of this project is to develop large-area photonic materials with devised chromaticity and improved conversion and extraction efficiencies, which will enable a conscious use of the generated light. Indeed, these results are expected to find a direct application in the field of artificial lighting, especially in unconventional illumination applications such as roadway, stage or retail lighting, and applications beyond, like horticulture or healthcare, where highly specific and demanding specifications are required. Thus, our approach may have significant economic and environmental impact, reducing energy costs for lighting, lessening carbon dioxide emissions and minimizing light pollution.
NANOPHOM seeks to surpass the limits imposed by geometrical optics in the radiation shaping of light-emitting devices by means of nanophotonics. We aim at tailoring the emission properties of nano-sources using integrated nanostructured optical components, rather than following the traditional approach of intrinsic material or chemical modification. Based on a profound understanding of the light-matter interaction in the nanoscale, optical design can propel the development of versatile LED color converters. Specifically, NANOPHOM explores the combination of rare-earth nanocrystals with different photonic materials, i.e. multilayers, surface textures and three-dimensional architectures to improve the performance of the color conversion process in light-emitting devices. The ultimate goal of this project is to develop large-area photonic materials with devised chromaticity and improved conversion and extraction efficiencies, which will enable a conscious use of the generated light. Indeed, these results are expected to find a direct application in the field of artificial lighting, especially in unconventional illumination applications such as roadway, stage or retail lighting, and applications beyond, like horticulture or healthcare, where highly specific and demanding specifications are required. Thus, our approach may have significant economic and environmental impact, reducing energy costs for lighting, lessening carbon dioxide emissions and minimizing light pollution.
NANOPHOM succeeded to develop novel emitting materials based on the combination of nanophosphors with photonic architectures. It explored new ways of controlling their emission characteristics using dielectric or metallic nanostructures by design. In order to do so, a series of objectives, which represent relevant achievements per se, have been fulfilled. Luminescent properties of nanophosphors arise from the interplay among a variety of factors ranging from composition to crystallinity or surface properties. I have demonstrated that such properties can be tuned using integrated photonic systems, as opposed to conventional methods based on chemical engineering of the emitters. I have shown that it is possible to prepare transparent, bright and efficient thin nanophosphor films, being ultrafast annealing a key tool to maximize efficiency and transparency simultaneously. At the same time, I have made progress in developing tools to analyze the response of emitting devices, and the design and fabrication of photonic architectures to control the spontaneous emission of nanomaterials. On the one hand, we have prepared optically disordered materials as self-standing flexible coatings; we have investigated their properties as diffusers and shown enhanced nanophosphor emission. On the other hand, we have demonstrated that the interaction between resonant optical modes and the natural emission of nanophosphors integrated in an optical cavity allows precise control over the chromaticity and directionality of their emitted light without modifying the chemical composition of the emitters or degrade their efficiency, which represents a milestone in the field. In the same line of research, the periodic corrugation of nanophosphors films by nanoimprinting techniques allows a more efficient extraction of light in specific directions. In addition, we have proven that isolated metallic antennas in the vicinity of nanophosphors leads to radiative decay rate enhancement and that the integration of nanophosphors near the interface between a periodic multilayer and a metal thin film, which supports optical Tamm plasmons, permits to improve the emission of nanophosphors in devised directions. Finally, we have demonstrated a versatile and scalable method to prepare periodically corrugated nanophosphor surface patterns displaying strongly polarized and directional visible light emission. A combination of inkjet printing and soft lithography techniques has been employed to obtain arbitrarily shaped light emitting motifs. Our results support the thesis that the combination of nanophosphors and photonic architectures opens the door to develop improved light emitters, which confirm the success of the project. In fact, a precise control of the emission properties of the devices is linked to the growing interest of our society in the development of light sources with new functionalities.
NANOPHOM proposes the integration of nanostructured optical materials into light-emitting devices to attain full control over directionality and chromaticity of the color conversion process. Nanophosphors are central for many applications related to the generation of light because these nanomaterials feature exceptional thermal and chemical stability. However, such stability brings along an intrinsic complexity to alter their emission properties. The most common route to control the luminescence spectrum of nanophosphors is modifying their crystalline structure or their chemical composition at the expense of deteriorating the overall efficiency of the emitter. In spite of the intense research in this field, advances are always limited as a result of the difficulty to combine in a single slab both high optical quality, i.e. low scattering and thus high transparency, with efficient emission, which usually is achieved for large inorganic micron size phosphor crystals that strongly scatter light. In this context, NANOPHOM integrates a series of photonic approaches that control light−matter interaction at the sub-wavelength scale to tailor the emission of nanomaterials without altering their chemical composition, which represent an innovative approach. Our findings provide a significant advance in the understanding of nanostructured emitting materials for the development of versatile light sources.