Growing large, oriented grains of perovskite often leads to efficient devices, but it is unclear if properties of the grains are responsible for the efficiency. Domains observed in SEM are commonly misidentified with crystallographic grains, but SEM images do not provide diffraction information. We study methylammoinium lead iodide (MAPbI3) films fabricated via flash infrared annealing (FIRA) and the conventional antisolvent (AS) method by measuring grain size and orientation using electron back-scattered diffraction (EBSD) and studying how these affect optoelectronic properties such as local photoluminescence (PL), charge carrier lifetimes, and mobilities. We observe a local enhancement and shift of the PL emission at different regions of the FIRA clusters, but we observe no effect of crystal orientation on the optoelectronic properties. Additionally, despite substantial differences in grain size between the two systems, we find similar optoelectronic properties. These findings show that optoelectronic quality is not necessarily related to the orientation and size of crystalline domains.

Localizing light to nanoscale volumes through nanoscale resonators that are low loss and precisely tailored in spectrum to properties of matter is crucial for classical and quantum light sources, cavity QED, molecular spectroscopy, and many other applications. To date, two opposite strategies have been identified: to use either plasmonics with deep subwavelength confinement yet high loss and very poor spectral control or instead microcavities with exquisite quality factors yet poor confinement. In this work we realize hybrid plasmonic–photonic resonators that enhance the emission of single quantum dots, profiting from both plasmonic confinement and microcavity quality factors. Our experiments directly demonstrate how cavity and antenna jointly realize large cooperative Purcell enhancements through interferences. These can be controlled to engineer arbitrary Fano lineshapes in the local density of optical states.

A general, one-step patterning technique for colloidal quantum dots by direct optical or e-beam lithography. Photons (5.5–91.9 eV) and electrons (3 eV–50 kV) crosslink and immobilize QDs down to tens of nm while preserving the luminescent properties.

the inhibitor from the matrix so unwanted reactions do not take place; and (ii) allow for the controlled release of the inhibitor (controlled kinetics or on-demand release). Many materials, shapes, sizes, and triggers have been developed using this basic principle ranging from microcapsules and nanocapsules relying on delamination to initiate the redox triggered release, to loaded nanosized porous zeolites and halloysite nanotubes where release relies on leaching and ion exchange. [1] Despite the clear success of the concept, two intrinsic limitations can be identified: (i) loading in nanoparticles is limited and bound to carrier-inhibitor pairs; and (ii) inhibitor release at a damage site greatly depends on particle size, release trigger, loading, and distribution. [2] As a consequence the long-term protection and protection at relatively big damages is compromised. [2b] Here we propose an alternative strategy based on the formation of low-density and/or humidity responsive interconnected paths of inhibitor inside the coating (i.e., inhibiting nanonetworks) as a way to overcome the above limitations. Such a strategy is based on recent findings by Hughes et al. [3] who recently attributed high inhibition of Cr(VI)-based coatings to the formation of inhibitor interconnected clusters and low density regions in the coating, thereby confirming previous modelling works. [2] In order to experimentally proof the validity of the concept we used the well-established process of electrospinning as the method to manufacture the responsive nanofiber mats containing corrosion inhibitors to form the inhibiting nano networks in the coatings. During the relatively simple process of electrospinning a membrane or fiber mat of polymeric fibers can be produced by applying an electric field between a spinneret, usually a needle of a syringe filled with polymer solution, and a grounded conductive collector. [4] By controlling the process parameters, spinning setup complexity, and the polymer solution physical properties, a large amount of geometries can be designed making it a suitable process for the design of membranes, drug delivery systems, and carriers of liquid self-healing agents for composites among others. [5] Cu-rich aluminum alloy AA2024-T3 is here used as the substrate to prove the corrosion inhibiting potential of the concept. This highly used aerospace grade aluminum alloy is known for its high corrosion In this work, a new concept is introduced for active corrosion protection at damaged sites aiming at overcoming existing limitations of currently proposed strategies based on dispersed inhibitor-loaded nanocontainers in coatings. The underlying principle is based on the formation of lowdensity and/or humidity responsive interconnected paths of inhibitor in the coating, what is called inhibiting nanonetworks. Such an approach allows for (on-demand) long-term local supply of corrosion inhibitor at the damage site.For the proof-of-concept, water responsive inhibiting nanonetworks based on polyvinyl alcohol and two known...

Accurately controlling light emission using nano-and microstructured lenses and antennas is an active field of research. Dielectrics are especially attractive lens materials due to their low optical losses over a broad bandwidth. In this work we measure highly directional light emission from patterned quantum dots (QDs) aligned underneath all-dielectric nanostructured microlenses. The lenses are designed with an evolutionary algorithm and have a theoretical directivity of 160. The fabricated structures demonstrate an experimental full directivity of 61 ± 3, three times higher than what has been estimated before, with a beaming half-angle of 2.6°. This high value compared to previous works is achieved via three mechanisms. First, direct electron beam patterning of QD emitters and alignment markers allowed for more localized emission and better emitter−lens alignment. Second, the lens fabrication was refined to minimize distortions between the designed shape and the final structure. Finally, a new measurement technique was developed that combines integrating sphere microscopy with Fourier microscopy. This enables complete directivity measurements, contrary to other reported values, which are typically only partial directivities or estimates of the full directivity that rely partly on simulations. The experimentally measured values of the complete directivity were higher than predicted by combining simulations with partial directivity measurements. High directivity was obtained from three different materials (cadmium-selenide-based QDs and two lead halide perovskite materials), emitting at 520, 620, and 700 nm, by scaling the lens size according to the emission wavelength.

Lead-halide perovskite (LHP) nanocrystals have proven themselves as an interesting material platform due to their easy synthesis and compositional versatility, allowing for a tunable band gap, strong absorption, and high photoluminescence quantum yield (PLQY). This tunability and performance make LHP nanocrystals interesting for optoelectronic applications. Patterning active materials like these is a useful way to expand their tunability and applicability as it may allow more intricate designs that can improve efficiencies or increase functionality. Based on a technique for II–VI quantum dots, here we pattern colloidal LHP nanocrystals using electron-beam lithography (EBL). We create patterns of LHP nanocrystals on the order of 100s of nanometers to several microns and use these patterns to form intricate designs. The patterning mechanism is induced by ligand cross-linking, which binds adjacent nanocrystals together. We find that the luminescent properties are somewhat diminished after exposure, but that the structures are nonetheless still emissive. We believe that this is an interesting step toward patterning LHP nanocrystals at the nanoscale for device fabrication.

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