Photonic crystals have proven their potential and are nowadays a familiar concept. They have been approached from many scientific and technological flanks. Among the many techniques devised to implement this technology self-assembly has always been one of great popularity surely due to its ease of access and the richness of results offered. Self-assembly is also probably the approach entailing more materials aspects owing to the fact that they lend themselves to be fabricated by a great many, very different methods on a vast variety of materials and to multiple purposes. To these well-known material systems a new sibling has been born (photonic glass) expanding the paradigm of optical materials inspired by solid state physics crystal concept. It is expected that they may become an important player in the near future not only because they complement the properties of photonic crystals but because they entice the researchers' curiosity. In this review a panorama is presented of the state of the art in this field with the view to serve a broad community concerned with materials aspects of photonic structures and more so those interested in self-assembly.

The photophysical properties of films of organic–inorganic lead halide perovskites under different ambient conditions are herein reported. We demonstrate that their luminescent properties are determined by the interplay between photoinduced activation and darkening processes, which strongly depend on the atmosphere surrounding the samples. We have isolated oxygen and moisture as the key elements in each process, activation and darkening, both of which involve the interaction with photogenerated carriers. These findings show that environmental factors play a key role in the performance of lead halide perovskites as efficient luminescent materials.

Herein we present a combined study of the evolution of both the photoluminescence (PL) and the surface chemical structure of organic metal halide perovskites as the environmental oxygen pressure rises from ultrahigh vacuum up to a few thousandths of an atmosphere. Analyzing the changes occurring at the semiconductor surface upon photoexcitation under a controlled oxygen atmosphere in an X-ray photoelectron spectroscopy (XPS) chamber, we can rationalize the rich variety of photophysical phenomena observed and provide a plausible explanation for light-induced ion migration, one of the most conspicuous and debated concomitant effects detected during photoexcitation. We find direct evidence of the formation of a superficial layer of negatively charged oxygen species capable of repelling the halide anions away from the surface and toward the bulk. The reported PL transient dynamics, the partial recovery of the initial state when photoexcitation stops, and the eventual degradation after intense exposure times can thus be rationalized.

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A method for the fabrication of engineered planar defects inside opals (see Figure) is presented. These defects act as photonic microcavities, introducing a localized state in the gap. The scalability of the defect allows for the tuning of the spectral position of the defect by changing the size of the defect relative to the periodicity of the lattice.

A hybrid photonic–plasmonic crystal structure comprising a close‐packed monolayer of dielectric spheres deposited on plasmon‐supporting gold substrate is investigated. The spontaneous emission of organic dyes embedded in the beads experiences a strong modification in intensity, polarization, and directionality. These facts are accounted for considering the hybridization of modes arising from the photonic and plasmonic components of the structure.

CommuniCation(1 of 7) 1601087 synthesis of PbI 2 nanocrystals and their subsequent reaction with CH 3 NH 3 I 3 to produce the corresponding organic-inorganic lead halide quantum dots. [4] More recently, powders of porous silica exhibiting a 2D hexagonal mesopore structure have been used as templates to synthesize MAPbI 3 nanocrystals. [14,15] This approach proved to be suitable to attain bright and stable emission whose spectrum could be controlled by the average pore size of the matrix. However, most applications foreseen for hybrid perovskites require the use of thin films of high optical quality, as well as versatility regarding the composition of the scaffold employed. In order to achieve this goal, mesostructures with geometries other than the hexagonal one previously employed to host perovskite nanocrystals must be used, since the characteristic tubular channels tend to lie parallel to the substrate when the porous material is shaped as a film, becoming inaccessible from the top surface. This prevents their infiltration with perovskite precursors. Very recently, MAPbI 2 X (X = Cl, Br, I) compounds have been synthesized inside metal organic framework films, [16] but no control over the size and optical properties of MAPbI 3 was demonstrated.In this Communication, we demonstrate a synthetic route to obtain stabilized MAPbI 3 nanocrystals embedded in thin metal oxide films that display well-defined and adjustable quantum confinement effects over a wide range of 0.34 eV. Mesostructured TiO 2 and SiO 2 films displaying an ordered 3D pore network are prepared by evaporation induced self-assembly of a series of organic supramolecular templates in the presence of metal oxide precursors. The pores in the inorganic films obtained after thermal annealing are then used as nanoreactors to synthesize MAPbI 3 crystallites with narrow size distribution and average radius comprised between 1 and 4 nm, depending on the template of choice. Both the static and dynamic photoemission properties of the ensemble display features distinctive of the regime of strong quantum confinement. Photoemission maps demonstrate that the spectral and intensity properties of the luminescence extracted from the perovskite quantum dot loaded films are homogeneous over squared centimeters areas. In addition, the photoemission stationary state is reached 10 4 times faster than in a MAPbI 3 solid film. One of the most versatile strategies to tune the optical properties of a semiconductor consists in reducing its size until it becomes of the order of the exciton Bohr radius and quantum confinement effects arise. [1] Different methods have been developed to try to controllably diminish the size of methyl ammonium lead halide (MAPbX 3 , X = Cl, Pb, I) crystals, [2][3][4][5][6][7] motivated by the interest these perovskites generate in the field of optoelectronics. [8][9][10][11][12] Efforts in obtaining dispersions of hybrid organic-inorganic perovskite nanocrystals for optoelectronic applications have mainly focused on MAPbBr 3 and MAPbBr x I 3-x , a...

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