Metal-halide semiconductor perovskites have received great attention for the development of stable and efficient light emitting diodes and lasers, since they combine high charge carrier mobility and light emission spectral-purity with low-cost fabrication methods. Nevertheless, the role of excitons, free carries and trap states in perovskite light emission properties is still unclear due to their interdependence. In this paper we selectively manage trapping and light emission mechanisms by a reversible laser-assisted trap-passivation process performed on a CH₃NH₃PbBr₃ perovskite layer, coupled to the inner modes of a high-quality micro-cavity, which only affects the radiative recombination. We show that photoluminescence is dominated by exciton radiative decay process and that trap states passivation increases the exciton gemination rate by reducing coulombic scattering of free electrons due to the ionized impurities. This picture provides a more general description than the model based on trap states-free Saha thermodynamic equilibrium between photo-generated species.

With the main objective being to develop photochromic smart textiles, in this paper, we studied the photochromic behavior of WO_3-x nanocrystals (NCs) cooperatively interacting with variable amounts of TiO₂ NCs. We tested several blends of WO_3-x:TiO₂ NCs, admixed in different compositions (relative molar ratio of 4:0, 3:1, 2:2, 1:3, 0:4) and electrostatically interfacing because of opposite values of Z-potential, for photo-induced chromogenic textiles. We further monitored the photochromic sensitivity of NC-impregnated textiles after exposure to a few solvents (i.e., methanol, ethanol, and isopropanol) or when over-coated with different polymeric matrices such as natural cellulose or ionic conductive Nafion. The optimization of the compositions of the WO_3-x:TiO₂ blends embedded in polymeric matrices, allowed the nanostructured photochromic textiles to show rapid and tunable coloration (<5 min) and bleaching kinetics (~5 in at 75 °C or 6 h at room temperature) along with good recovery and cycling stability. This study features a simple strategy for the widespread application of WO_3-x:TiO₂-based photochromic smart textiles.

Bio-based polymers are attracting great interest due to their potential for several applications in place of conventional polymers. In the field of electrochemical devices, the electrolyte is a fundamental element that determines their performance, and polymers represent good candidates for developing solid-state and gel-based electrolytes toward the development of full-solid-state devices. In this context, the fabrication and characterization of uncrosslinked and physically cross-linked collagen membranes are reported to test their potential as a polymeric matrix for the development of a gel electrolyte. The evaluation of the membrane’s stability in water and aqueous electrolyte and the mechanical characterization demonstrated that cross-linked samples showed a good compromise in terms of water absorption capability and resistance. The optical characteristics and the ionic conductivity of the cross-linked membrane, after overnight dipping in sulfuric acid solution, demonstrated the potential of the reported membrane as an electrolyte for electrochromic devices. As proof of concept, an electrochromic device was fabricated by sandwiching the membrane (after sulfuric acid dipping) between a glass/ITO/PEDOT:PSS substrate and a glass/ITO/SnO₂ substrate. The results in terms of optical modulation and kinetic performance of such a device demonstrated that the reported cross-linked collagen membrane could represent a valid candidate as a water-based gel and bio-based electrolyte for full-solid-state electrochromic devices.

A set of engineered photoluminescent foils have been realized by incorporating three different types of CdS/CdSe colloidal nanorods into a transparent poly(methyl methacrylate) matrix.

The understanding and management of the optical behavior of dielectric/metal/dielectric (DMD)-based electrodes are crucial for the design of fully transparent OLEDs. Specifically, the chromatic stability with the viewing angle of white OLED emission remains an important issue due to the angle dependence of internal reflection at the organic/electrode interface as the wavelength varies. The purpose of the present work is to provide a complete analysis of the optical behavior of DMD structures by Variable Angle Spectroscopic Ellipsometry in order to optimize the transmittance of DMD-based transparent white OLEDs over a wide viewing angle. The analysis of the optical modes contributing to power dissipation reveals that the reduction of plasmonic and waveguided modes is related to the antireflection properties of the DMD electrode. This results in a simultaneous significant improvement in the absolute value of the transmittance across the full visible spectral range and in the color stability of white OLED emission over a wide viewing cone of 120°, thus paving the way for a new generation of transparent white lighting sources.