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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. The interdependence of free carries, trap states and excitons in the light emission properties of CH3NH3PbBr3 perovskite thin films and their relationship to device performance is a subject of debate. Here, the authors investigate the role of non-radiative recombination and demonstrate that the photoluminescence is dominated by exciton radiative decay processes. [ABSTRACT FROM AUTHOR]

Thermal evaporation of green-light emitting perovskite (MaPbBr3) films is reported. Morphological studies show that a soft thermal treatment is needed to induce an outstanding crystal growth and film organization. Hetero-structured light-emitting diodes, embedding as-deposited and annealed MAPbBr3 films as active layers, are fabricated and their performances are compared, highlighting that the perovskite evolution is strongly dependent on the growing substrate, too. [ABSTRACT FROM AUTHOR]

Highlights: [•] White OLEDs with both high luminous efficiency and color rendering index (CRI). [•] Multi-resonant emission by coupling three microcavities. [•] High efficiency ITO-free white OLED on flexible substrates. [ABSTRACT FROM AUTHOR]

Hybrid electrochromic (EC) devices present an interesting configuration in which the advantage of both solid-state and liquid-based devices can be combined in order to optimize the device performances. In this configuration, a solid-state EC material is combined with a redox couple dissolved in the electrolyte. The redox electrolyte offers an unlimited charge capacity, thus allowing to fully exploit the electrochromic properties of the EC material. Here, we present a thiolate/disulphide (T−/T 2) redox couple as a new redox shuttle for EC devices. In order to transfer the advantages of the redox couple to a solid state device, it was combined with a fully transparent thermally curable vinyl-acetate polymer. The obtained EC device was compared with that based on I−/I 3 − showing higher transparency in the visible region of the solar spectrum and higher coloration efficiency. Most interestingly, the device based on T−/T 2 shows a slower self-bleaching process and it only loses 30% of its coloration after 1 h at open circuit. Such characteristic represents a great advantage for smart windows applications since it is not necessary to apply potential to maintain the device coloration, thus allowing a great energy saving. [Display omitted] • Development of transparent electrolyte based on disulfide/thiolate (T 2 /T−) redox couple. • Exploitation of transparent electrolyte in hybrid electrochromic device. • Electrochemical and optical characterization of redox couple and complete electrochromic device. [ABSTRACT FROM AUTHOR]

This experimental work reports the activities of design, fabrication and characterization of an innovative solid-state electrochromic device, deposited on a single substrate with high transparency in the bleached conditions and a wide modulation of transmittance (ΔT of 60% at 750 nm) both in the visible and near-infrared wavelengths. A tailored formulation of the solid electrolytes, based on sulfonated tetrafluoroethylene-based fluoropolymer-copolymer dispersions and the accurate design of a suitable layer of porous tin oxide nanoparticles provided high coloration and bleaching kinetics and recovery of the pristine conditions, even after 500 complete cycles. Devices were scaled-up to 10 × 10 cm2 size, without mechanical and aesthetic defects and relevant homogeneity, throughout the coloration and bleaching processes. Furthermore, this device shows the further feature to be a low-emissivity dynamic solar control film, highly compatible with integration within insulated glazed units. • A simplified architecture for solid-state electrochromic devices. • High transparency (>80%) and transmittance modulation (>60%), fast kinetics. • Fair low-emissive properties (ε = 0.52) of scaled-up prototypes, after 500 cycles. [ABSTRACT FROM AUTHOR]