Hybrid organic–inorganic perovskite light‐emitting devices (LEDs) have recently shown the characteristic dynamical behavior of light‐emitting electrochemical cells (LECs), with intrinsic ionic migration creating an electric double layer and internal p‐i‐n structure and by accumulation of ions at interfaces. Therefore, the development of perovskite light‐emitting and photovoltaic devices based on the concepts of LEC operation attracts much attention and clarifies general physical processes in perovskites. Here, new directions that can further improve perovskite optoelectronic devices and extend their functionalities using additive mobile ions are overviewed: 1) enhancing single‐layer LECs with lithium additives for increased efficiency and longer lifetime; 2) facilitating ionic motion in three‐layer perovskite LECs to create dual‐functional devices, operating as both LEC and solar cells; and 3) creating truly ambipolar LEC devices with carbon nanotubes as stable electrodes that leverage ionic doping. Taken together, the use of these approaches provides a strategy to create efficient, stable, and bright LECs, which use advantages of both LED and LEC operation. It is discussed that how the LEC behavior in perovskite LEDs can be further improved to address the long‐term challenges in perovskite optoelectronics, such as stability, through approaches like ionically reconfigurable host/guest systems.

nanolasers generating laser emission in the range of 420-824 nm, [1][2][3][4] , which can be simply synthesized from solution. First of all, such perovskites possess relatively high refractive index (larger than 2), which allows for the creation of self-resonating gain media placed on various substrates: dielectrics, [1][2][3][4] metals, [5] nanostructured, [6] photonic crystals, [7] as well as integrated with waveguiding systems. [8][9][10] Also, chemically synthesized CsPbX 3 perovskite single crystals [11] of high quality and different shapes (cuboids, [12,13] wires, [1,14,15] plates [16][17][18] ) exhibit high levels of optical gain (typically ≈10 3 cm −1 ) [19] larger than those of thin polycrystalline films synthesized from solution (typically ≈10 2 cm −1 ). Thus, they provide a powerful technological tool for micro-and nanolasers fabrication, when their precise positioning is not required. However, the fabrication of large-scale films with crystalline quality as high as for single crystals would allow for overcoming many technological obstacles hindering lithographical creation [9,20,21] of highly controllable designs for lasing applications.In this paper, we develop a high-temperature recrystallization method for chemical synthesis of large-grain CsPbBr 3 thin Halide perovskite lasers based on CsPbBr 3 micro-and nanoscale crystals have demonstrated fascinating performance owing to their low-threshold lasing at room temperature and cost-effective fabrication. However, chemically synthesized thin films of CsPbBr 3 usually have rough polycrystalline morphology along with a large amount of crystal lattice defects and, thus, are mostly utilized for the engineering of light-emitting devices. This obstacle prevents their usage in many photonic applications. Here, a protocol to deposit large-grain and smooth CsPbBr 3 thin films is developed. Their high quality and large scale allow to demonstrate a maximum optical gain up to 12 900 cm −1 in the spectral range of 530-540 nm, which is a record-high value among all previously reported halide perovskites and bulk semiconductors (e.g., GaAs, GaN, etc.) at room temperature. Moreover, femtosecond laser ablation technique is employed to create high-quality microdisc lasers on glass from these films to obtain excellent lasing characteristics. The revealed critical roles of thickness and grain size for the CsPbBr 3 films with extremely high optical gain pave the way for development of low-threshold lasers or ultimately small nanolasers, as well as to apply them for polaritonic logical elements and integrated photonic chips.

Detection of hazardous volatile organic and inorganic species is a crucial task for addressing human safety in the chemical industry. Among these species, there are hydrogen halides (HX, X = Cl, Br, I) vastly exploited in numerous technological processes. Therefore, the development of a cost-effective, highly sensitive detector selective to any HX gas is of particular interest. Herein, we demonstrate the optical detection of hydrogen chloride gas with solution-processed halide perovskite nanowire lasers grown on a nanostructured alumina substrate. An anion exchange reaction between a CsPbBr3 nanowire and vaporized HCl molecules results in the formation of a structure consisting of a bromide core and thin mixed-halide CsPb(Cl,Br)3 shell. The shell has a lower refractive index than the core does. Therefore, the formation and further expansion of the shell reduce the field confinement for experimentally observed laser modes and provokes an increase in their frequency. This phenomenon is confirmed by the coherency of the data derived from XPS spectroscopy, EDX analysis, in situ XRD experiments, HRTEM images, and fluorescent microspectroscopy, as well as numerical modeling for Cl– ion diffusion and the shell-thickness-dependent spectral position of eigenmodes in a core–shell perovskite nanowire. The revealed optical response allows the detection of HCl molecules in the 5–500 ppm range. The observed spectral tunability of the perovskite nanowire lasers can be employed not only for sensing but also for their precise spectral tuning.

Hyperbolic metamaterials are a family of nanophotonic architectures allowing for the unique control of photonic local density of states. Such a property makes metamaterials prospective to use them with light-emitting objects or to apply as meta-electrodes for optoelectronic devices, where the control of recombination properties plays a decisive role. On the other hand, layered quasi-2D halide perovskites (Ruddlesden–Popper phase) attract high attention due to their low cost, broadband spectral tunability, and outstanding optoelectronic properties. Here, we show how to accelerate photoluminescence with smart engineering of photonic density of states (i.e., via the Purcell effect) by depositing a perovskite film on a hyperbolic metamaterial. We experimentally confirm acceleration of radiative recombination by almost 3 times. This effect can be useful in light-emitting devices, where interplay between radiative and non-radiative channels of charge carrier recombination is crucial.

Perovskite light-emitting diodes (pero-LEDs) is a rapidly developing technology that is supposed to supersede existing ones in the near future. In comparison with organic and A III B V analogues, pero-LEDs possess the following advantages: very narrow spectral linewidth of electroluminescence (EL), spectral tunability in the whole visible range and the possibility of a cost-effective large-scale fabrication by means of wet chemistry techniques. CsPbX3 (X = Cl, Br, I) are the most robust perovskites suitable for LEDs production due to their excellent optical properties. There are numerous reports describing green and red electroluminescence of such tribromide and triiodide materials, respectively, whereas a blue color is not easy to achieve. The main obstacles in the way of development of blue pero-LEDs based on chlorine salts are poor solubility of perovskite precursors in the same organic solvents as well as light- and an electric field-induced phase instability of mixed-halide (CsPbBr3−x Cl x ) materials. The latter leads to red-shift of EL spectrum with the increase in applied voltage. In this work, we present a design of a single-layer sky-blue pero-LED based on CsPbBr2 Cl-poly(ethylene oxide) (PEO) thin film, study the morphology of the emissive layer, its phase instability under UV illumination and in the electric field.