Robust Ultralong Lead Halide Perovskite Microwire Lasers

Metal-Halide Perovskite Lasers: Cavity Formation and Emission Characteristics

Hybrid metal-halide perovskites (MHPs) have shown remarkable optoelectronic properties as well as facile and cost-effective processability. With the success of MHP solar cells and light-emitting diodes, MHPs have also exhibited great potential as gain media for on-chip lasers. However, to date, stable operation of optically pumped MHP lasers and electrically driven MHP lasers-an essential requirement for MHP laser's insertion into chip-scale photonic integrated circuits-is not yet demonstrated. The main obstacles include the instability of MHPs in the atmosphere, rudimentary MHP laser cavity patterning methods, and insufficient understanding of emission mechanisms in MHP materials and cavities. This review aims to provide a detailed overview of different strategies to improve the intrinsic properties of MHPs in the atmosphere and to establish an optimal MHP cavity patterning method. In addition, this review discusses different emission mechanisms in MHP materials and cavities and how to distinguish them.

Enhanced Photoluminescence and Random Lasing Emission in TiO2-Decorated FAPbBr3 Thin Films

Herein, titanium-dioxide-decorated organic formamidinium lead bromide perovskite thin films grown by the one-step spin-coating method are studied. TiO₂ nanoparticles are widespread in FAPbBr₃ thin films, which changes the optical properties of the perovskite thin films effectively. Obvious reductions in the absorption and enhancements in the intensity of the photoluminescence spectra are observed. Over 6 nm, a blueshift of the photoluminescence emission peaks is observed due to 5.0 mg/mL TiO₂ nanoparticle decoration in the thin films, which originates from the variation in the grain sizes of the perovskite thin films. Light intensity redistributions in perovskite thin films are measured by using a home-built confocal microscope, and the multiple scattering and weak localization of light are analyzed based on the scattering center of TiO₂ nanoparticle clusters. Furthermore, random lasing emission with sharp emission peaks is achieved in the scattering perovskite thin films with a full width at the half maximum of 2.1 nm. The multiple scattering of light, the random reflection and reabsorption of light, and the coherent interaction of light within the TiO₂ nanoparticle clusters play important roles in random lasing. This work could be used to improve the efficiency of photoluminescence and random lasing emissions, and it is promising in high-performance optoelectrical devices.

Photosensitive Dielectric 2D Perovskite Based Photodetector for Dual Wavelength Demultiplexing

Stacked 2D perovskites provide more possibilities for next generation photodetector with more new features. Compared with its excellent optoelectronic properties, the good dielectric performance of metal halide perovskite rarely comes into notice. Here, a bifunctional perovskite based photovoltaic detector capable of two wavelength demultiplexing is demonstrated. In the Black Phosphorus/Perovskite/MoS₂ structured photodetector, the comprehensive utilization of the photosensitive and dielectric properties of 2D perovskite allows the device to work in different modes. The device shows normal continuous photoresponse under 405 nm, while it shows a transient spike response to visible light with longer wavelengths. The linear dynamic range, rise/decay time, and self-powered responsivity under 405 nm can reach 100, 38 µs/50 µs, and 17.7 mA W^-1 , respectively. It is demonstrated that the transient spike photocurrent with long wavelength exposure is related to the illumination intensity and can coexist with normal photoresponse. Two waveband-dependent signals can be identified and used to reflect more information simultaneously. This work provides a new strategy for multispectral detection and demultiplexing, which can be used to improve data transfer rates and encrypted communications. This work mode can inspire more multispectral photodetectors with different stacked 2D materials, especially to the optoelectronic application of the wide bandgap, high dielectric photosensitive materials.

Ultraviolet photodetector based on RbCu2I3microwire

Copper-based halide perovskites have shown great potential in lighting and photodetection due to their excellent photoelectric properties, good stability and lead-free nature. However, as an important piece of copper-based perovskites, the synthesis and application of RbCu₂I₃have never been reported. Here, we demonstrate the synthesis of high-quality RbCu₂I₃microwires (MWs) by a fast-cooling hot saturated solution method. The prepared MWs exhibit an orthorhombic structure with a smooth surface. Optical measurements show the RbCu₂I₃MWs have a sharp ultraviolet absorption edge with 3.63 eV optical band gap and ultra-large stokes shift (300 nm) in photoluminescence. The subsequent photodetector based on a single RbCu₂I₃MW shows excellent ultraviolet detection performance. Under the 340 nm illumination, the device shows a specific detectivity of 5.0 × 10⁹Jones and a responsivity of 380 mA·W^-1. The synthesis method and physical properties of RbCu₂I₃could be a guide to the future optoelectronic application of the new material.

A Hybrid Functional Study on Perovskite-Based Compounds CsPb1-αZnαI3-βXβ (X = Cl or Br)

Inorganic perovskites have attracted a great deal of attention because of their stability. Unfortunately, a weak optical response and the toxicity of lead are hampering their development. Motivated by these facts, we focus herein on the perovskite-based doped series CsPb_1-αZn_αI_3-βX_β (X = Cl or Br). The geometric structures and the electronic and optical properties of CsPb_1-αZn_αI_3-βX_β (X = Cl or Br) are investigated systematically by hybrid functional theory. Analysis of the electronic properties indicates that Zn/Cl/Br mono-doping and co-doping efficiently tune bandgaps. Moreover, we find that the ability to obtain electrons for CsPb_0.625Zn_0.375I₂Cl is superior to the abilities of the others, which implies a stronger electron transition. In addition, CsPb_0.625Zn_0.375I₂Cl and CsPb_0.625Zn_0.375I₂Br show stronger visible-light responses in the range of 467-780 nm. Both CsPb_0.625Zn_0.375I₂Cl and CsPb_0.625Zn_0.375I₂Br are hence good choices for photovoltaic applications. Furthermore, the physically accessible region is also explored herein. These findings shed new light on the design of highly efficient and low-lead perovskite-based optoelectronic materials.

Dehydration-activated structural phase transition in a two-dimensional hybrid double perovskite

As a feasible lead-free scheme, organic-inorganic hybrid double perovskites show many excellent properties, including ferroelectricity, ferroelasticity, self-powered circularly polarized light detection and so on. In this work, the solid-to-solid structural phase transition of a two-dimensional hybrid double perovskite (CHA)₄CuBiI₈ was successfully activated via the dehydration of (CHA)₄CuBiI₈·H₂O, which was proven by differential scanning calorimetry (DSC) and temperature-dependent dielectric measurements. Using variable-temperature single-crystal X-ray diffractometry, the cause behind the phase transition of (CHA)₄CuBiI₈ was determined to be the overall coordination of distortion and movement of the inorganic skeleton and thermal deformation of the cationic structure. In addition, the substance after dehydration shows good stability in multiple reversible switching during dielectric tests. The interesting dehydration-activated results of the material contribute towards a further expansion of the properties and potential application of hybrid double perovskites.