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In this work, we present a binary assembly model that can predict the co-assembly structure and spatial frequency spectra of monodispersed nanoparticles with two different particle sizes. The approach relies on an iterative algorithm based on geometric constraints, which can simulate the assembly patterns of particles with two distinct diameters, size distributions, and at various mixture ratios on a planar surface. The two-dimensional spatial-frequency spectra of the modeled assembles can be analyzed using fast Fourier transform analysis to examine their frequency content. The simulated co-assembly structures and spectra are compared with assembled nanoparticles fabricated using transfer coating method are in qualitative agreement with the experimental results. The co-assembly model can also be used to predict the peak spatial frequency and the full-width at half-maximum bandwidth, which can lead to the design of the structure spectra by selection of different monodispersed particles. This work can find applications in fabrication of non-periodic nanostructures for functional surfaces, light extraction structures, and broadband nanophotonics.

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.

Organometal halide perovskite light emitting diodes (LEDs) have attracted a lot of attention in recent years, owing to the rapid progress in device efficiency. However, their short operational lifetime severely impedes the practical uses of these devices. The operating stability of perovskite LEDs are due to degradation due to ambient environment and degradation during operation. The former can be suppressed by encapsulation while the latter one is the intrinsic degradation due to the electrochemical stability of the perovskite materials. In addition, perovskites also suffer from ion migration which is a major degradation mechanism in perovskite LEDs. In this review, we specifically focus on the operational stability of perovskite LEDs. The review is divided into two parts: the first part contains a summary of various degradation mechanisms and some insight on the degradation behavior and the second part is the strategies how to improve the operational stability, especially the strategies to suppress ion migration. Based on the current advances in the literature, we finally present our perspectives to improve the device stability.

Metal halide perovskites have drawn tremendous attention in optoelectronic applications owing to the rapid development in photovoltaic and light‐emitting diode devices. More recently, these materials are demonstrated as excellent gain media for laser applications due to their large absorption coefficient, low defect density, high charge carrier mobility, long carrier diffusion length, high photoluminescence quantum yield, and low Auger recombination rate. Despite the great progress in laser applications, the development of perovskite lasers is still in its infancy and the realization of electrically pumped lasers has not yet been demonstrated. To accelerate the development of perovskite‐based lasers, it is important to understand the fundamental photophysical characteristics of perovskite gain materials. Here, the structure and gain behavior in various perovskite materials are discussed. Then, the effects of charge carrier dynamics and electron–phonon interaction on population inversion in different types of perovskite materials are analyzed. Further, recent advances in perovskite‐based lasers are also highlighted. Finally, a perspective on perovskite material design is presented and the remaining challenges of perovskite lasers are discussed.