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All‐inorganic metal halide perovskites, such as CsPbX3 (X = Br, Cl, or I), have attracted significant interest for a new generation of integrated, high‐performance optoelectronic devices. To realize the full potential of layer‐by‐layer devices, perovskite crystal thin films are preferred over crystal ingots, considering carrier loss during carrier transport. The space‐confined method is a facile way of fabricating perovskite crystal films in a geometrically confined space to break the isotropic growth. Many researchers have reported effective preparation of large‐area perovskite films using this method. However, most space‐confined methods require growth in a liquid phase (solution), which can cause uncontrollable nucleation, surface traps, and unsatisfactory device performance. In this work, a pure solid‐state space‐confined strategy to grow CsPbBr3 films for the first time without relying on solution conditions is developed. The regular shapes of CsPbBr3 films prepared by this solid‐state space‐confined strategy can function as effective multimode and single‐mode Fabry–Perot (F–P) microlasers under optical pumping. This work overcomes the challenge that the conventional space‐confined method can only be adapted to the liquid phase. It also opens a new approach for making high‐quality microlasers, which are significant for photonic integrated circuits and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Mixed-cation lead mixed-halide perovskites simultaneously possess structural stability and high power conversion efficiency. A thorough study of both carrier and exciton dynamics is needed to understand the photophysical properties that underpin its superior photovoltaic performance. By utilizing a broadband transient absorption spectroscopy, we observe the carrier and exciton dynamics in a FA0.85Cs0.15Pb(I0.97Br0.03)3 (FCPIB) perovskite by simultaneously resolving the carrier and exciton contribution to the transient change of the absorption spectra, from which the carrier density and exciton oscillator strength can be determined. Our data reveal a quick and significant conversion of the photogenerated carriers to excitons, on top of the usual carrier recombination process. Moreover, the decay of carrier density shows a change of kinetics from a second-order recombination at high pump fluence to a third-order recombination at low pump fluence. Our analysis utilizes band anharmonicity, presents an independent determination of electronic temperature and quasi-Fermi energy, and reveals an interesting interplay among the processes of carrier cooling, exciton formation/decay and carrier recombination, all as a function of time after photoexcitation. Our work demonstrates the use of pump fluence as a knob to tune the relative populations of carriers and excitons in halide perovskite materials. Lead halide perovskites have many suitable features as materials for solar cells and a better understanding of the underlying physics will help engineer improved performance values. Here, the authors use broadband transient absorption spectroscopy to probe the excited state dynamics of mixed-halide perovskites and the role of excitons and carriers. [ABSTRACT FROM AUTHOR]

In the past decade, halide perovskite materials have captivated a great deal of attention for the application in optoelectronic devices. To realize the commercialization of optoelectronic devices made from this exhilarating material system, in particular to boost the efficiency and the stability, the formation mechanisms of defects, their impact on device performance and lifetime and the way to overcome them must be thoroughly investigated. In this review, the current understanding of the defect creation mechanism in as-synthesized and environment-exposed samples will be presented. The defect induced phenomenon and their impact on the material properties and device performances will be explained. The various defect characterization techniques will be summarized regarding their working principles and limitations. The defect engineering including both physical and chemical methods will be discussed in detail. We believe that although there are still unsolved puzzles in the field, the research on the defect mechanism and engineering is of great significance in making halide perovskites into real applications. [ABSTRACT FROM AUTHOR]

Recently, newly engineered all-inorganic cesium lead halide perovskite nanocrystals (IPNCs) (CsPbX3, X = Cl, Br, I) are discovered to possess superior optical gain properties appealing for solution-processed cost-effective lasers. Yet, the potential of such materials has not been exploited for practical laser devices, rendering the prospect as laser media elusive. Herein, the challenging but practically desirable vertical cavity surface emitting lasers (VCSELs) based on the CsPbX3 IPNCs, featuring low threshold (9 µJ cm−2), directional output (beam divergence of ≈3.6°), and favorable stability, are realized for the first time. Notably, the lasing wavelength can be tuned across the red, green, and blue region maintaining comparable thresholds, which is promising in developing single-source-pumped full-color visible lasers. It is fully demonstrated that the characteristics of the VCSELs can be versatilely engineered by independent adjustment of the cavity and solution-processable nanocrystals. The results unambiguously reveal the feasibility of the emerging CsPbX3 IPNCs as practical laser media and represent a significant leap toward CsPbX3 IPNC-based laser devices. [ABSTRACT FROM AUTHOR]

All-inorganic cesium lead halide perovskites have been emerging as the promising semiconductor materials for next-generation optoelectronics. However, the fundamental question of how the environmental atmosphere affects their photophysical properties, which is closely related to the practical applications, remains elusive. Here, we report the dynamic switching between radiative exciton recombination and non-radiative carrier trapping in CsPbBr3 by controlling the atmospheric conditions. Specifically, we show that the photoluminescence (PL) intensity from the CsPbBr3 crystals can be boosted by ~ 60 times by changing the surrounding from vacuum to air. Based on the comprehensive optical characterization, near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) as well as density functional theory (DFT) calculations, we unravel that the physisorption of oxygen molecules, which repairs the trap states by passivating the PL-quenching bromine vacancies, is accountable for the enhanced PL in air. These results are helpful for better understanding the optical properties of all-inorganic perovskites. Perovskite-based optoelectronics are expected to become an important component of devices such as solar cells and light-emitting diodes. However, how they are affected by environmental conditions is still not fully understood. The authors investigate the mechanisms, which occur for inorganic perovskites when in contact with ambient atmosphere and how this could potentially impact upon device performance. [ABSTRACT FROM AUTHOR]

CsPbX3 (X: Cl, Br, I) quantum dots are prepared by injecting small amounts of a precursor solution consisting of Cs2CO3, oleic acid (OA), and octadecene (ODE) (150 °C, 1.5 h) to a solution comprising ODE, OA, oleylamine, and PbX2 at 160 °C. [ABSTRACT FROM AUTHOR]