We developed a colloidal synthesis of CsPbBr perovskite nanocrystals (NCs) at a relative low temperature (90 °C) for the bright blue emission which differs from the original green emission (∼510 nm) of CsPbBr nanocubes as reported previously. Shapes of the obtained CsPbBr NCs can be systematically engineered into single and lamellar-structured 0D quantum dots, as well as face-to-face stacking 2D nanoplatelets and flat-lying 2D nanosheets via tuning the amounts of oleic acid (OA) and oleylamine (OM). They exhibit sharp excitonic PL emissions at 453, 472, 449, and 452 nm, respectively. The large blue shift relative to the emission of CsPbBr bulk crystal can be ascribed to the strong quantum confinement effects of these various nanoshapes. PL decay lifetimes are measured, ranging from several to tens of nanoseconds, which infers the higher ratio of exciton radiative recombination to the nonradiative trappers in the obtained CsPbBr NCs. These shape-controlled CsPbBr perovskite NCs with the bright blue emission will be widely used in optoelectronic applications, especially in blue LEDs which still lag behind compared to the better developed red and green LEDs.

Lead halide perovskite materials are thriving in optoelectronic applications due to their excellent properties, while their instability due to the fact that they are easily hydrolyzed is still a bottleneck for their potential application. In this work, water-resistant, monodispersed and stably luminescent cesium lead bromine perovskite nanocrystals coated with CsPbBr were obtained using a modified non-stoichiometric solution-phase method. CsPbBr 2D layers were coated on the surface of CsPbBr nanocrystals and formed a core-shell-like structure in the synthetic processes. The stability of the luminescence of the CsPbBr nanocrystals in water and ethanol atmosphere was greatly enhanced by the photoluminescence-inactive CsPbBr coating with a wide bandgap. The water-stable enhanced nanocrystals are suitable for long-term stable optoelectronic applications in the atmosphere.

CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (NCs) are promising materials due to their excellent optoelectronic properties. In this work, we show a successful partial and reversible cation exchange reaction between Pb and Mn in both CsPbCl3 NCs and CsMnCl3 NCs systems to yield luminescent CsPb1–x Mn x Cl3 NCs. By adjusting the reaction time, the photoluminescence from the exciton emission of CsPbCl3 and the electron transition of Mn2+ can be tuned gradually. This work highlights the feasibility of a postsynthetic interconversion of Pb2+ and Mn2+ in cesium lead chloride perovskite nanocrystals, which enables a new strategy to reduce the toxicity and adjust the emissions of CsPbCl3 NCs. In the end, we also discuss the plausible mechanisms for cation exchange in perovskite materials.

Lead halide perovskites and their applications in the optoelectronic field have garnered intensive interest over the years. Inorganic perovskites (IHP), though a novel class of material, are considered as one of the most promising optoelectronic materials. These materials are widely used in detectors, solar cells, and other devices, owing to their excellent charge‐transport properties, high defect tolerance, composition‐ and size‐dependent luminescence, narrow emission, and high photoluminescence quantum yield. In recent years, numerous encouraging achievements have been realized, especially in the research of CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) and surface engineering. Therefore, it is necessary to summarize the principles and effects of these surface engineering optimization methods. It is also important to scientifically guide the applications and promote the development of perovskites more efficiently. Herein, the principles of surface ligands are reviewed, and various surface treatment methods used in CsPbX3 NCs as well as quantum‐dot light‐emitting diodes are presented. Finally, a brief outlook on CsPbX3 NC surface engineering is offered, illustrating the present challenges and the direction in which future investigations are intended to obtain high‐quality CsPbX3 NCs that can be utilized in more applications.

CsPbCl 3 :Mn 2+ is a practical solution for obtaining red-orange light inorganic perovskite nanocrystals since CsPbI 3 is unstable. Increasing the concentration of Mn 2+ is an effective way to enhance the orange-red emission of CsPbCl 3 :Mn 2+ . However, the relationship between emission intensity of the Mn 2+ dopant and the concentration of Mn 2+ is very chaotic in different studies. As a transition metal ion, the electronic states of Mn 2+ are very sensitive to the crystal field environment. Here, the crystal field of the CsPbCl 3 :Mn 2+ nanocrystals was adjusted by co-doping other cations, and the concentration of Mn 2+ remained unchanged. Additionally, the crystal field strength of different samples was calculated. Compared with the CsPbCl 3 :Mn 2+ nanocrystals, the red-orange peak in the fluorescence spectrum of CsPbCl 3 :Mn 2+ , Er 3+ nanocrystals was redshifted from 580 to 600 nm and enhanced by 100 times successfully. The same experiment was carried out on CsPbCl 3 :Mn 2+ nanoplatelets at the same time to confirm the changed crystal field around Mn 2+ . The effect of co-doping cations on the luminescence properties of Mn 2+ is similar to that in nanocubes, and the mechanism was analyzed in detail.

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CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (NCs) are promising materials due to their excellent optoelectronic properties. This work shows a successful anion exchange reaction in CsPbBr3 nanowire (NW) systems with HCl gas resulting in a blue-green light-emitting CsPbBr3@CsPbBr3–x Cl x core–shell heterojunction. By adjusting the reaction time and the reaction temperature, the structure and light emission of the NWs can be adjusted. The core–shell heterojunction NCs are stably luminescent in 24 h. The rational mechanism of anion exchange in perovskite NCs is also investigated. The work highlights the feasibility of NWs heterogeneously prepared under the HC1 gas atmosphere, which provides a new strategy for studying the two- and multicolor luminescent perovskite NCs.

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