Search

Core–shell perovskite nanocrystals (NCs) have emerged as a promising class of materials for optoelectronic applications due to their unique properties and stability. Although much research has been conducted on the shell growth mechanism and properties of the core–shell NCs, little is known about the role of shell thickness in determining their optical properties. Herein, a heteroepitaxial method is employed to prepare a series of core–shell FAPbBr3/CsPbBr3 NCs with different shell thicknesses. Through temperature‐dependent photoluminescence measurement, it is found that the electronic structure of core–shell FAPbBr3/CsPbBr3 NCs evolves from quasi‐type‐II to type‐I with the increase in shell thickness. This abnormal transition can be attributed to the thickened gradient alloy layer FA1‐xCsxPbBr3, which effectively relieves the lattice mismatch and releases strain in the NCs, resulting in variations in the bandgap between the core and the shell. Furthermore, the biexciton Auger lifetimes in these samples exhibit a non‐monotonic dependence on shell thickness, indicating the electronic structure transition. These results provide valuable insights into the relationship between shell thickness, electronic structure, and optical properties in core–shell perovskite NCs, which may offer guidance for the design of high‐performance optoelectronic devices. [ABSTRACT FROM AUTHOR]

Self‐assembly of nanocrystals into controlled structures while uncompromising their properties is one of the key steps in optoelectronic device fabrication. Herein, zigzag CsPbBr3 perovskite nanocrystals are demonstrated with a precise number of components with nanocube morphology, these can be successfully obtained through a dipole‐induced self‐assembly process. The addition of a trace amount of deionized water facilitates the transfer from CsPbBr3 nanocubes to intermediates of CsPb2Br5 and Cs3In2Br9, which then fastly release reaction monomers leading to further homogenous nucleation of CsPbBr3 nanocubes, followed by the formation of zigzag CsPbBr3 nanocrystals through a dipole‐induced self‐assembly process. Dipole moment along <110> axis is found to be the driving force for the assembly of nanocubes into zigzag nanocrystals. The zigzag CsPbBr3 nanocrystals exhibit desirable optical properties comparable to their nanocube counterparts and offer advantages for amplified spontaneous emission and lasing applications with low pump thresholds of 3.1 and 6.02 µJ cm−2, respectively. This study not only develops a strategy for producing highly controlled zigzag perovskite nanocrystals and provides insights on the dipole‐induced self‐assembly mechanisms, but also opens an avenue for their application in lasing. [ABSTRACT FROM AUTHOR]

Inorganic perovskite nanocrystals (NCs) have demonstrated a number of unique optical and electronic properties for optoelectronic applications. However, the physical properties of these nanostructures, such as the dynamics of charge carriers on different timescales and their effect on the optical recombination of carriers, are not yet fully understood. This work reports on a slow (>1 s) reversible quenching of the NC photoluminescence due to a light‐induced Stark effect involving defects on the surface of the NCs and the redistribution of photoexcited carriers onto the NC surface. This phenomenon can influence the operation of optoelectronic devices based on these NCs, including hybrid photosensors based on graphene decorated with inorganic perovskite NCs, revealing their prospects and limitations. [ABSTRACT FROM AUTHOR]

Core/shell structured metal halide perovskite nanocrystals (NCs) are emerging as a type of material with remarkable optical and electronic properties. Research into this field has been developing and expanding rapidly in recent years, with significant advances in the studies of the shell growth mechanism and in understanding of properties of these materials. Significant enhancement of both the stability and the optical performance of core/shell perovskite NCs are of particular importance for their applications in optoelectronic technologies. In this review, the recent advances in core/shell structured perovskite NCs are summarized. The band structures and configurations of core/shell perovskite NCs are elaborated, the shell classification and shell engineering approaches, such as perovskites and their derivative shells, semiconductor shell, oxide shell, polymer shell, etc. are reviewed, and the shell growth mechanisms are discussed. The prospective of these NCs in lighting and displays, solar cells, photodetectors, and other devices is discussed in the light of current knowledge, remaining challenges, and future opportunities. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals (NCs) have shown significant potential in light‐emitting applications due to the unique luminous properties, such as high color purity, tunability, and solution processability. However, the large‐scale production of perovskite NCs with high‐quality for meeting the commercial applications is still a challenge. Herein, a facile room‐temperature synthesis of ten‐gram‐scale FAPbX3 (FA+ = HC(NH2)2+, X = Br, or mixed halide system Cl/Br and Br/I) NCs by a high‐power ultrasonic‐assisted strategy and the electroluminescence for light‐emitting diodes (LEDs) is reported. The uniform high‐power radiation avoids the adverse effects caused by heating and stirring unevenness, and no inert gas is needed in the reaction process. Meanwhile, the room temperature reaction reduces the crystallization rate of the NCs, leading to the successful synthesis of ten‐gram‐scale high‐quality FAPbX3 perovskite NCs. The resulting NCs show size‐focus distribution and high photoluminescence quantum yields of 93%, and the adjustable photoluminescence spectra from 453 to 695 nm by manipulating halide compositions. Attributed to the acquired FAPbBr3 NCs, a high‐efficiency green LED with the maximum current efficiency of 61.3 cd A−1 and external quantum efficiency of 14.1% is also obtained. [ABSTRACT FROM AUTHOR]

Nanocrystal/polymer solid solar cells have the advantages of low-cost, simple process, and flexible manufacture. In this work, ternary solid solar cells based on FeS 2 and PbS nanocrystals exhibited photovoltaic conversion efficiency of 3.0% and 3.1%, respectively. As a kind of semiconductor with optical absorption in the visible and near-infrared regions, FeS 2 nanocrystals matched well with the solar radiation spectrum. Furthermore, PbS Nanocrystals could increase the number of electrons, due to its multiple exciton effect. Additionally, the FeS 2 nanocrystals solar cells showed high stability, with 83.3% of its initial efficiency remained after 15 weeks of exposure in air, and kept good stable performance at 20–80 °C. The photovoltaic conversion efficiency fluctuation magnitudes were also found to be smaller than quantum-dot sensitized solar cell under the same conditions. [ABSTRACT FROM AUTHOR]

The synthesis and utilization of an α-Mn2O3 nanocrystal catalyst for methanol-to-olefin reaction is described. A methanol conversion of 35% and a maximum selectivity of 80% toward ethylene were obtained at 250°C. In particular, formaldehyde, a primary intermediate for the reaction, was used to produce ethylene via a coupling reaction. A conversion of 45% and a selectivity of 66% to ethylene were achieved at 150°C in a formaldehyde stream. In situ diffuse reflectance infrared Fourier transform spectra reveal the formation of the surface CH2-containing species during reaction, which implies that the main pathway for formaldehyde coupling is probably through interactions of those intermediates. In addition, the weakly adsorbed oxygen on the α-Mn2O3 nanocrystal surface was found to play an important role in this reaction. © 2012 American Institute of Chemical Engineers AIChE J, 2012 [ABSTRACT FROM AUTHOR]