Colloidal semiconductor nanocrystals (NCs) attract significant interest in recent years due to their narrow and tunable emission wavelength in the visible range, as well as high photoluminescence quantum yield (PLQY), which are highly desired in display technologies. The high-quality NCs have been recognized as vital luminescent materials in realizing next-generation display devices. With further development, NCs with near-unity PLQY have been successfully synthesized through engineering of the core/shell heterostructure. However, as the external quantum efficiency (EQE) of the nanocrystal light-emitting diodes (LEDs) approaches the theoretical limit of about 20%, the low out-coupling factor proposes a challenge of enhancing the performance of a device when using the spherical QDs. Hence, the anisotropic NCs like nanoplatelets (NPLs) are proposed as promising solutions to improve the performance of nanocrystal LEDs. In this review, we will summarize the synthetic strategies of two-dimensional (2D) NPLs at first. Then, we will introduce fundamental concepts of LEDs, the main approaches to realize LEDs based on nanoplatelets, and the recent progress. Finally, the challenges and opportunities of LEDs based on anisotropic NCs are also presented.

A trade‐off between open‐circuit voltage (V OC) and high short‐circuit (J SC) becomes one of the most vital problems limiting further improvement in polymer solar cells' (PSCs) efficiency. In this work, two asymmetric polymer donors PBDT‐F‐2TC and PBDT‐SF‐2TC are designed and synthesized. When blended with a state‐of‐the‐art acceptor IT‐4F with low lowest‐unoccupied molecular orbital level, simultaneously high V OC (up to 0.94 V) and J SC (up to 20.73 mA cm−2) are obtained for both copolymers. Note that the V OC value of 0.94 V is the highest value of PSCs based on IT‐4F reported so far. The simultaneously improved V OC and J SC in resulting devices are discovered from the deep highest‐occupied molecular orbital levels (−5.5 to −5.7 eV) and the hyperchromic effect of the polymers, the small driving force, and the small energy loss during the charge transfer, due to the synergistic effect of asymmetric carboxylate unit and fluorine/sulfur atoms. More importantly, thanks to the asymmetric 2TC, both PBDT‐F‐2TC‐ and PBDT‐SF‐2TC‐based PSCs can be successfully processed by non‐halogenated solvent 1,2,4‐trimethylbenzene (TMB) to yield device efficiencies of 10.29% and 10.39%, respectively, which are the maximum values for non‐fullerene PSCs fabricated using the eco‐friendly solvent TMB.

Formamidinium lead bromide (FAPbBr3) nanocrystals (NCs) have been demonstrated to exhibit ideal ultrapure green luminescence at 530 nm and to hold great potential in light-emitting diodes, by potentially overcoming the difficulties facing cesium lead bromide (CsPbBr3) NCs. However, compared to all-inorganic lead halide perovskite NCs, organic–inorganic hybrid FAPbBr3 NCs are sensitive to moisture, oxygen, and heat due to their intrinsic instability caused by the organic cations (FA+). Herein, we present an epitaxial growth method for the overgrowth of a large-band-gap cesium lead halide (Cs4PbBr6) shell on the surface of FAPbBr3 NCs. The resulting core/shell NCs show a near-unity photoluminescence quantum yield (PLQY) of 97.1%, the emission with full width at half-maxima of 88 meV, and long-term environmental stability. The introduction of Cs+ into FAPbBr3 NCs can inhibit the migration of FA+ and suppress the phase transformation from cubic phase to tetragonal phase at 60 °C. Furthermore, the existence of shell can provide stronger exciton confinement and improve the thermal stability of FAPbBr3 NCs. The core/shell perovskite NCs developed in this study have the advantages of high PLQY and good stability and may contribute to the field of light-emitting diodes (LEDs).

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Blue-Green Infrastructure (BGI) ponds have an important function of alleviating flood risk and provide water quality improvements among other multiple benefits. Characterisation of bottom sediments and suspended particulate matter (SPM) is understudied, but is indispensable for assessing the ponds' functioning because of their role in biogeochemical cycling and pollutant adsorption. Here we report on the analysis of particle sizes and chemistry from multiple locations. The results have shown that SPM in these ponds includes particles of both biological and abiotic origin, and the in situ produced organic matter constitutes a major part of SPM. The relevance of biological processes is often overlooked, but a combination of SEM observations and chemical analysis highlights its primary importance for characterisation of the particulate matter. A considerable proportion of both suspended and sedimented particulates is smaller than 100 microns. There is normally a large fraction of small silt-sized particles, and often a considerable proportion of very fine particles (clay-size). Although for some spectra unimodal distribution has been observed, in many cases the revealed particle size distribution (PSD) was bimodal, and in some instances more than two modes were revealed. A complex PSD would be expected to result from a combination of simple unimodal distributions. Hence the multimodality observed may have reflected contributions from different sources, both abiotic and biological. Furthermore, many smaller particles appear to be interconnected by detrital matter. Among chemical elements routinely detected within the SPM in significant concentrations were Si, Al, Ca, Mg, Fe, K, Mn, P, Cl and S. In a number of cases, however, there were less expected elements such as Ti, Y, Mo, Cr and even Au; these may have reflected the effect of car park and road runoff and/or industrial pollution. Most of these elements (except Mo and Au) and up to 30 others were also routinely detected in sediment samples. Such pollutants as Co, Cu, Ni, Zn and As were detected in bottom sediments of all ponds. There were a number of correlations between pollutants in sediments and the particle's median diameter. However, aggregation leads to large low density flocks and masks correlation of chemicals with SPM particle size. Statistical associations among the elements aided the understanding of their sources and pathways, as well as the underlying biological and abiotic processes. Specifically, our analysis implicated contributions from such sources as allochthonous and autochthonous detritus, roadside and industrial pollution, biologically induced precipitation, and discarded electronics. Elevated levels of Rare Earth Elements (REE) and other trace elements open a possibility of their recovery from the sediments, which should be considered among the multiple benefits of BGI.

This study proposes a novel algorithm based on the multiple self-mixing interference (MSMI) theory to measure the velocity of a remote target without contact. The principle of MSMI is presented and the corresponding formulas for velocity measurement are derived. Fast Fourier transform is applied to detect signal frequency and calculate velocity values. A low-cost, compact, and easy-to-operate experimental setup is also constructed. Experiments are conducted to validate the correctness of our algorithm. This algorithm can improve resolution more easily than conventional self-mixing interference methods.

Lead-free copper halide perovskite nanocrystals (NCs) are emerging materials with excellent photoelectric properties. Herein, we present a colloidal synthesis route of orthorhombic Cs2CuCl4 NCs with well-defined cubic shape and an average diameter of 24 ± 2.1 nm. The Cs2CuCl4 NCs exhibit bright deep blue photoluminescence, which is attributed to the Cu(II) defects. In addition, passivating the Cs2CuCl4 NCs by Ag+ can effectively improve the photoluminescence quantum yield (PLQY) and environmental stability.

Lead-free copper halide perovskite nanocrystals (NCs) are emerging materials with excellent photoelectric properties. Herein, we present a colloidal synthesis route for orthorhombic Cs2CuCl4 NCs with a well-defined cubic shape and an average diameter of 24 ± 2.1 nm. The Cs2CuCl4 NCs exhibited bright, deep blue photoluminescence, which was attributed to the Cu(II) defects. In addition, passivating the Cs2CuCl4 NCs by Ag+ could effectively improve the photoluminescence quantum yield (PLQY) and environmental stability.