A Novel Crow Swarm Optimization Algorithm (CSO) Coupling Particle Swarm Optimization (PSO) and Crow Search Algorithm (CSA).

The balance between exploitation and exploration essentially determines the performance of a population-based optimization algorithm, which is also a big challenge in algorithm design. Particle swarm optimization (PSO) has strong ability in exploitation, but is relatively weak in exploration, while crow search algorithm (CSA) is characterized by simplicity and more randomness. This study proposes a new crow swarm optimization algorithm coupling PSO and CSA, which provides the individuals the possibility of exploring the unknown regions under the guidance of another random individual. The proposed CSO algorithm is tested on several benchmark functions, including both unimodal and multimodal problems with different variable dimensions. The performance of the proposed CSO is evaluated by the optimization efficiency, the global search ability, and the robustness to parameter settings, all of which are improved to a great extent compared with either PSO and CSA, as the proposed CSO combines the advantages of PSO in exploitation and that of CSA in exploration, especially for complex high-dimensional problems.

Water-induced fluorescence enhancement of lead-free cesium bismuth halide quantum dots by 130% for stable white light-emitting devices.

Recently, the discovery and development of lead-free perovskite quantum dots (QDs) that are eco-friendly and stable has become an active research area in low-cost lighting and display fields. However, the low photoluminescence quantum yield (PLQY) caused by the residual surface states of such QDs severely hinders their practical applications and commercialization. In this work, a strategy of employing water-induced nanocomposites was proposed to improve the PLQY of cesium bismuth halide (Cs3Bi2X9) QDs, and a substantial enhancement by ∼130% (from 20.2% to 46.4%) was achieved by an optimized water treatment of Cs3Bi2Br9 QDs. A detailed analysis indicated that Cs3Bi2Br9/BiOBr nanocomposites, in which the Cs3Bi2Br9 QD core was encapsulated into a BiOBr matrix, can effectively suppress the surface defects of QDs, resulting in a longer PL lifetime and a larger exciton binding energy compared with the pristine sample. Finally, the Cs3Bi2Br9/BiOBr nanocomposites were used as the color-converting phosphors for down-conversion white light-emitting devices, which show a good operation stability in ambient air, significantly better than the reference device constructed with conventional lead-halide perovskites. We believe that the method used here provides an effective strategy to improve the fluorescence efficiency of lead-free perovskite QDs, which will create opportunities for their applications in lighting and displays.

Silica coating enhances the stability of inorganic perovskite nanocrystals for efficient and stable down-conversion in white light-emitting devices.

Recently, inorganic halide perovskite (CsPbX3, X = Cl, Br, I) quantum dots (QDs) have attracted tremendous research interests because of their great potential for application in the fields of low-cost light sources and displays. However, the unsatisfactory structural and chemical stabilities of such materials are the main obstacles hindering reliable device operation significantly. In this study, we successfully prepared CsPbBr3/silica QD composites through a simple sol-gel reaction by using tetramethoxysilane as a single molecule precursor. The as-prepared CsPbBr3/silica QD composites demonstrated substantially improved stability against heat, light, and environmental oxygen/moisture. Besides, a relatively narrower photoluminescence linewidth and higher quantum yield were achieved compared with that of fresh CsPbBr3 QDs. Furthermore, the CsPbBr3 QDs/silica composites were applied as color-converting layer curing on blue light-emitting diodes (LEDs) for white LED applications. Finally, a high power efficiency of 63.5 lm W-1 was obtained and the light emission could be efficiently sustained over 13 h without any decay in the continuous current mode, demonstrating remarkable operation stability than that reported previously. It can be anticipated that the excellent properties and facile processing technique used here will make perovskite QDs/silica composites attractive for applications in optoelectronics and industrial fields.