The present disclosure relates to a perovskite sheet that includes two outer layers, each including AX; and a first layer that includes BX.sub.2, where B is a first cation, A is a second cation, X is a first anion, X is a second anion, and the first BX.sub.2 layer is positioned between the two outer layers.

A fluorescent material includes at least one fluorescent compound having a structure formula of ABX.sub.ZY.sub.3-Z as defined in the specification, a plurality of NH.sub.3.sup.+ group-containing ions bound to the fluorescent compound through protonation of amine groups of an amine composition, and a plurality of COO.sup. group-containing ions bound to the fluorescent compound through deprotonation of carboxyl groups of an acid composition. The amine composition has a total hydrogen bonding Hansen solubility parameter (T.sub.H) ranges from 2.4 to 3.3 (cal/cm.sup.3).sup.1/2, and the acid composition has a total polar Hansen solubility parameter (T.sub.P) which is less than 1.4 (cal/cm.sup.3).sup.1/2.

A method for producing a photoresponsive nanoparticle. The method includes a first step of continuously transporting a first raw material liquid containing a lead halide and a second raw material liquid containing a fatty acid cesium to a heated mixer through a transport path, and a second step of mixing the first raw material liquid and the second raw material liquid.

Described herein are compositions and methods relating to luminescent structures.

A luminescent composite material and a preparation method therefor. The luminescent composite material is prepared by mixing a precursor of a quantum dot and an oxide or a precursor thereof followed by high-temperature calcination. Compared with traditional methods, the method provided herein is a simple and low-cost synthesis process without using solvents, and is suitable for large-scale production. The luminescent composite material has high quantum efficiency, luminous intensity and luminous color purity and good photothermal stability, which can provide basis for theoretical research and applications of the luminescent composite material in high-performance photoluminescence devices, lasers and nonlinear optical devices.

A solvent-free and ligand-free ball milling method for preparation of cesium lead tribromide (CsPbBr.sub.3) quantum dot is provided. First, mixing a Cs source, a Pb source, and a Br source as per a molar ratio of Cs source:Pb source:Br source is 1:1?6:1?9, and then adding polymethyl methacrylate (PMMA) to obtain a mixture. The mixture is milled for 1-2 hours at a rotation speed in a range of 360?630 revolutions per minute (r/min) in a ball milling device, obtaining CsPbBr.sub.3 quantum dot. The method has advantages such as simple process, easy industrial production, no solvent, no organic ligand, low cost, and environmental protection. A quantum yield of product obtained by the method is up to 78%, and the product has a strong environmental stability. A preparation temperature of the product is low, and the reaction can be completed at a room temperature without a high temperature treatment.

This disclosure relates to an environmental-friendly and cost-efficient approach to synthesize CsPbBr.sub.3 powders in a large scale at room temperature with water. Using ultrasonication and centrifugation, CsPbBr.sub.3 nanocrystals can be obtained with green (?522 nm) and blue (?493 nm) emissions from the powders. The photoluminescence quantum yield of the blue-emitting nanocrystals is 80%, which is much larger than 61.4% of the CsPbBr.sub.3 nanocrystals made by an anti-solvent method. The green-emitting nanocrystals exhibit better stability than those made by the anti-solvent method over a period of 9 days. The method opens a new avenue to potentially produce inorganic and/or inorganic-organic hybrid halide perovskite nanocrystals without harmful organic solvents used in precursor solutions.

A method of producing perovskite nanocrystalline particles using a liquid crystal includes a first operation for preparing a mixed solution including a first precursor compound, a second precursor compound, and a first solvent. a second operation for preparing a precursor solution by adding an organic ligand to the prepared mixed solution, a third operation for performing crystallization treatment after adding the prepared precursor solution to a reactor containing a liquid crystal, and a fourth operation for separating the perovskite nanocrystalline particles from the crystallized solution through a centrifugal separator.

Bandgap-tunable perovskite compositions are provided having the formula CsPb(A).sub.xB.sub.y).sub.3, wherein A and B are each a halogen. The mixed halide perovskite composition has a morphology which suppresses phase segregation to stabilize a tuned bandgap of the mixed halide perovskite composition. For example, the perovskite may be in the form of nanocrystals embedded in a non-perovskite matrix, which, for example, may have the formula Cs.sub.4Pb(A).sub.xB.sub.y)6, wherein A and B are each a halogen. Solar cells and light-emitting diodes comprising the mixed perovskite compositions are also provided.

Provided are perovskite nanocrystalline particle and an optoelectronic device using the same. The perovskite nanocrystalline particle may include a perovskite nanocrystalline structure while being dispersible in an organic solvent. Accordingly, the perovskite nanocrystalline particle in accordance with the present invention has therein a perovskite nanocrystal having a crystalline structure in which FCC and BCC are combined; can form a lamellar structure in which an organic (or A site) plane and an inorganic plane are alternately stacked; and can show high color purity since excitons are confined to the inorganic plane.