▎ 摘　　要

NOVELTY - Preparation of halide perovskite nanocrystal involves preparing raw materials including first source, second source and third source by light control method. The first source is selected from compound containing first element, and compound containing first group and first element. The first element is selected from one or more of lithium, sodium, potassium, rubidium and cesium. The first group is selected from methylamine and/or formamidine. The second source is selected from compound containing second element and a simple substance of second element. The second element is selected from one or more of lead, tin, cadmium, manganese, zinc, nickel, calcium, strontium, barium, germanium, magnesium, calcium, copper, bismuth, silver, europium, antimony and indium. USE - Preparation of halide perovskite nanocrystal used for preparing composite material for solar cells, light-emitting diodes, photoelectric detection, nanocatalysis, biosensing and nanophotonics (all claimed). ADVANTAGE - The halide perovskite nanocrystals have excellent stability and dispersibility, fluorescence quantum yield of 30-80% and uniform morphology and size, and can realize full visible spectrum of 400-700 nm. The preparation method has the advantages of simple process, short time consumption, low cost, easy amplification and synthesis. DETAILED DESCRIPTION - Preparation of halide perovskite nanocrystal involves preparing raw materials including first source, second source and third source by light control method. The first source is selected from at least one of a compound containing first element, and a compound containing first group and first element. The first element is selected from one or more of lithium, sodium, potassium, rubidium and cesium. The first group is selected from methylamine and/or formamidine. The second source is selected from at least one of a compound containing second element and a simple substance of second element. The second element is selected from one or more of lead, tin, cadmium, manganese, zinc, nickel, calcium, strontium, barium, germanium, magnesium, calcium, copper, bismuth, silver, europium, antimony and indium. The compound containing first element includes a compound containing first element but not second element, and a compound containing both first and second elements. The compound containing second element includes a compound containing second element but not first element, and a compound containing both first and second elements. The compound containing first element but not second element may be at least one of carbonate, acetate, oleate, stearate, oxide, hydroxide, nitrate, sulfate, oxalate, borate, vanadate, tungstate, molybdate, and chromate, preferably at least one of acetate and carbonate containing first element but not containing second element. The first group-containing compound is selected from methylamine group-containing compound and/or formamidine group-containing compound. The compound containing second element but not first element may be at least one of acetate, carbonate, oleate, stearate, oxide, hydroxide, acid salt, sulfate, oxalate, borate, vanadate, tungstate, molybdate, and chromate, preferably at least one of acetate and oxalate containing second element but not containing first element. The first source and second source may be a compound containing both first and second elements. The compound containing both first and second elements is selected from at least one of cesium-lead oxide (Cs2PbO2), ruthenium-lead oxide (Ru2PbO2), cesium-tin oxide (Cs2Sn2O3), ruthenium-tin oxide (Ru2SnO2), ruthenium-tin oxide (Ru2Sn2O3), cesium-cadmium fluoride (CsCdF3) or ruthenium-cadmium fluoride (RuCdF3). The third source is a halogenated hydrocarbon containing third element, and third element is halogen. The third source is one or more of halogenated hydrocarbons containing chlorine, bromine and iodine elements. The third source is one or more of monochloromethane, dichloromethane, chloroform, carbon tetrachloride, chloroethane, 1,2-dichloroethane, dibromomethane, bromoisopropane, iodonium, isopropane and diiodomethane. INDEPENDENT CLAIMS are included for:(1) a composite material, which comprises the halide perovskite nanocrystal, where the composite material includes a matrix and the halide perovskite nanocrystals. The halide perovskite nanocrystals are located within and/or on surface of the matrix. The composite material includes a matrix and halide perovskite nanocrystals grown in the matrix. The matrix is selected from one or more of mesoporous silica, mesoporous titanium dioxide, mesoporous alumina, glass-ceramic, zinc sulfide, graphene, zeolite and metal organic framework materials, preferably mesoporous silica. The percentage of the halide perovskite nanocrystals in the mass of the composite material is 1% or more and less than 100%. The composite material has at least one dimension in the range of 1-1000 nm, preferably 2-500 nm. The composite nanomaterial can be cesium-lead halide-doped mesoporous silica (CsPbX3@mSiO2), methylamine-lead halide-doped mesoporous silica (CH3NH3PbX3@mSiO2), formamidine-lead halide-doped mesoporous silica (FAPbX3@mSiO2), metal-lead halide-doped mesoporous silica (APbX3@mSiO2) and cesium-boron halide-doped mesoporous silica (CsBX3@mSiO2), preferably at least one of CsPb(Clx/Bry)@mSiO2, CsPb(Brx/Iy)@mSiO2, CH3NH3Pb(Clx/Bry)@mSiO2, CsPb(Brx/Iy)@mSiO2, FAPb(Clx/Bry)@mSiO2, FAPb(Brx/Iy)@mSiO2, (Csx/Ruy)PbX3@mSiO2, and Cs(Pbx/Mny)X3@mSiO2; and (2) preparation of the composite material, which involves: (a) preparing the halide perovskite nanocrystal by mixing dissolving first source and second source in a surfactant and/or in a solvent containing a surfactant in an inert atmosphere, to obtain a mixed solution, mixing the mixed solution with matrix, separating solid substance in separated liquid subjected to photo-controlled reaction with third source, stirring the mixed solution for 1-24 hours to promote adsorption of first ions and second ions in the matrix, where the mass ratio of the matrix to the halogenated hydrocarbon is 1:(103-107), preferably 1:(104-106); (b) performing solid-liquid separation on reaction system to obtain a solid substance after the stirring reaction is completed, washing obtained solid from solid-liquid separation to remove first ions and second ions remaining on surface of substrate, where the washing solvent is an organic solvent, e.g. at least one of acetone, acetonitrile, n-butanol, isopropanol, tert-butanol, diethyl ether, methyl ethyl ketone, octane, cyclohexane and toluene, preferably acetone and/or cyclohexane, and the washing method can be filtration washing or centrifugal washing. X=at least one of chloride, bromide and iodide; x+y=3; and x,y=0-3, preferably 0, 1, 1.5, 2 or 3.