TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The method further involves forming a shell of primary semiconductor nanocrystals on the surface of secondary nanocrystals to obtain core-shell nanocrystals. Preferred Composition: The organic solvent is hydrophobic solvent chosen from 6-22C primary alkyl amine, 6-22C secondary alkyl amine, 6-40C tertiary alkyl amine, heterocyclic compound having nitrogen atom, 6-40C aliphatic hydrocarbon, aromatic hydrocarbon substituted with 6-30C alkyl group, phosphine substituted with 6-22C alkyl group, phosphine oxide substituted with 6-22C alkyl group and 12-22C aromatic ether. The metal precursor is chosen from 81 metal precursors e.g. dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc nitrate, zinc oxide, zinc peroxide, cadmium acetate, cadmium acetylacetonate, cadmium iodide, mercury acetate, mercury iodide, lead oxide, lead nitrate, lead sulfate, tin acetate, tin bis(acetylacetonate), gallium oxide, indium hydroxide and thallium chloride. The non-metal precursor is chosen from hexanethiol, octanethiol, decanethiol, dodecanethiol, hexadecanethiol, mercaptopropylsilane, sulfur-trioctylphosphine, sulfur-tributylphosphine, sulfur-triphenylphosphine, sulfur-trioctylamine, trimethylsilylsulfur, ammonium sulfide, sodium sulfide, selenium-trioctylphosphine, selenium-tributylphosphine, selenium-triphenylphosphine, tellurium-tributylphosphine, tellurium-triphenylphosphine, tris(trimethylsilyl)phosphine, tris(dimethylamino)phosphine, triethylphosphine, tributylphosphine, trioctylphosphine, triphenylphosphine, tricyclohexylphosphine, arsenic oxide, arsenic chloride, arsenic sulfate, arsenic bromide, arsenic iodide, nitric oxide, nitric acid and ammonium nitrate. The metal precursor comprises metal chosen from group-II metal, group-III metal and group-IV metal. The non-metal precursor is compound comprising an element chosen from group-V element and group-VI element. The ionic liquid is chosen from (un)substituted imidazolium salt, (un)substituted pyrazolium salt, (un)substituted triazolium salt, (un)substituted thiazolium salt, (un)substituted oxazolium salt, (un)substituted pyridazinium salt, (un)substituted pyrimidinium salt, (un)substituted ammonium salt, (un)substituted phosphonium salt, (un)substituted sulfonium salt, (un)substituted pyridinium salt, and (un)substituted pyrrolidinium salt. The ionic liquid comprises halide anion, tetrafluoroborate anion, hexafluorophosphate anion, perchlorate anion, acetate anion, trifluoroacetate anion, triflate anion, hydrogen sulfate anion, alkyl sulfate anion, sulfite anion, hydrogen sulfite anion, chloroaluminate anion, tetrabromoaluminate anion, nitrite anion, nitrate anion, dichlorocuprate anion, phosphate anion, hydrogen phosphate anion, dihydrogen phosphate anion, carbonate anion, hydrogen carbonate anion, sulfonate anion, tosylate anion, and bis(trifluoromethylsulfonyl)imide anion. The content of ionic liquid is 40 vol.% with respect to total volume of the organic solvent. The content of protic solvent is 0.01 vol.% or more of total volume of the ionic liquid. The protic solvent comprises amine having 6 or more carbon atoms and/or alcohol having 6 or more carbon atoms. The amine comprises monoamine, diamine and/or triamine. The alcohol comprises monoalcohol, dialcohol, trialcohol and/or polyol. The ligand compound comprises compound of formulae: RCOOH (I), RNH2 (II), R2NH (III), R3N (IV), RSH (V), R3PO (VI), R3P (VII), ROH (VIII) and RCOOR' (IX).R,R'=1-24C alkyl or 5-20C aryl.Preferred Property: The core-shell nanocrystals have quantum yield of 50% or more.