TECHNOLOGY FOCUS - ELECTRONICS - Preferred Device: The light emitting device comprises a light source, and the light emitting particle-polymer composite is disposed on the light source. In the device, the light emitting particle-polymer composite is disposed in a form of a film, and a remaining space of the optoelectronic device is filled with a resin (preferably the light emitting particle-polymer composite is disposed as a film, and further comprises a resin contacting the light emitting particle-polymer composite). The light emitting device further comprises a transparent plate between the light source and the light emitting particle-polymer composite; and a polymer film at an outer surface, where the polymer film includes the copolymer, the (meth)acrylate-based resin, silicone resin and/or epoxy resin.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The light emitting particle comprises a nanocrystal, a phosphor and/or pigment. The nanocrystal comprises a semiconductor nanocrystal, a metal nanocrystal and/or metal oxide nanocrystal.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The composition further comprises a third monomer having one thiol group located at a terminal end of the third monomer and/or a fourth monomer having an unsaturated carbon-carbon bond located at a terminal end of the fourth monomer. Preferred Components: The first monomer is of formula (R1)k1-L1-(Y1-(SH)m)k2 (I). The second monomer is of formula (R2)k3-L2-(Y2-(X')n)k4 (II). The first monomer and the second monomer are present in combination in an amount of 80-99.9 wt.%. The thiol groups of the first monomer and the unsaturated carbon-carbon bonds of the second monomer are present in a mole ratio of 1:about 0.75 to 1:about 1.25.R1=H, 1-30C alkyl, 6-30C (hetero)aryl, 3-30C (hetero)cycloalkyl, 2-30C alkenyl, 2-30C alkynyl, 3-30C alicyclic group including a ring having a double bond or a triple bond in the ring, 3-30C heterocycloalkyl including a ring having a double bond or a triple bond in the ring (all optionally substituted), 3-30C alicyclic (substituted with 2-30C alkenyl or 2-30C alkynyl), 3-30C heterocycloalkyl (substituted with 2-30C alkenyl or 2-30C alkynyl), hydroxyl, -NH2, 1-30C amine group of formula -NRR' (optionally substituted), isocyanate, isocyanurate, (meth)acrylate, halo, -R'aOR'b or acyl halide of formula -R'c-C(O)X;R and R'=H or 1-30C alkyl,;R'a=1-20C alkylene (optionally substituted);R'b=H or 1-20C alkyl;R'c=alkylene (optionally substituted);X=halo, -C(=O)OR'd, -CN or -C(=O)ONR'eR'f;R'd=H or 1-20C alkyl;R'eR'f=H or 1-20C alkyl;L1=1-30C alkylene, 6-30C (hetero)arylene or 3-30C (hetero)cycloalkylene (all optionally substituted) or single bond;Y1=single bond, 1-30C alkylene or 2-30C alkenylene (where at least one methylene group is replaced by sulfonyl, carbonyl, ether, sulfide, sulfoxide, ester, amide of formula -C(=O)NR'g- or imine of formula -NR'h-);R'g=H or 1-10C alkyl group;R'h=H or 1-10C alkyl;m= greater than or equal to 1;k1=0 to greater than or equal to 1;k2= greater than or equal to 1;m+k2= greater than or equal to 3;X'=1-30C aliphatic organic group including an unsaturated carbon-carbon bond, 6-30C aromatic organic group including an unsaturated carbon-carbon bond or 3-30C alicyclic organic group including an unsaturated carbon-carbon bond;R2=R1;L2=1-30C alkylene, 6-30C (hetero)arylene (all optionally substituted) or single bond;Y2=Y1;n= greater than or equal to 1;k3=0 to greater than or equal to 1;k4= greater than or equal to 1;n+k4= greater than or equal to 3.The m does not exceed the valance of Y1; k1 and k2 does not exceed the valence of the L1; n does not exceed the valance of Y2; and k3 and k4 does not exceed the valence of the L2.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The light emitting particle further comprises a coating, where the coating comprises a polymer having a carboxyl group or its salt. The polymer having a carboxyl group or its salt comprises 1-100 mol.% of a unit including the carboxyl group or its salt. The polymer having a carboxyl group or its salt has a melting point of 50-300 degrees C. The polymer having a carboxyl group or its salt comprises poly(alkylene-co-acrylic acid), poly(alkylene-co-methacrylic acid) or their salts. The polymer having a carboxyl group or its salt is present in an amount of 50-10000 parts by weight. The coated light emitting particle is present as a powder or a film. The polymer is present in an amount of 80-99.9 wt.%. The resin comprises a silicone resin, an epoxy resin, a (meth)acrylate-based resin, the copolymer. SPECIFIC COMPOUNDS - 4 Compounds i.e. 3-mercapto-propionic acid 2,2-bis(3-mercapto-propionyloxymethyl)butyl ester; 3-mercapto-propionic acid 3-(3-mercapto-propionyloxy)-2,2-bis(3-mercapto-propionyloxymethyl)propyl ester; mercaptoacetic acid 3-(2-mercapto-acetoxy)-2,2-bis(2-mercapto-acetoxymethyl)propyl ester; and 3-mercapto-propionic acid 3,5-bis(3-mercapto-propionyloxymethyl)-2,4,6-trioxo-(1,3,5)triazinan-1-ylmethyl ester is specified as the first monomer (I). 3 Compounds i.e. 2,4,6-tris(allyloxy)-(1,3,5)triazine (IA); 1,3,5-triallyl-(1,3,5)triazinane-2,4,6-trione; and 3-allyloxy-2,2-bis(allyloxymethyl)-propan-1-ol is specified as the second monomer (II).    EXAMPLE - Yellow InP/ZnS/InZnS/ZnS nanocrystal was added to chloroform to prepare a solution having an optical density (OD) of 0.027 when measured by diluting the solution by 100 times in toluene. A quantity of the solution (0.9 ml) was mixed with pentaerythritol tetrakis(3-mercaptopropionate) (0.2 g) as a first monomer and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (0.14 g) as a second monomer. Then, the solvent was removed from the solution. Then, the mixture (100 parts by weight) of the first and second monomers were mixed with oxy-phenyl-acetic acid 2-(2-oxo-2-phenyl-acetoxy-ethoxy)-ethyl ester (2 parts by weight). The resulting mixture was polymerized, to prepare a nanocrystal-polymer composite film. The light emitting diodes including the nanocrystal-polymer composite film provided excellent initial efficiency and life-span characteristics.