A nanocrystal composite comprising a) from 0.05 to 7.5% by weight of the total weight of the composite of a plurality of nanocrystals comprising a core comprising a metal or a semiconductive compound or a mixture thereof and at least one ligand, wherein said core is surrounded by at least one ligand, b) a polythiourethane matrix, wherein said polythiourethane matrix is formed by thermal or UV induced nucleophilic addition of polyisocyanates having at least two isocyanate groups and polythiols having at least two thiol groups, wherein said polythiols are selected from the group consisting of wherein n is 2 - 10, R 1 and R 2 are same or different and are independently selected from -CH 2 -CH CH 3 and -CH 2 -CH 2 -SH; wherein R 3, R 4, R 5 and R 6 are same or different and are independently selected from -C -CH 2 -CH 2 -SH, -C -CH 2 -CH CH 3, -CH 2 -C(-CH 2 -O-C -CH 2 -CH 2 -SH) 3 -C -CH 2 -SH, -C -CH -CH 3; wherein R 7, R 8 and R 9 are same or different and are independently selected from -C -CH 2 -CH 2 -SH, -C -CH 2 -CH CH 3, -[CH 2 -CH 2 -O-] o -C -CH 2 -CH 2 -SH, -C -CH 2 -SH, -C -CH -CH 3 and o is 1-10; wherein m is 2-10, R 10, R 11 and R 12 are same or different and independently selected from -CH 2 -CH 2 SH, -CH 2 -CH CH 3, -C -CH 2 -SH, -C -CH -CH 3, and mixtures thereof and wherein said polyisocyanates are selected from polyisocyanates based on isocyanates selected from the group consisting of wherein p, q and r are same or different and have a value 2-10; wherein s, t and u are same or different and have a value 2-10; wherein v has a value 2 - 10; wherein x, y and z are same or different and have a value 2-10, preferably a value 4-6, and more preferably x, y and z are 6; polyisocyanates based on toluene diisocyanate; polyisocyanates based on methylene diphenyl diisocyanate; polyisocyanates based on isophorone diisocyanate; prepolymers based on toluene diisocyanate; prepolymers based on methylene diphenyl diisocyanate; prepolymers based on isophorone diisocyanate, prepolymers based on hexamethylene diisocyanate and mixtures thereof; and wherein said nanocrystals are embedded into said polymer matrix. a) from 0.05 to 7.5% by weight of the total weight of the composite of a plurality of nanocrystals comprising a core comprising a metal or a semiconductive compound or a mixture thereof and at least one ligand, wherein said core is surrounded by at least one ligand, b) a polythiourethane matrix, wherein said polythiourethane matrix is formed by thermal or UV induced nucleophilic addition of polyisocyanates having at least two isocyanate groups and polythiols having at least two thiol groups, wherein said polythiols are selected from the group consisting of wherein n is 2 - 10, R 1 and R 2 are same or different and are independently selected from -CH 2 -CH CH 3 and -CH 2 -CH 2 -SH; wherein R 3, R 4, R 5 and R 6 are same or different and are independently selected from -C -CH 2 -CH 2 -SH, -C -CH 2 -CH CH 3, -CH 2 -C(-CH 2 -O-C -CH 2 -CH 2 -SH) 3 -C -CH 2 -SH, -C -CH -CH 3; wherein R 7, R 8 and R 9 are same or different and are independently selected from -C -CH 2 -CH 2 -SH, -C -CH 2 -CH CH 3, -[CH 2 -CH 2 -O-] o -C -CH 2 -CH 2 -SH, -C -CH 2 -SH, -C -CH -CH 3 and o is 1-10; wherein m is 2-10, R 10, R 11 and R 12 are same or different and independently selected from -CH 2 -CH 2 SH, -CH 2 -CH CH 3, -C -CH 2 -SH, -C -CH -CH 3, and mixtures thereof and wherein said polyisocyanates are selected from polyisocyanates based on isocyanates selected from the group consisting of wherein p, q and r are same or different and have a value 2-10; wherein s, t and u are same or different and have a value 2-10; wherein v has a value 2 - 10; wherein x, y and z are same or different and have a value 2-10, preferably a value 4-6, and more preferably x, y and z are 6; polyisocyanates based on toluene diisocyanate; polyisocyanates based on methylene diphenyl diisocyanate; polyisocyanates based on isophorone diisocyanate; prepolymers based on toluene diisocyanate; prepolymers based on methylene diphenyl diisocyanate; prepolymers based on isophorone diisocyanate, prepolymers based on hexamethylene diisocyanate and mixtures thereof; and wherein said nanocrystals are embedded into said polymer matrix.