The invention relates to copolymer complexes of the formula (I): wherein [A x -[B(C) y -D Z ] denotes a single unit of the copolymer complex that is repeated n times, wherein n is an integer greater than one, and wherein the single unit comprises a conjugated backbone coordinated to a complex (C) comprising rare earth metal(s); x, y and z are numbers greater than zero such that x = y+z ; A is independently selected from a group consisting of: fluorene, carbazole, oxadiazole, triphenylamine or derivatives thereof; B is a functional ligand selected from the group consisting of: benzoic acid, 1,3-diphenylpropane-1,3-dione, 1,10- phenanthroline, 2,2-bipyridine, or derivatives thereof; and D is independently selected from a group consisting of: fluorene, carbazole, oxadiazole, triphenylamine or derivatives thereof.