A deep study of the optical properties related to the performances in light-emitting diodes (LEDs) of a fluorene-based copolymer containing triphenylamine (TPA), showed a huge reduction of oxidation of the whole material, a macromolecule separation, hence preventing the crystalline aggregation, an improved time-stability of both material chromaticity and morphology compared with commercial poly(9,9-dioctylfluorene) (PFO). LED device prototypes based on this copolymer exploited enhanced performances with respect to commercial PFO prepared under the same conditions.