Photo-oxidation plays an important role in the lifetime of PLEDs fabricated from PFs. In addition, most of these PLEDs suffer from a degradation of the device under operation; the degradation is documented in the formation of a low-energy emission band at 2.2-2.3 eV, which turns the desired blue emission color into an undesired blue-green emission. With the aim of simultaneously overcoming all these drawbacks, a blue light-emitting polymer/mesoporous silica nanocomposite was prepared by blending poly(9,9-dioctylfluorene) with surface modified nanoporous silica. This nanocomposite film shows dramatically increased photo-stability and color purity.