Abstract Luminescent materials based on the energy transfer effect consist of heteropolyoxometalates of the type K 13[Eu(SiMo x W 11− x O 39) 2] incorporated into xerogel matrices. Results of our experiments suggest that not only the composition parameter x (where x = 1, 3 and 5) of the salts with Eu(III) complex but also the type of the matrix influence the luminescent properties of these materials. The luminescent samples were characterized by such luminescence parameters as emission intensity, luminescence lifetime and quantum yield. The highest emission intensity of Eu(III) ions was exhibited by the salt with x = 1 incorporated into a silicate modified with 3-glycidoxypropyl groups. The longest lifetime was found in the material with a methylated silicate matrix with the same salt. For the complexed Eu(III) ions in these materials there is a correlation between emission intensity changes of the 5D 0 → 7F 2 band and the quantum yield. The materials with a high organic content in matrices such as the silicates with 3-glycidoxypropyl groups (either with closed or opened epoxy cycles) are more thermally unstable and they undergo larger photochemical degradation during exposure on UV radiation than the systems with limited organic content.