NOVELTY - Compositions comprises (a) siloxane copolymer (I) and (b) heat-conductive fillers and optionally other ingredients.    USE - The composition is used as a bedding material for solar modules (claimed).    ADVANTAGE - The composition exhibits low hydrophilicity, low water vapor transmission, good handling characteristics, high light reflection, high thermal conductivity, high softness, good adhesion and high electrical disruptive strength. The composition comprises fillers, which increases the reflectivity of the rear side of the module, which does not absorb photons again in the solar cell and are scattered back into the solar cell, thus increasing the output power.    DETAILED DESCRIPTION - Compositions comprises (a) siloxane copolymer of formula (-(A-X-Si(R)(R)-(O-Si(R)(R))n-X-A-C(=O)-NH-Y1-NH-C(=O))a-(Z-D1-Z-C(=O)-NH-Y1-NH-C(=O))b-(A-X-Si(R)(R)-(O-Si(R)(R ))n-X-A-C(=O)-NH-Y1-C(=O)-NH-Y1-NH-C(=O))c-) (I), (b) heat-conductive fillers and optionally other ingredients.    R = monovalent Si-bonded hydrocarbon optionally substituted by halo and interrupted by O;    X = 1-20C alkylene, in which non-adjacent methylene units are replaced by -O-;    A, Z = O or -NR1;    R1 = H or 1-10C alkyl;    Y1 = divalent 1-20C hydrocarbon optionally substituted by halo and interrupted by O;    D1 = bivalent hydrocarbon optionally substituted by halo or 1-6C alkyl, in which the non-adjacent methylene units are replaced by -O-, -COO-, -OCO- or -OCOO-;    n = 1-1000;    a = 1;    b = 1-40; and    c = 1-30.    INDEPENDENT CLAIMS are also included for:    (1) preparing the compositions, comprising mixing the thermally conductive filler and optionally used components (c) to (k) in the siloxane copolymer (a), optionally mixed in the organic solvent (d) at temperature above the softening range of the copolymer; and    (2) embedding the photosensitive layers by laminating the compositions in the form of a film and optionally other embedding materials and a transparent front side and a material for forming the back side of the module and a photosensitive layer.