TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The stabilized photoactive composition comprises: at least one fullerene (Cx) (where x is 50-250); at least one carbon nanotube; at least one antioxidant; at least one sterically hindered amine. Preferred Components: The photoactive organic polymer is: polythiophenes such as poly(3-hexylthiophene), poly(3-octylthiophene) and/or poly(3,4-ethylenedioxythiophene); polyphenylenevinylenes such as poly(2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylenevinylene, poly(paraphenylenevinylene) and/or (poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene)-alt(vinylene)); alternating conjugated polymers comprising naphthalene diimide units (A1) of formula (I) and at least one conjugated electron-donor structural unit (A2), in which the unit (A1) is connected to the unit (A2), in the alternating copolymer, in any of the positions 2, 3, 6 or 7; alternating or statistic conjugated copolymers comprising at least one benzotriazole unit (B1) of formula (IIa) or (IIb), and at least one conjugated structural unit (B2), where each unit (B1) is connected to at least one unit (B2) in any of the positions 4, 5, 6 or 7; alternating pi -conjugated polymers comprising at least one fluoroarylvinylidene electron acceptor unit (C1) of (III) and at least one conjugated electron-donor structural unit (C2) connected to unit (C1); copolymers based on acridone units comprising one monomeric unit (D1) of formula (IV) and at least one monomeric unit (D2) of formula (V), where the monomeric unit (D2) is connected to any available position of a heteroaromatic side-ring of unit (D1) through one of the two positions indicated by dashed lines in (V); alternating conjugated copolymers comprising benzothiadiazole units such as poly(N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)), (poly(2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta-(2,1-b;3,4-b')-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole))); alternating conjugated copolymers comprising thieno(3,4-b)pyrazine units; alternating conjugated copolymers comprising quinoxaline units; alternating conjugated copolymers comprising silole monomeric units such as copolymers of 9,9-dialkyl-9-silafluorene; and/or alternating conjugated copolymers comprising condensed thiophene units such as copolymers of thieno(3,4-b)thiophene and benzo(1,2-b:4,5-b')dithiophene. The photoactive organic polymer is poly(3-hexylthiophene) (preferred) or polymers of formulae (P1)-(P13). The polyhedral oligomeric silsesquioxanes are of formulae (S1)-(S4).R, R1 = 1-36C alkyl or aryl (optionally substituted by 1-24C alkyl);R1 = alkyl, aryl, acyl or thioacyl (all optionally substituted);X1-X5 = H, F, 1-12C alkyl or -CF2R2;R2 = H, F, or 1-10C hydrocarbyl (optionally fluorinated);X = S or Se;Y1 = O, S or NR2;R3, R2 = 1-24C alkyl (optionally substituted), 1-24C aryl, 1-24C acyl or 1-24C thioacyl;Z1 = O, S, Se or NR3;R3 = 1-24C alkyl, 1-24C aryl (both optionally substituted), 1-24C acyl or 1-24C thioacyl;p/q = 0,59;R10 = 1-20C alkyl;Y3 = -R10 or -OR10;r+s = 1;r, s = greater than 0.1;n = 2-500;R1 = H, 1-20C alkyl (optionally substituted by at least one halo), 3-8C cycloalkyl, aryl, alkyl or aryl or N-alkylaryl or cycloalkylamine, epoxy, carboxy, amide, (meth)acrylate, olefin, siloxane moiety of formula (-O-Si(R3)2R4), or 1-20C alkyl, alkenyl or cycloalkenyl, alkyl or cycloalkyl containing at least one O or OH, or polyethylene glycol moiety of formula (-CH2-CH2-(O-CH2-CH2)t-O-CHR5R6);R3 = 1-20C alkyl;R4 = H;t = 1-20;R5, R6 = H, 1-20C alkyl (optionally substituted by halo), 3-8C cycloalkyl, -O-N+(R7)4;R7 = 1-20C alkyl; andR2 = R1 or 1-20C alkyl (optionally substituted by at least one CN), mercaptoalkyl, hydroxyalkyloxy-(aryloxy-sulfonic acids)-aklyl, diol, imide or nonbornenyl, or alkaline metal, preferably lithium in formula (S2), preferably R1 and R2 are both isobutyl in formula (S1), and R1 is isobutyl or isooctyl and R2 is OH in formula (S2) .Provided that, at least one of X1-X5 is fluorine. The UV stabilizer is present in the stabilized photoactive composition at 0.05-3 wt.% with respect to the total weight of the photoactive organic polymer. The fullerene comprises derivatives of fullerene (C60 or C70), preferably (6,6)-phenyl-C61-methylbutyrate or phenyl-C71-methylbutyrate. The weight ratio between the fullerene and the photoactive organic polymer is 1:4-4:1. The weight ratio between the carbon nanotube and the photoactive organic polymer is 1:6-3:1. The antioxidant is present in the stabilized photoactive composition at 0.005-3 wt.% with respect to the total weight of the photoactive organic polymer. The sterically hindered amine is present in the stabilized photoactive composition at 0-3 wt.% with respect to the total weight of the photoactive organic polymer. EXAMPLE - Poly(3-hexylthiophene) (15 mg) was dissolved in 1 ml of 1,2-dichlorobenzene to obtain a solution A1. TriSilanolPhenyl POSS (RTM: Polyhedral oligomeric silsesquioxane) (1.5 mg) was dissolved in 1 ml of 1,2-dichlorobenzene to obtain solution B1. Then 990 mu l of solution A1 and 10 mu l of solution B1 were subsequently mixed to obtain a solution in 1,2-dichlorobenzene of poly(3-hexylthiophene) and TriSilanolPhenyl POSS (RTM: Polyhedral oligomeric silsesquioxane) i.e. the stabilized photoactive composition.