TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The organic photoactive polymer is selected from polythiophenes such as poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene), and/or poly(3,4-ethylenedioxythiophene); polyphenylenevinylenes such as poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene, poly(paraphenylenevinylene), and/or ((poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene)-alt-(vinylene) (MDMO-PPV); alternate or statistic conjugated copolymers, comprising at least one benzotriazole unit (B) of formula (Ia) or (Ib), and at least one structural conjugated unit (A), where each unit (B) is connected to at least one unit (A) in any one of the positions 4, 5, 6 or 7 (preferably in positions 4 or 7); alternate pi-conjugated polymers comprising at least one electron-acceptor fluoroarylvinylidene unit (A1) of formula (III); and at least one electron-donor conjugated structural unit (B1), connected to the unit (A1) in the points a' indicated as dotted lines in formula (III); copolymers based on acridonic units, comprising one monomeric unit (A2) of formula (IV), and at least one monomeric unit (B2) of formula (V) connected at any available position of a side heteroaromatic ring of the unit (A2) through one of the two positions a'1 indicated as dotted lines in formula (V); alternate conjugated copolymers comprising benzothiadiazole units such as PCDTBT (poly(N-9''-heptadecyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)), or PCPDTBT (poly(2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta(2,1-b;3,4-b')-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole))); alternate conjugated copolymers comprising thieno(3,4-b)pyrazidinic units; alternate conjugated copolymers comprising quinoxaline units; and alternate conjugated copolymers comprising monomeric silole units such as copolymers of 9,9-dichloro-9-silafluorene; and alternate conjugated copolymers comprising condensed thiophene units such as copolymers of thieno(3,4-b)thiophene and of benzo(1,2-b:4,5-b')dithiophene (preferably organic photoactive polymer is P3HT, or a polymer selected from 11 polymers as given in the specification e.g. polymers of formulae (Ia1), or (Ia2)).R'=alkyl, aryl, or (thio)acyl (all optionally substituted);X 1to X 5=H, fluoro group (preferably F or -CF 2R' a), or 1-12C alkyl;R' a=H, F, or optionally fluorinated 1-10C hydrocarbyl;a'=point of attachment of electron-donor conjugated structural unit to electron-acceptor fluoroarylvinylidene unit of formula (III);X'=S, or Se;Y'=O, S, or -NR' c'R' band R' c=1-24C organic substituents selected from alkyl or aryl (both optionally substituted), or (thio)acyl;Z'=O, S, Se, or -NR' d;R' d=1-24C organic substituent selected from alkyl, or aryl (both optionally substituted), or (thio)acyl;a'1=point of attachment of monomeric unit of formula (V) to monomeric unit of formula (IV);R' e=linear or branched 1-20C alkyl;n=2-500.Provided that: at least one of the X 1to X 5substituents is F, or a -CF 2R' a.Preferred Composition: The photoactive composition (C1) comprises the naphthalene diimide compound (I) (0.1-18, preferably 1-15) wt.% with respect to the weight of the photoactive organic polymer. Preferred Definitions:    R 1and R 2=7C alkyl;    R' 1, R' 2, R 3, R 5to R 8, R 10, R 12, and R 14to R 17=H;    R 4, R 11, and R 20=H, or 6C alkyl;    R 9, R 13and R 18=6C alkyl.    Provided that:    (1) when R 1and R 2are 7C alkyl, and R' 1, R' 2, R 3, R 4, R 12, R 13are H, then d and e are 1, and a to c and f to h are 0;    (2) when R 1and R 2are 7C alkyl, and R' 1, R' 2, R 3to R 6, and R 12to R 15are H, and R 11and R 20are 6C alkyl, then c to f are 0, and a, b, g and h are 1; and    (3) when R 1and R 2are 7C alkyl, and R' 1, R' 2, R 3, R 5to R 8, R 10to R 12, R 14to R 17, R 19, and R 20are H, and R 4, R 9, R 13and R 18are 6C alkyl, then a to h are 1.    SPECIFIC COMPOUNDS - 2 Compounds i.e. 2,6-bis(2'-thienyl)-N,N'-diheptyl-1,4,5,8-tetracarboxy-naphthalene diimide of formula (I'a), and 2,6-bis(5''-hexyldithien-2'-yl)-N,N'-diheptyl-1,4,5,8-tetracarboxynaphthalene diimide, are disclosed as the compound (I').    EXAMPLE - For preparing photoactive composition, poly(3-hexylthiophene) (P3HT) (8.4 mg), and 2,6-bis(2'-thienyl)-N,N'-diheptyl-1,4,5,8-tetracarboxy-naphthalene diimide (5%, 0.4 mg) were dissolved in chloroform (290 microl). The solution was kept under stirring for 17 hours at 40 degrees C. The solution thus obtained was used for preparing a film having a thickness of 0.83 microns by spin coating. The mobility values of the film indicated high mobility of electronic holes of about -1.7x 10 -5 Delta B (second).