NOVELTY - S,S-dioxo-dibenzothiophene unit-containing electron donor polymer (I) is new.    USE - (I) is useful in organic solar cells and organic field-effect transistor devices (claimed).    ADVANTAGE - (I): contains S,S-dioxo-dibenzothiophene unit, which has higher electronegativity; and has deeper highest occupied molecular orbital level, strong inter-molecular interactions, high absorption coefficient, high mobility, and high optical response properties.    DETAILED DESCRIPTION - S,S-dioxo-dibenzothiophene unit-containing electron donor polymer of formula (I) is new.    x = more than 0 and not less than 1;    y = not greater than 0 and less than 1;    x+y = 1;    n = 1-300;    R = H, F, alkoxy or polar group-terminated alkoxy chain;    polar group = amine group, phosphate group or cyano group;    G = thiophene group of formula (II), furan group of formula (III), selenophene group of formula (IV), phenylene group of formula (V), thieno(3,2-b)thiophene group of formula (VI), 4H-cyclopenta(2,1-b:3,4-b')dithiophene group of formula (VII), 4H-dithieno(3,2-b:2',3'-d)pyrrole group of formula (VIII), 7H-3,4-dithia-7-sila-cyclopenta(a)pentalene group of formula (IX), 5H-dibenzo(b,d)silole group of formula (X), carbazole group of formula (XI), benzo(1,2-b:4,5-b')dithiophene group of formula (XII), benzo(1,2-b:4,5-b')difuran group of formula (XIII), 5,11-dihydroindolo(3,2-b)carbazole group of formula (XIV), 6,12-dihydroindeno(1,2-b)fluorene group of formula (XV), 9,18-diazapentacyclo(10.6.0.0(3,10).0(4,8).0(13,17))octadeca-1,3(10),4(8),6,11,13(17),15-heptaene group of formula (XVI), 5,14-dithiapentacyclo(10.6.0.0(3,10).0(4,8).0(13,17))octadeca-1,3(10),4(8),6,11,13(17),15-heptaene group of formula (XVII), 5,14-diselenapentacyclo(10.6.0.0(3,10).0(4,8).0(13,17))octadeca-1,3(10),4(8),6,11,13(17),15-heptaene group of formula (XVIII) or 5H-dithieno(3,2-b:2',3'-d)pyran group of formula (IXX);    R1, R2 = 1-30C alkyl group (with at least one carbon atom is replaced by oxygen atom), alkenyl, alkynyl, aryl, hydroxy, amino, carbonyl group, nitro, phenyl, substituted thienyl (all are optionally substituted with halo) or H;    A = nitrogen-containing fused heterocyclic groups of formulae (XX)-(XXII), 4H-thieno(3,4-c)pyrrole-4,6(5H)-dione groups of formula (XXIII), 3,6-di(thiophen-2-yl)-1H-thieno(3,4-c)pyrrole-1,4(5H)-dione groups of formula (XXIV), (E)-1H,1'H-(3,3')biindolylidene-2,2'-dione groups of formula (XXV), thieno(3,4-b)thiophene-2-carboxylate groups of formula (XXVI), 2-(sulfonyl)thieno(3,4-b)thiophene groups of formula (XXVII), thieno(3,4-b)pyrazine groups of formula (XXVIII) or quinoxaline groups of formula (IXXX);    X1, X2 = N, O, S or Se;    X3 = H or F;    R3, R4 = H, F or 1-30C alkoxy; and    R5 = 1-30C alkyl or alkylphenyl.