TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The group existing in the terminal of divalent organic group is group containing fullerene derivative residue, or group containing naphthalene imide derivative residue or perylene imide derivative residue.    TECHNOLOGY FOCUS - POLYMERS - Preparation (disclosed): A core portion-containing compound of formula (a) is reacted with divalent organic group-containing compound of formula: V2-T(-L-Z)-L-Z, to obtain a trivalent organic group-containing compound of formula (b). The obtained trivalent organic group-containing compound (b) is reacted with active functional group-containing compound of formula: V3-Y', to obtain a branched compound of formula (c).X=core portion;W2,W3,V2,V3=active functional group;h=2 or more;Z=protecting group;andY'=group existing in terminal of divalent organic group.Preferred Component: The divalent organic group and trivalent organic group-containing repeating unit (1) has bonded with the core portion by trivalent organic group. The core portion, and divalent organic group and trivalent organic group are conjugating as a whole. The core portion is a divalent organic group of formula (1a). The divalent organic group and trivalent organic group-containing repeating unit (1) is of formula (1b).Ar2=optionally substituted (bivalent heterocyclic group or bivalent aromatic hydrocarbyl);R6-R9=optionally substituted (monohydric heterocyclic group or aryl), H, alkyl, or alkoxy, where hydrogen atom of one portion or whole portion in the group is optionally substituted by fluorine atom;p-r=0-10, where sum of p, q and r is 2-20;R10,R11=H, alkyl, or aryl, where hydrogen atom of one portion or whole portion in the group is optionally substituted by fluorine atom;andk=3-10. Preferred Definitions:    L=divalent organic group of formula (2);    Ar1=same as Ar2;    R1-R4=same as R6;    m-o=0-10, where at least one of m and o is 1 or more, and sum of m, n and o is 2-16;    T=trivalent organic group of formula (3-7);and    R5=H, alkyl, aryl or cyano.    EXAMPLE - Benzo(de)isoquinoline-1,3-dione-containing compound of formula (I) (in mg) (760), 3,5-diiodobromobenzene (89) and dry toluene (7 ml) were added and heat-dried. Then, tetrakis(triphenylphosphine)palladium(0) (19) was added to the resulting mixture and refluxed under argon atmosphere for 12 hours. The solid substance was removed and evaporated under reduced pressure, and the resulting mixture was purified using silica gel and chloroform by column chromatography, to obtain 2-(3-bromo-5-thien-2-ylphenyl)thiophene-containing compound of formula (II). The obtained 2-(3-bromo-5-thien-2-ylphenyl)thiophene-containing compound (II) (292), bis-tributylstannyl-tetra-thiophene (55) and dry toluene (1.2 ml) were added and heat-dried. Then, tetrakis(triphenylphosphine)palladium(0) (5) was added to the resulting mixture and refluxed under argon atmosphere for 8 hours. The solid substance was removed and evaporated under reduced pressure, and the resulting mixture was purified using alumina and chloroform by column chromatography, to obtain 2,2':5',2"-terthiophene-containing branched compound of formula (III).    A=group of formula (IIa);    B'=group of formula (IIIa);and    D=group of formula (IIIb).