TECHNOLOGY FOCUS - POLYMERS - Preparation (disclosed): Naphthalene derivative of formula (A) is subjected to condensation polymerization in presence of catalyst and base in an organic solvent, to obtain high-molecular compound. Preferred Composition: The naphthyl group-containing repeating unit (I) is preferably of formula (II)-(IV). The high-molecular compound further has repeating unit of formula: -(Y')- (V).X21,X22,X31,X32,X41,X42=chalcogen, preferably sulfur, selenium or oxygen;R23-R28,R43-R48,R33-R38=H, alkyl, alkoxy, alkylthio, monovalent heterocyclic group, aryl, aryloxy, arylthio, arylalkyl, aryl alkoxy, aryl alkylthio, substituted silyl, optionally substituted carboxy, cyano or fluoro;Y'=bivalent group having metal complex structure, ethynylene, arylene, or bivalent heterocyclic group (all optionally substituted), preferably of formula: -(T)- or group (a);T=optionally substituted bivalent heterocyclic group;n=2-8;Ar3,Ar4=Ar1;andR71,R72=R23.Preferred Property: The difference of the value of the energy level of a lower occupied molecular orbital and value of the energy level of the highest occupied molecular orbital of aromatic group having electron-accepting property in the naphthyl group-containing repeating unit (I) is 4.4 eV or less. Preferred Definitions:    Ar1,Ar2=heterocyclic 5-membered ring.    EXAMPLE - Chlorobenzene (20 ml) was deaerated in nitrogen atmosphere, chloroform solution of tris(dibenzylideneacetone)dipalladium(0) (in mg) (4), tri(o-tolyl)phosphine (5), 5,5'-dibromo-4,4'-didodecyl-2,2'-bithiophene (132), and 2,7-bis-trimethylstannanyl-3,8-dithia-dicyclopenta(a,f)naphthalene (114) and chlorobenzene were added to the reaction mixture, stirred for three days, refluxed, the reaction solution was poured into the mixed solution of methanol (200 ml) and hydrochloric acid (5 ml), stirred for 3 hours, extracted using chloroform, filtered, washed using methanol and hexane, concentrated and filtered, to obtain high-molecular compound having number average molecular weight of 7.1x 103 and weight average molecular weight of 1.3x 104.