NOVELTY - A dibenzothiophene compound chosen from compound (I)-(V), is new.    USE - New dibenzothiophene compound is used for preparing polymer for organic electroluminescent device, organic solar cell and organic field-effect transistor (all claimed).    ADVANTAGE - The dibenzothiophene compound has excellent solubility in organic solvent. The polymer prepared using the dibenzothiophene compound has improved electron transport property.    DETAILED DESCRIPTION - A dibenzothiophene compound chosen from compounds of formulae (I)-(V), is new.    X=Br or I;and    R1=1-30C alkyl.    INDEPENDENT CLAIMS are included for the following: (i) preparation of dibenzothiophene compounds (I)-(V). Bis(S,S-dioxide-dibenzothiophene) and cyclopentadiene, or bis(S,S-dioxide-dibenzothiophene) and pyrrole are dissolved in organic solvent, respectively, reacted under acidic conditions for 1-10 hours, extracted, dried and purified, to obtain bromo-2,10-bis(S,S-dioxo-dibenzothiophene)cyclopentadiene or bromo-5,7-bis(S,S-dioxo-dibenzothiophene)pyrrole. 2,4-Dibromo-1-methylthiophenyl in acetic acid is mixed with hydrogen peroxide, placed in ice bath, reacted for 4-10 hours, extracted, dried, resultant product is dissolved in organic solvent, palladium catalyst is added, reacted for 40-100 degrees C for 8-25 hours, extracted, dried, purified, phosphorus pentoxide is added, reacted for 2-30 hours, filtered, dried, pyridine is added, refluxed for 2-30 hours, dried, purified, resultant product is dissolved in organic solvent, oxidizing agent is added, reacted for 2-10 hours, extracted, dried and purified, to obtain 3,9-bisbrominated-(S,S-dioxo-dibenzothiophene)cyclopentadiene. 3,6-Dimethylthio-2,7-dibromo-alkyl-substituted carbazole is dissolved in trifluoroacetic acid, hydrogen peroxide is added, placed in ice bath, reacted for 2-15 hours, extracted, dried, purified, dissolved in trifluoromethanesulfonic acid, phosphorus pentoxide is added, reacted for 2-20 hours, filtered, dried, residue is added to pyridine, refluxed for 2-30 hours, dried, purified, resultant product is dissolved in organic solvent, oxidizing agent is added, reacted for 2-10 hours, extracted, dried and purified, to obtain 3,9-bis-brominated-bis(S,S-dioxo-dibenzothiophene)pyrrole. 3,6-Dimethylsulfinyl-2,7-dibromo-alkyl-substituted carbazole is mixed with 4-bromophenyl or 3-bromophenyl boronic acid in molar ratio of 1:2-10, organic solvent and palladium catalyst are added, reacted at 50-100 degrees C for 8-20 hours, extracted, dried, purified, phosphorus pentoxide is added, reacted for 2-20 hours, filtered, dried, residue is added to pyridine, refluxed for 2-30 hours, dried, purified, resultant product is dissolved in organic solvent, oxidizing agent is added, reacted for 2-10 hours, extracted, dried and purified, to obtain 2,10-bis-bromo(S,S-dioxo-dibenzothienyl)pyrrole; and # (ii)polymer, which comprises structural unit (VI) derived from dibenzothiophene compound.    x=0-1;    x+y=1;    n=1-300;    group A=group of formula (i) or (ii);    Ar'=group chosen from 28 groups e.g. groups of formulae (iii)-(vii);and    Z1,Z2=H or F.