TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The inert gas is nitrogen gas or helium gas.    TECHNOLOGY FOCUS - POLYMERS - Preparation (claimed): The selenium-thieno(3,2-b)thiophene-benzothiadiazole copolymer is prepared by mixing 8,15-dibromo-5,18-dithia-4,6,17,19-tetraazapentacyclo(11.7.0.02.10.03.7.016.20)icosa-1(13),2(10),3,6,8,11,14,16,19-nonaene compound of formula (III) and 2,5-dibromoselenopheno(3,2-b)thiophene compound of formula (IV) in molar ratio of 1:1.5-1.5:1, adding solvent (C) and catalyst (C1) and reacting at 50-120 degrees C for 6-108 hours under inert gas atmosphere. The compound (III) is prepared by mixing 7-bromo-4-(7-bromo-5-iodo-2,1,3-benzothiadiazol-4-yl)-5-iodo-2,1,3-benzothiadiazole and acetylene compound of formula: R1-CC-R2, in molar ratio of 1:2, adding catalyst (C2), solvent (A) and base and reacting at 130 degrees C for 4 hours under inert gas atmosphere. The compound (IV) is prepared by mixing tributyl(5-(tributylstannyl)selenopheno(3,2-b)thiophen-2-yl)stannane compound of formula (V) and butyllithium in molar ratio of 1:2, adding solvent (B), mixing for 1-2 hours and reacting at (-78) degrees C for 1 hour under inert gas atmosphere, obtaining reaction mixture and subjecting the obtained reaction mixture to neutral alumina column chromatography.R3,R4=H or 1-20C alkyl;R1,R2=1-20C alkyl;andn=1-100.Preferred Process: The 7-bromo-4-(7-bromo-5-iodo-2,1,3-benzothiadiazol-4-yl)-5-iodo-2,1,3-benzothiadiazole is prepared by mixing 4-nitrobenzene-1,2-diamine and thionyl chloride, adding pyridine, reacting at 85 degrees C, obtaining5-nitro-2,1,3-benzothiadiazole,?adding hydrobromic acid and liquid bromine, mixing, reacting at 127 degrees C for 30 minutes, obtaining 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole, adding copper catalyst and N,N-dimethylformamide solvent, reacting at 120 degrees C for 3 hours, obtaining 7-bromo-4-(7-bromo-6-nitro-2,1,3-benzothiadiazol-4-yl)-5-nitro-2,1,3-benzothiadiazole, adding tin(II) chloride and reacting in presence of tetrahydrofuran solvent at 100 degrees C for 10 hours. Preferred Composition: The base is Bu3N. The molar ratio of base and acetylene compound is 1:1. The catalyst (C1) is palladium(II) acetate. The catalyst (C2) is palladium-tetrakis(triphenylphosphine). The addition amount of catalyst (C1) and catalyst (C2) is 10 mol% and 0.05-20 mol%, respectively. The solvent (A) is dimethylformamide. The solvent (B) is tetrahydrofuran. The solvent (C) is tetrahydrofuran, ethylene glycol dimethyl ether, benzene or toluene. Preferred Definitions:    n=25-75.