TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compounds: The catalyst is tris(dibenzylideneacetone)dipalladium, tetrakis(triphenylphosphine)palladium or bis(triphenylphosphine)palladium dichloride. The usage amount of catalyst is 0.05-20 mol% with respect to compound (III). The solvent is tetrahydrofuran, dimethyl ether, diethyl ether, benzene, or toluene. Preferred Method: Compound (II) is obtained by dissolving 7-bromo-4-(7-bromo-5-iodo-2,1,3-benzoselenadiazol-4-yl)-5-iodo-2,1,3-benzoselenadiazole and an alkyne compound of formula: R1-CC-R2 in solvent (I) in inert gas atmosphere to obtain mixture (I), dripping catalyst (I) and a base in mixture (I), stirring at 130 degrees C for 4 hours, separating, and purifying. The usage amount of catalyst is 10 mol% with respect to 7-bromo-4-(7-bromo-5-iodo-2,1,3-benzoselenadiazol-4-yl)-5-iodo-2,1,3-benzoselenadiazole. The molar ratio of base and alkyne compound is 1:1. The molar ratio of 7-bromo-4-(7-bromo-5-iodo-2,1,3-benzoselenadiazol-4-yl)-5-iodo-2,1,3-benzoselenadiazole and alkyne compound is 1:2. 2-Amino-5-nitroaniline and pyridine are dissolved in thionyl chloride, refluxed at 80-90 degrees C for 24 hours, separated, and purified to obtain 5-nitro-2,1,3-benzothiadiazole. The obtained compound is mixed with hydrobromic acid to obtain mixture (I), which is heat-refluxed to 127 degrees C. Bromine is dripped, and mixture (I) is refluxed for 4 hours and purified to obtain 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole. 4,7-Dibromo-5-nitro-2,1,3-benzothiadiazole and copper powder are added to N,N-dimethylformamide, heated at 120 degrees C for 3 hours, separated, and purified to obtain 4,4'-dibromo-6,6'-dinitro-bi-2,1,3-benzothiadiazole. The obtained compound is added to tetrahydrofuran, tin chloride is added, and the mixture is heat-refluxed at 100 degrees C for 10 hours, separated, and purified to obtain 4,4'-dibromo-6,6'-diiodo-bi-2,1,3-benzothiadiazole. Ethanol is added to the obtained compound to obtain a suspension. The suspension is cooled to 0 degrees C, sodium borohydride is added, and the contents are reacted at room temperature for 20 hours, separated, and purified to obtain 4,4'-dibromo-6,6'-diiodo-bi-bis(1,2-phenylenediamine). The obtained compound is blended with ethanol to obtain mixture (II), which is refluxed, added with aqueous solution of selenium dioxide, refluxed for 2 hours, and filtered to obtain 7-bromo-4-(7-bromo-5-iodo-2,1,3-benzoselenadiazol-4-yl)-5-iodo-2,1,3-benzoselenadiazole. Compound (III) is obtained by dissolving a 4,6-dibromothieno(3,4-b)thiophene derivative of formula (IV) in solvent (II) in inert gas atmosphere to obtain mixture (II), adding sec-n-butyllithium at -78 degrees C, reacting for 1-2 hours, adding tributyltin chloride, reacting at -78 degrees C for 1 hour and at room temperature for 6 hours, and separating the purified product. The molar ratio of compound (IV) E and sec-n-butyllithium is 1:2. The molar ratio of compound (IV) and tributyltin chloride is 1:2.    TECHNOLOGY FOCUS - POLYMERS - Preparation (claimed): In an inert gas atmosphere, a dibromo-benzodi(benzoselenadiazole) derivative of formula (II) and a tributyl(6-(tributylstannyl)thieno(3,4-b)thiophen-4-yl)stannane derivative of formula (III) in a molar ratio of 1.5:1-1:1.5 are dissolved in a solvent. A catalyst is added and Stille coupling reaction is carried out for 6-100 hours at 50-120 degrees C. The reaction product is separated and purified to obtain copolymer (I). Preferred Method: The separation-and-purification process involves adding deionized water and toluene to Stille coupling reaction liquid, decompression-distilling to extract organic phase concentrate, dripping the concentrate in anhydrous ethanol, continuously stirring, separating out precipitated solid, filtering, drying to obtain a solid powder, dissolving the solid powder in chloroform, processing using neutral alumina chromatographic column, removing chloroform under reduced pressure, depositing, filtering, extracting the obtained solid with acetone in Soxhlet extractor, settling, and filtering.