TECHNOLOGY FOCUS - POLYMERS - Preparation (claimed): The dithiophene-benzodiazepine copolymer is prepared by dissolving tetrahydrophenanthrene derivative of formula (II) and thieno(3,2-b)thiophene derivative of formula (III) in molar ratio of 1.5:1-1:1.5 in solvent, adding catalyst, performing Stille coupling reaction at 50-120 degrees C for 6-100 hours under inert gas atmosphere, obtaining reaction mixture, separating and purifying. Preferred Processes: The preparation of dithiophene-benzodiazepine copolymer further involves extracting reaction solution obtained by the Stille coupling reaction with deionized water and toluene, distilling the resultant organic phase under reduced pressure, obtaining concentrate, adding anhydrous ethanol, stirring uniformly, precipitating, filtering, drying, obtaining solid powder, dissolving the obtained solid powder in chloroform, subjecting the resultant solution to column chromatography, decompressing, removing chloroform under reduced pressure, precipitating using methanol, filtering, extracting the resultant solid using a Soxhlet extractor with acetone and methanol, sedimenting, performing suction filtration process and obtaining purified (3,2-b)dithiophene-benzodiazepine copolymer. The compound (II) is prepared by dissolving 7-bromo-4-(7-bromo-5-iodo-2,1,3-benzoselenadiazol-4-yl)-5-iodo-2,1,3-benzoselenadiazole and acetylene group-containing compound of formula: R1-CC-R2 in solvent, obtaining mixed solution, adding catalyst and alkali, reacting, obtaining reaction mixture at 130 degrees C for 4 hours, separating and purifying. The addition amount of the 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 bromo-4-(7-bromo-5-iodo-2,1,3-benzoselenadiazol-4-yl)-5-iodo-2,1,3-benzoselenadiazole is prepared by dissolving 2-amino-5-nitroaniline and pyridine in thionyl chloride, reacting at 80-90 degrees C for 24 hours, separating the resultant reaction mixture, purifying, obtaining 5-nitro-2,1,3-benzothiadiazole, adding hydrobromic acid, mixing uniformly, refluxing at 127 degrees C, adding liquid bromine, refluxing for 4 hours, adding copper powder and N,N-dimethylformamide, reacting at 120 degrees C for 3 hours, obtaining reaction mixture, separating the obtained reaction mixture, purifying, adding tin chloride, mixing uniformly, reacting at 100 degrees C for 10 hours, separating, purifying, adding ethanol to the resultant mixture, cooling at 0 degrees C, adding sodium borohydride, reacting at room temperature for 20 hours, separating, purifying, mixing the resultant mixture with ethanol, refluxing, adding aqueous solution of selenium dioxide, reacting for 2 hours and filtering the resultant reaction mixture. The compound (III) is prepared by dissolving 2,5-dibromothieno(3,2-b)thiophene derivative of formula (IV) in solvent, adding n-butyllithium, reacting at (-78) degrees C for 1-2 hours, adding tributyltin chloride, reacting at (-78) degrees C for 1 hour and then at room temperature for 6 hours, separating the resultant reaction mixture and purifying. Preferred Composition: The catalyst is tris(dibenzylideneacetone) dipalladium, tetrakis(triphenylphosphine)palladium or bis(triphenylphosphine)palladium dichloride. The solvent is tetrahydrofuran, ethylene glycol dimethyl ether, diethyl ether, benzene or toluene. The usage amount of catalyst is 0.05-20 mol%. The molar ratio of 2,5-dibromothieno(3,2-b)thiophene derivative and n-butyllithium is 1:2. The molar ratio of 2,5-dibromothieno(3,2-b)thiophene derivative and tributyltin chloride is 1:2. The molar ratio of alkali and acetylene group-containing compound is 1:1. The molar ratio of bromo-4-(7-bromo-5-iodo-2,1,3-benzoselenadiazol-4-yl)-5-iodo-2,1,3-benzoselenadiazole and acetylene group-containing compound is 1:2.