TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (claimed): The compound (I) is prepared by subjecting benzothiadiazole derivative of formula (A) and dithiophene derivative of formula (B) at molar ratio of 1: 1.5-1.5:1 to Stille coupling reaction in organic solvent in the presence of organic palladium catalyst under anaerobic atmosphere, separating, and purifying. Preferred Components: The organic palladium catalyst is tris(dibenzylideneacetone)dipalladium, tetrakis(triphenylphosphine)palladium, or bis(triphenylphosphine)palladium dichloride. Preferred Method: The Stille coupling reaction is carried out at 50-120 degrees C for 6-100 hours. The separation and purification is carried out by adding mixed toluene and deionized water to reaction product, extracting to obtain organic phase, adding ethanol to carry out precipitation, filtering, evaporating organic solvent to dryness to obtain solid, dissolving in chloroform, adding to neutral alumina chromatography column, removing organic solvent, precipitating with methanol, filtering to obtain solid, extracting with acetone, recovering acetone solution, precipitating with methanol, and filtering. The compound (A) is prepared by subjecting benzothiadiazole compound of formula (C) with acetylene derivative of formula (E) to coupling reaction in organic base-containing solvent in the presence of catalyst, separating by adding water and methylene chloride, extracting to obtain organic layer, drying with anhydrous sodium sulfate, filtering, and purifying through silica gel column chromatography. The organic base is triethylamine. The catalyst is palladium acetate. The compound (B) is prepared by reacting bromine-containing dithiophene derivative of formula (D) with tetrahydrofuran at anaerobic environment, adding n-butyllithium at molar ratio of 1:2 at - 78 degrees C, stirring for 1-2 hours, reacting with tributyltin chloride at molar ratio of 1:2 at - 78 degrees C for 1 hour, cooling to room temperature, stirring for 6 hours, adding saturated sodium chloride aqueous solution to stop reaction, extracting with anhydrous diethyl ether to obtain organic phase, vacuum-drying, and removing solvent.