TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (claimed): Compound (I) is prepared by performing Suzuki coupling reaction of compound (II) and compound (III) at mol ratio of 1:1.5-1.5:1 at 50-120 degrees C for 6-100 hours in the presence of catalyst, solvent and sodium carbonate under inert gas atmosphere, and separating and purifying. Compound (II) is prepared by taking 4,4'-dibromo-6,6'-diiodo-2,1,3-benzothiadiazole of formula (i) and chlorine-containing silicon compound of formula (ii) at mol ratio of 1:2, dissolving compound (i) in N,N-dimethylformamide under inert gas atmosphere, slowly dropping n-butyllithium at mol ratio of 1:2-1:4, reacting while stirring for 2 hours, slowly injecting compound (ii) at - 90 degrees C, heating to room temperature, reacting for 10 hours, washing with water, extracting with ethanol, taking organic phase, drying using anhydrous sodium sulfate, filtering, vacuum-distilling and separating in silica gel chromatographic column. Compound (III) is prepared by dissolving dibromo-carbazole derivative of formula (iii) in tetrahydrofuran under inert gas atmosphere, slowly adding n-butyllithium at mol ratio of 1:2, cooling to - 78 degrees C, reacting while stirring for 1.5-2 hours, adding 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane at mol ratio of 2:1, reacting for 1 hour, heating to room temperature, reacting while stirring for 6 hours, adding saturated sodium chloride aqueous solution, stopping reacting, extracting with ethanol, drying using anhydrous sodium sulfate, rotationally evaporating solvent and separating in silica gel chromatographic column.Preferred Components: The catalyst having adding amount of 0.5-20 mol is tris(dibenzylideneacetone)dipalladium, bis(triphenylphosphine)palladium dichloride and tetrakis(triphenyl phosphine) palladium. The organic solvent is tetrahydrofuran, dimethyl ether, diethyl ether, benzene or toluene.Preferred Method: Separating and purifying comprises extracting toluene and deionized water to reaction system, taking organic phase, vacuum-distilling, dropping into anhydrous ethanol, precipitating, filtering, drying to obtain solid powder, dissolving in chloroform, separating in silica gel chromatographic column, removing organic solvent, settling, performing Soxhlet extraction with acetone for 3 days, settling and vacuum-filtering.