TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The organic palladium catalyst is tris(dibenzylideneacetone)dipalladium, tri-o-tolylphosphine of bis (triphenylphosphine)palladium dichloride or tetrakis(triphenylphosphine)palladium. The molar ratio of organic palladium catalyst and compound B is 1:10000-1:20.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The coupling reaction is carried out for 21-72 hours. The separating and purifying steps comprise performing coupling reaction of compound A and compound B with methanol to precipitate, filtering the precipitate, purifying by chromatography, filtering and drying obtained solid, and again precipitating with methanol. The compound (A) is prepared by adding thiophen-2-yl-acetic acid compound of formula (C), 1,3-dicyclohexylcarbodiimide carbodiimide and 4-dimethylaminopyridine with dichloromethane solution in a mole ratio of 3:3:1-4:3.5:1 under the protection of nitrogen at room temperature for 12-15 hours to obtain 1,3-di-thiophen-2-yl-propan-2-one compound of formula (D), purifying the reaction liquid, reacting (D) and benzo(1,2-b;4,3-b')dithiophene-4,5-dione compound of formula(E) with solvent including ethanol and propanol in a mole ratio of 1:1.5:1 to obtain 1,6-dithia-trinden-8-one compound of formula (F), dripping the mixed liquid in potassium hydroxide, sodium hydroxide or alcohol saturated solution, continuing reaction for 10-15 minutes, reacting (F) with n-butyl lithium normal hexane solution and tetrahydrofuran solution in a mole ratio of 1:2.2-1:2.5 under the protection of nitrogen at -78 degrees C, for 2-2.5 hours, raising the temperature to room temperature, mixing (F) and trimethyl tin chloride in a mole ratio of 1:2-1:2.5, then continuously reacting for 20-24 hours and purifying. The compound (E) is prepared by adding (3,3')bithiophenyl compound of formula (G) with oxalyl chloride and 1,2-dichloroethane solution in a mole ratio of 1:1.5-1:1.8 and temperature of 3 degrees C for 5 days and 3 times, reacting the liquid for 10-15 days under protection of argon gas to obtain reaction mix liquid, and freezing the reaction mix liquid.