TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The catalyst is: tetrakis(triphenylphosphine)palladium or bis(triphenylphosphine)palladium dichloride; or mixture of organopalladium and organophosphine ligand. The organopalladium is tris(dibenzylideneacetone)dipalladium. The organophosphine ligand is tri(o-methylphenyl)phosphine. The molar ratio of organopalladium and organophosphine ligand in the mixture is 1:2-20. The molar ratio of catalyst to (II) is 0.0001-0.05:1. The inert gas used in the inert gas atmosphere is nitrogen gas and/or argon gas.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): The preparation of (I) comprises adding 2,8-dibromo-1,4,9-trithia-trindene compounds of formula (II) and 5,8-bis-(5-trimethylstannanyl-thiophen-2-yl)-2,6,7-trithia-1,3-diaza-trindene compounds of formula (III) in a molar ratio of 1:1.1-1.5 to organic solvent under an inert gas atmosphere, dissolving, adding a catalyst, performing Stille coupling reaction for 24-72 hours at 60-120 degrees C, then separating and purifying to obtain (I) Preferred Method: The separation and purification method comprises distilling off excess solvent under reduced pressure in the reaction solution obtained by the Stille coupling reaction, then dropwisely adding methanol and performing sedimentation, filtering, washing with methanol, drying, eluting through aluminum oxide column chromatography using chloroform, then evaporating to remove the organic solvent, filtering the methanol sedimentation, performing Soxhlet extraction of the resultant solid using acetone, and finally filtering methanol sedimentation to obtain (I). The preparation of (II) comprises: (a) dissolving 2,3-dibromothiophene and alkanoyl chloride in 2-dichloroethane at 0 degrees C ice-salt bath to obtain a mixed solution, slowly dropping dichloromethane solution of aluminum trichloride to the mixed solution, stirring for 2 hours at 0 degrees C, slowly pouring 2 mol/l hydrochloric acid ice to quench the reaction, extracting the obtained reaction solution using diethyl ether, dried over anhydrous magnesium sulfate, and removing organic solvent by rotary evaporation to obtain 2,3-dibromo-5-alkanoyl thiophene, where the molar ratio of 2,3-dibromo-thiophene to alkanoyl chloride is 1:1.1, the molar concentration of 2,3-dibromo-thiophene in the mixed solution is 0.5 mol/l, and the molar concentration of aluminum chloride in the dichloromethane solution of aluminum trichloride is 1.3 mol/l; (b) dissolving the 2,3-dibromo-5-alkanoyl thiophene, 3-thienyl boronic acid and sodium carbonate in a mixed solvent of distilled water, ethanol and toluene under anaerobic conditions, adding tetrakis(triphenylphosphine)palladium(0) catalyst, refluxing and reacting for 20 hours at 90 degrees C, cooling room temperature, followed by quenching reaction using distilled water to obtain a mixture, extracting the mixture with diethyl ether, combining the organic phases, drying the organic phase using anhydrous magnesium sulfate, filtering, removing large number of organic solvent by rotary evaporation, separating and purifying by silica gel column chromatography, eluting the crude product using toluene, and recrystallizing from toluene/methanol to obtain 5-alkanoyl-2,3-bis(3-thienyl)thiophene, where the molar ratio of 2,3-dibromo-5-alkanoyl thiophene, 3-thienyl boronic acid, and sodium carbonate is 1:2.5:10, the volume ratio of distilled water, ethanol and toluene is 1:1:1, the total concentration of dissolved 2,3-dibromo-5-alkanoyl thiophene, 3-thiophene boronic acid and sodium carbonate in the mixed solvent is 10.2 mol/l, and the molar amount of tetrakis(triphenylphosphine)palladium(0) catalyst is 0.02 times the molar amount of 2,3-dibromo-5-alkanoyl thiophene; (c) dissolving the 5-alkanoyl-2,3-bis(3-thienyl)thiophene in dichloromethane under 0 degrees C ice-salt bath, and adding 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and boron trifluoride etherate to obtain a mixed solution, then gradually warming the mixed solution to 30 degrees C and reacting for 12 hours, adding zinc powder and methanol to quench the reaction, continously stirring overnight, filtering reaction mixture, extracting filtrate with dichloromethane, combining organic phases, drying the organic phase using magnesium sulfate, filtering, removing large number of solvent by rotary evaporation, separating by silica gel column chromatography to obtain crude product, eluting crude product using toluene, and recrystallizing from ethanol to obtain 5-alkanoyl-benzo(1,2-b:3,4-b':5,6-d'')trithiophene, where the molar volume ratio of 5-alkanoyl-2,3-bis(3-thienyl)thiophene to dichloromethane is 1 mmol:36 ml, the molar ratio of 5-alkanoyl-2,3-bis(3-thienyl)thiophene, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and boron trifluoride etherate is 5:6:6.5, and the molar ratio of zinc powder and 5-alkanoyl-2,3-bis(3-thienyl)thiophene is 0.01:1; and (d) dissolving the 5-alkanoyl-benzo(1,2-b:3,4-b':5,6-d'')trithiophene and N-bromosuccinimide in N,N-dimethylformamide under anaerobic protection and dark conditions, then warming to 50 degrees C and reacting 12 hours, cooling to room temperature, adding distilled water to the reaction mixture to quench reaction, extracting organic phase with chloroform, washing the organic phase using aqueous saturated sodium thiosulfate, dried over magnesium sulfate, filtering, removing large number of N,N-dimethylformamide solvent by rotary evaporation, separating through silica gel column chromatography to obtain crude product, eluting the crude product using toluene, and recrystallizing from toluene and methanol to obtain (II), where the molar ratio of 5-alkanoyl-benzo(1,2-b:3,4-b':5,6-d'')trithiophene and N-bromosuccinimide is 1:2.5, and the molar volume ratio of 5-alkanoyl-benzo(1,2-b:3,4-b':5,6-d'')trithiophene and N,N-dimethylformamide is 1 mmol:40 ml. The preparation of (III) comprises: (e) dissolving 5,8-dibromo-dithieno(3',2':3,4;2'',3'':5,6)benzo(1,2-c)(1,2,5)thiadiazole and 4-alkyl-(2-trimethyltin)thiophene in molar ratio of 1:1.2 in 40 ml tetrahydrofuran under an inert gas atmosphere, adding tetrakis(triphenylphosphine)palladium(0) catalyst, refluxing and reacting for 48 hours under stirring, cooling to room temperature, removing excess tetrahydrofuran by vacuum distillation, separating though alumina column chromatography, rinsing with chloroform, and removing tetrahydrofuran by evaporation to obtain 5,8-bis(4-alkyl-2-thienyl)dithieno(3',2':3,4;2'',3'':5,6)benzo(1,2-c)(1,2,5)thiadiazole, where the molar amount of tetrakis(triphenylphosphine)palladium(0) is 0.025 times the molar amount of 5,8-dibromo-dithieno(3',2':3,4;2'',3'':5,6)benzo(1,2-c)(1,2,5)thiadiazole; and (f) dissolving the 5,8-bis(4-alkyl-2-thienyl)dithieno(3',2':3,4;2'',3'':5,6)benzo(1,2-c)(1,2,5)thiadiazole in tetrahydrofuran under an inert gas atmosphere, cooling to -78 degrees C, slowly adding n-hexane solution of n-butyl lithium, reacting for 2 hours at -78 degrees C under stirring, adding trimethyltin chloride, heat preserving for 0.5 hours, returning to room temperature, reacting continously for 24 hours, and removing excess solvent and trimethyltin chloride by vacuum distillation to obtain (III), where the molar volume ratio 5,8-bis(4-alkyl-2-thienyl)dithieno(3',2':3,4;2'',3'':5,6)benzo(1,2-c)(1,2,5)thiadiazole and tetrahydrofuran is 1 mmol:30 ml, the molar concentration of n-butyl lithium in n-hexane solution is 2.5 mol/l, the molar amount of n-butyl lithium is 2.5 times the molar amount of the 5,8-bis(4-alkyl-2-thienyl)dithieno(3',2':3,4;2'',3'':5,6)benzo(1,2-c)(1,2,5)thiadiazole, and the molar amount of trimethyltin chloride is 2.5 times the molar amount of the 5,8-bis(4-alkyl-2-thienyl)dithieno(3',2':3,4;2'',3'':5,6)benzo(1,2-c)(1,2,5)thiadiazole. Preferred Components: The organic solvent is tetrahydrofuran, N,N-dimethylformamide or toluene.