TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): The preparation of (I), comprises (i) dissolving 4,8-bis-(1,3)dithiol-2-ylidene-2,6-bis-trimethylstannanyl-4,8-dihydro-benzo(1,2-b;4,5-b')dithiophene compounds of formula (II) and 5-(4-(2,7-dibromo-9H-carbazol-9-yl)phenyl)thiophene-2-carbaldehyde (III) in a molar ratio of 1:1-1.5:1 in an organic solvent 1, then adding a catalyst, carrying out Stille coupling reaction at 60-120 degrees C 24-72 hours under an inert gas atmosphere, and then separating and purifying to obtain a carbazole-benzodithiophene copolymer of formula (IV), and (ii) adding (IV) and 2-thioxothiazolidin-4-one compounds of formula (V) in a molar ratio of 1:20-1:25 in to an organic solvent 2, then adding 2-3 drops of piperidine, reacting at 65-70 degrees C for 12-14 hours under dark condition, and then separating and purifying to obtain final product. Preferred Method: The separation and purification in the step (i), comprises vacuum distilling the reaction solution of (IV), removing excess organic solvent 1, precipitating with methanol, suction filtering, washing with methanol, and drying, then eluting with chloroform using alumina column chromatography, distilling to remove the organic solvent, precipitating with methanol, filtering, and extracting resulting solid with acetone using Soxhlet extractor for multiple times, again precipitating with methanol, and filtering to obtain (IV). The separation and purification in the step (ii), comprises extracting reaction solution of (I) with dichloromethane, combining organic phases, washing with saturated brine, drying over anhydrous sodium sulfate overnight, filtering, and rotary evaporating to remove the solvent, then dissolving the crude product in chloroform, filtering through a polytetrafluoroethylene membrane, rotary evaporating to remove chloroform, eluting with chloroform using alumina column chromatography, distilling to remove the organic solvent, precipitating with methanol, suction filtering, extracting the resulting solid with acetone using Soxhlet extractor for multiple times, precipitating with methanol, and filtering to obtain (I). Preparation of (II), comprises (a) taking dimethyl 1,3-dithiol-2-ylphosphonate compounds of formula (VII) in dry tetrahydrofuran, cooling to -78 degrees C, adding cyclohexane solution of lithium diisopropylamide slowly and stirring at -78 degrees C for 2-3 hours, then adding tetrahydrofuran solution of benzo(1,2-b;4,5-b')dithiophene-4,8-dione (VI), carrying out Wittig-Horner reaction for 0.5-1 hour under an inert gas atmosphere, then cooling to room temperature, and continuing the reaction for 12-15 hours to obtain 4,8-bis-(1,3)dithiol-2-ylidene-4,8-dihydro-benzo(1,2-b;4,5-b')dithiophene compounds of formula (VIII), where molar ratio between lithium diisopropylamide and (VII) is 1:1-1.5:l, and molar ratio between (VI) and (VII) is 1:2-1:2.5, and (b) taking (VIII) in anhydrous tetrahydrofuran, cooling to -78 degrees C, adding n-hexane solution of n-butyllithium slowly, stirring at -78 degrees C for 2-3 hours under an inert gas atmosphere, adding trimethyltin chloride reagent, and reacting for 0.5-1 hour, then cooling to room temperature, and continuing the reaction for 20-24 hours to obtain (II), where molar ratio between n-butyllithium and (VIII) is 2.2:1-2.5:1, and molar ratio between trimethyltin chloride and (VIII) is 2:1-2.5:1. Preferred Components: The catalyst is organic palladium or mixture of organic palladium and an organic phosphine. The organic palladium is bis(triphenylphosphine)palladium dichloride or tetrakis(triphenylphosphine)palladium, and the mixture of organic palladium and an organic phosphine is mixture of tris(dibenzylideneacetone)dipalladium(0) and tris(2-tolyl)phosphine in a molar ratio of 1:2-1:20. Molar amount of the organic palladium is 0.01-5% of the molar amount of (III). The organic solvent 1 is tetrahydrofuran, N,N-dimethylformamide or toluene, and the organic solvent 2 is chloroform.