TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): The preparation of (I), comprises (i) (1) adding 3,7-dibromo-N-alkylphenothiazine and a divalent palladium catalyst into a reaction kettle, adding cuprous iodide under nitrogen atmosphere, then adding toluene, triethylamine and 3,3-dimethyl-3-hydroxy-propyne, reacting by heating, filtering the resultant reaction product, washing with anhydrous diethyl ether, removing the solvent by distillation at atmospheric pressure, and purifying by column chromatography to obtain an intermediate, then refluxing the intermediate and sodium hydroxide with toluene solvent under nitrogen atmosphere, distilling off the toluene solvent under reduced pressure, and purifying by column chromatography to obtain N-alkyl-3,7-bis(ethynyl)phenothiazine monomer, and (ii) adding N-alkyl-3,7-bis(ethynyl)phenothiazine monomer and N-octyl-3,6-bis(ethynyl)carbazole monomer or 4,7-di(ethynyl)-2,1,3-benzothiadiazole monomer into o-dichlorobenzene, and stirring until completely dissolved to obtain a mixed solution, transferring the resulting mixed solution to a catalyst system containing cuprous chloride and tetramethylethylenediamine, reacting in presence of air, then pouring the reaction solution into a mixed solution of methanol and concentrated hydrochloric acid for precipitation, filtering, and vacuum drying the resulting solid to obtain final product. Preferred Components: In 3,6-dibromo-N-alkylphenothiazine, alkyl is 1-18C alkyl. Molar ratio between 3,7-dibromo-N-alkylphenothiazine and divalent palladium catalyst is 1:0.02-0.05, and molar ratio between 3,7-dibromo-N-alkylphenothiazine and cuprous iodide is 1:0.001-0.005. Based on per mmol of 3,7-dibromo-N-alkylphenothiazine, the used amount of toluene is 6-15 ml, amount of triethylamine is 6-15 ml, and amount of 3,3-dimethyl-3-hydroxy-propyne is 0.3-1.5 ml. In the step (ii), molar ratio between N-alkyl-3,7-bis(ethynyl)phenothiazine monomer and N-octyl-3,6-bis(ethynyl)carbazole monomer or 4,7-di(ethynyl)-2,1,3-benzothiadiazole monomer is 1:1-3. The step (ii): based on per mmol of diacetylene monomer, the used amount of cuprous chloride is 20-30 mg/, amount of tetramethylethylenediamine is 0.06-0.08 ml, and amount of o-dichlorobenzene is 20-50 ml; in the mixed solution of methanol and concentrated hydrochloric acid, the amounts of methanol and concentrated hydrochloric acid are 50-100 ml and 0.1-0.3 ml per mmol of diacetylene monomer respectively; the diacetylene monomer is mixture of N-alkyl-3,7-bis(ethynyl)phenothiazine monomer and N-octyl-3,6-bis(ethynyl)carbazole monomer or 4,7-di(ethynyl)-2,1,3-benzothiadiazole monomer. Preferred Method: The step (i): the reaction temperature is 80-120 degrees C, and the reaction time is 10-24 hours; molar ratio between the intermediate and sodium hydroxide is 1:1-2; the refluxing temperature is 80-120 degrees C, and the refluxing time is 3-10 hours. The step (ii): the dissolution temperature is 20-60 degrees C; and the stirring time is for 4-60 minutes.