TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (claimed): The preparation of (I) comprises synthesizing with 2,2',5',2'-tetrathiophenyl-5-formaldehyde, dichloromethane, N,N-methyl acid amide and phosphorus oxychloride at ratio of 25:6:7. Preferred Component: The composition comprises meso-5,10,15,20-tetra(2,2',5',2''-trithiophenyl), electron donor (D), porphyrin used as light absorbent and electron acceptor (A). The volume ratio of dichloromethane to n-hexane is 2:3. Preferred Processes: The method comprises evaporating 2,2',5',2'-tetrathiopheyla-5-formaldehyde solvent to obtain yellow solid, adding sodium hydroxide solution into yellow solid substance and stirring, adjusting pH to 6-9, stirring under magnetic force, water boiling, filtering, water washing and drying in vacuum box, to obtain yellow solid, recrystallizing and purifying. The preparation comprises after purifying to compound 2,2',5',2'-tetrathiophena-5-formaldehyde and pyrrole evaporation at mol ratio of 1:0.5:1.5, refluxing at 30-60 degrees C, and reacting. The method comprises preparing N,N-dimethyl formamide, phosphorus oxychloride, dichloromethane, N,N-dimethyl formamide and phosphorus oxychloride, adding dichloromethane into container A and magnetic stirring, adding into ice bath, reducing temperature of - 20 to 10 degrees C, adding N,N-dimethyl formamide to form mixed solution, when mixed solution is - 20 to 10 degrees C, dropping phosphorus oxychloride, continuously magnetically stirring at 30-50 degrees C of warm water to form clear light yellow solution until solution container, at mol ratio of 20-25:1 of dichloromethane and trithiophene, magnetically stirring container into mixture ice bath, magnetically stirring to completely dissolve to form mixing solution with dichloromethane; and in container, mixing liquid at - 20 to 10 degrees C, reacting obtained light yellow solution into second container, and standing 8 hours at 15 degrees C to obtain solution. The purification comprises using methylene dichloride and n-hexane to obtain yellow solid, dissolving yellow solid to obtain mixed solution A with methylene dichloride under magnetic stirring, heating mixed solution A under reflux state into n-hexane, continuously heating and refluxing for 20-40 minutes, naturally cooling to room temperature after adding mixed solution into ice bath for 3-4 hours to obtain yellow solid crystal, filtering to obtain yellow solid, filtering, recrystallizing obtained yellow crystal in oven at 60 degrees C for 4-6 hours to obtain purified 2,2',5',2'-tetrathiophena-5-formaldehyde. The sodium hydroxide solution is used to adjust pH to 8-9.