TECHNOLOGY FOCUS - POLYMERS - Preparation: Preparing conjugated polymer with main chain containing thieno(3,2-b)thiophene ethylene involves: (a) dissolving 1 mol of 3-hexyl-thieno(3,2-b)thiophene into N,N'-dimethyl formamide solvent; adding N-bromosuccimide into it; the mol ratio of N-bromosuccimide to 3-hexyl-thieno(3,2-b)thiophene is 2-2.5; reacting for 6-24 hours at room temperature; washing by water and extracting; spinning to remove solvent; separating by chromatography to obtain 2,5-dibromo-3-hexyl-thieno(3,2-b)thiophene; or, dissolving 1 mol of 3,4-dihexyl-thieno(3,2-b)thiophene into N,N'-dimethyl formamide solvent; adding N-bromosuccimide into it; the mol ratio of N-bromosuccimide to 3-hexyl-thieno(3,2-b)thiophene is 2-2.5; reacting for 6-24 hours at room temperature; washing by water and extracting; spinning to remove solvent; separating by chromatography to obtain 2,5-dibromo-3,4-hexyl-thieno(3,2-b)thiophene; and (b) dissolving 2,5-dibromo-3-hexyl-thieno(3,2-b)thiophene into toluene from (a); adding 1,2(E)-(bistributyltin)ethylene; the mol ratio of 2,5-dibromo-3-hexyl-thieno(3,2-b)thiophene to 1,2(E)-(bistributyltin)ethylene is 1; inputting inert gas for 10-20 minutes; adding palladium catalyst with the catalytic amount; continuously inputting inert gas for 20-30 minutes; under the protection of inert gas, reacting for 12-24 hours at 80-120 degrees C; adding methanol to settle; filtering to obtain precipitate; washing methanol and hexane from the Soxlet extracting device; dissolving solid residue in the Soxlet extracting device; reducing pressure to remove chloroform to obtain polymer with the formula (1); or dissolving2,5-dibromo-3,4-hexyl-thieno(3,2-b)thiophene from (a) into toluene; adding 1,2(E)-(bistributyltin)ethylene; the mol ratio of 2,5-dibromo-3-hexyl-thieno(3,2-b)thiophene to 1,2(E)-(bistributyltin)ethylene is 1; inputting inert gas for 10-20 minutes; adding palladium catalyst with the catalytic amount; continuously inputting inert gas for 20-30 minutes; under the protection of inert gas, reacting for 12-24 hours at 80-120 degrees C; adding methanol to settle; filtering to obtain precipitate; washing methanol and hexane from the Soxlet extracting device; dissolving solid residue in the Soxlet extracting device; reducing pressure to remove chloroform to obtain polymer with the formula (2). Preferred Method: The 3-hexyl-thieno(3,2-b)thiophene is prepared by: (a) dissolving 1 mol of 3-bromothiophene into methylene dichloride; adding anhydrous aluminum trichloride; the mol ratio of methylene dichloride to aluminum trichloride is 1-2.2; blending to react for 0.5-1 hour; dripping heptanoyl chloride; the mol ratio of 3-bromothiophene to heptanoyl chloride is 1-1.2; blending continuously to react for 4-6 hours; washing by water and extracting; spinning to remove solvent to obtain 3-bromo-2-thienylheptanone; (b) dissolving 1 mol of 3-bromo-2-thienylheptanone from (a) into N,N'-dimethylformamide solvent; adding potassium carbonate; the mol ratio of potassium carbonate to 3-bromo-2-thienylheptanone is 2-2.2; blending to react for 0.5-1 hour; adding mercaptoethyl acetate; the mol ratio of mercaptoethyl acetate to 3-bromo-2-thienylheptanone is 1-1.2; blending to react for 24-36 hours; washing by water and extracting; spinning to remove solvent to obtain 3-hexyl-2-thieno(3,2-b)thienyl ethyl formate; (c) dissolving 3-hexyl-2-thieno(3,2-b)thienyl ethyl formate from (b) into mixed solvent of tetrahydrofuran and methanol; adding lithium hydroxide aqueous solution; the mol ratio of lithium hydroxide aqueous solution to 3-hexyl-2-thieno(3,2-b)thienyl ethyl formate is 1-1.2; reacting for 4-6 hours at 60-80 degrees C; spinning to remove solvent; adding hydrochloric acid into residue to separate solid; filtering and washing by water; drying in vacuum to obtain 3-hexyl-2-thieno(3,2-b)thienyl formic acid; and (d) dissolving 1 mol of 3-hexyl-2-thieno(3,2-b)thienyl formic acid from (c) into quinone solvent and adding copper powder; the mol ratio of copper powder to 3-hexyl-2-thieno(3,2-b)thienyl formic acid is 1-2; reacting for 3-6 hours at 230-260 degrees C; cooling to room temperature; adding hexane; separating organic phase; washing by hydrochloric acid; spinning to remove solvent; column chromatographing to obtain 3-hexyl-thieno(3,2-b)thiophene. The 3,4-dihexyl-thieno(3,2-b)thiophene is prepared by: (a) dissolving 1 mol of 3-bromo-4-hexyl-thiophene into methylene dichloride; adding anhydrous aluminum trichloride; the mol ratio of methylene dichloride to aluminum trichloride is 1-2.2; blending to react for 0.5-1 hour; dripping heptanoyl chloride; the mol ratio of 3-bromothiophene to heptanoyl chloride is 1-1.2; blending continuously to react for 4-6 hours; washing by water and extracting; spinning to remove solvent to obtain 3-bromo-4-hexyl-2-thienylheptanone; (b) dissolving 1 mol of 3-bromo-4-hexyl-2-thienylheptanone from (a) into N,N'-dimethylformamide solvent; adding potassium carbonate; the mol ratio of potassium carbonate to 3-bromo-4-hexyl-2-thienylheptanone is 2-2.2; blending to react for 0.5-1 hour; adding mercaptoethyl acetate; the mol ratio of mercaptoethyl acetate to 3-bromo-4-hexyl-2-thienylheptanone is 1-1.2; blending to react for 24-36 hours; washing by water and extracting; spinning to remove solvent to obtain 3,4-dihexyl-2-thieno(3,2-b)thienyl ethyl formate; (c) dissolving 3,4-dihexyl-2-thieno(3,2-b)thienyl ethyl formate from (b) into mixed solvent of tetrahydrofuran and methanol; adding lithium hydroxide aqueous solution; the mol ratio of lithium hydroxide aqueous solution to 3,4-dihexyl-2- thieno(3,2-b)thienyl ethyl formate is 1-1.2; reacting for 4-6 hours at 60-80 degrees C; spinning to remove solvent; adding hydrochloric acid into residue to separate solid; filtering and washing by water; drying in vacuum to obtain 3,4-dihexyl-2-thieno(3,2-b)thienyl formic acid; and (d) dissolving 1 mol of 3,4-dihexyl-2-thieno(3,2-b)thienyl formic acid from (c) into quinone solvent and adding copper powder; the mol ratio of copper powder to 3,4-dihexyl-2-thieno(3,2-b)thienyl formic acid is 1-2; reacting for 3-6 hours at 230-260 degrees C; cooling to room temperature; adding hexane; separating organic phase; washing by hydrochloric acid; spinning to remove solvent; column chromatographing to obtain 3,4-dihexyl-thieno(3,2-b)thiophene.