TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (claimed): 8,15-Dibromo-11,12-diiodo-5,18-dithia-4,6,17,19-tetraazapentacyclo(11.7.0.0 2,10.0 3,7.0 16,20)icosa-1(13),2(10),3,6,8,11,14,16,19-nonaene is reacted with alkyne compound of formula (II) in molar ratio of 1:2 under inert atmosphere in presence of primary solvent and primary catalyst under alkaline solution at 100-150 degrees C for 2-6 hours, to obtain 8,15-dibromo-5,18-dithia-4,6,17,19-tetraazapentacyclo(11.7.0.0 2,10.0 3,7.0 16,20)icosa-1(13),2(10),3,6,8,11,14,16,19-nonaene of formula (III). A 5,11-dibromo-8-silatricyclo(7.4.0.0 2,7)trideca-1(9),2(7),3,5,10,12-hexaene of formula (IV) is dissolved in solvent of tetrahydrofuran under inert atmosphere, n-butyl lithium is added at -78 degrees C, stirred for 1-2 hours, tributyltin chloride is added, reacted for 1 hour, and heated at room temperature for 6 hours, to obtain 5,11-bis(tributylstannyl)-8-silatricyclo(7.4.0.0 2,7)trideca-1(9),2(7),3,5,10,12-hexaene derivative of formula (V). 8,15-Dibromo-5,18-dithia-4,6,17,19-tetraazapentacyclo(11.7.0.0 2,10.0 3,7.0 16,20)icosa-1(13),2(10),3,6,8,11,14,16,19-nonaene (III) and 5,11-bis(tributylstannyl)-8-silatricyclo(7.4.0.0 2,7)trideca-1(9),2(7),3,5,10,12-hexaene derivative (V) are subjected to coupling reaction in molar ratio of 1:1.5-1.5:1, under inert atmosphere in presence of secondary solvent and secondary catalyst at 50-120 of 6 to 100 hours, to obtain silicon-containing fluorene-benzodiazepin (benzothiadiazole) copolymer (I). The molar amount of 5,11-dibromo-8-silatricyclo(7.4.0.0 2,7)trideca-1(9),2(7),3,5,10,12-hexaene (IV) and n-butyl lithium is 1:2. The molar ratio of tributyltin chloride is same as n-butyl lithium. Preferred Process: The 8,15-dibromo-5,18-dithia-4,6,17,19-tetraazapentacyclo(11.7.0.0 2,10.0 3,7.0 16,20)icosa-1(13),2(10),3,6,8,11,14,16,19-nonaene (III) is prepared by adding thionyl chloride into 4-nitrobenzene-1,2-diamine, stirring under reflux at 85 degrees C, adding pyridine dropwise, obtaining 5-nitro-2,1,3-benzothiadiazole, adding hydrobromic acid, stirring at 127 degrees C under reflux for 30 minutes, forming 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole by dropping liquid bromine, adding resulted product into N,N-dimethylformamide solvent in presence of copper compound catalyst, reacting by heating at 120 degrees C for 3 hours, forming 7-bromo-4-(7-bromo-5-nitro-2,1,3-benzothiadiazol-4-yl)-5-nitro-2,1,3-benzothiadiazole, reacting with tin(II) chloride in presence of tetrahydrofuran solvent by heating at 100 degrees C under reflux for 10 hours, and obtaining product. Preferred Composition: The primary catalyst is palladium acetate. The amount of primary catalyst 10 mol% with respect to the amount of 8,15-dibromo-5,18-dithia-4,6,17,19-tetraazapentacyclo(11.7.0.0 2,10.0 3,7.0 16,20)icosa-1(13),2(10),3,6,8,11,14,16,19-nonaene. The alkaline solution comprises tributylamine solution. The molar ratio of alkaline solution containing tributylamine and alkyne compound (II) is 1:1. The primary solvent is N,N-dimethylformamide. The secondary catalyst is tetrakis(triphenylphosphine)palladium, tris(dibenzylidene acetone)palladium or bis(triphenylphosphine)palladium dichloride. The amount of secondary catalyst is 0.05-20 mol% with respect to the amount of 5,11-bis(tributylstannyl)-8-silatricyclo(7.4.0.0 2,7)trideca-1(9),2(7),3,5,10,12-hexaene derivative. The secondary solvent is tetrahydrofuran, ethylene glycol dimethyl ether, ether, benzene or toluene. Preferred Definitions:    n=35-54.