TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (claimed): 4,7-Dibromo-benzo(1,2,5)thiadiazole is reacted with alkylthiophene to obtain dithiophene-substituted compound of formula (9a). The compound (9a) is reacted with N-bromo succinimide in organic solvent to obtain bromo-substituted compound of formula (4a). The compound (4a) is coupled with (9,9-dimethyl-9H-fluoren-2-yl)-(9,9 -dimethyl-9H-fluoren-3-yl)-(4-(4,4,5,5-tetramethyl-(1,3,2)dioxaborolan-2-yl)-phenyl)-amine to obtain dithiophene-substituted fluorenyl-containing compound of formula (6a). The compound (6a) is subjected to Vilsmeier-Haack reaction to obtain an aldehyde-substituted compound of formula (7a). The compound (7a) is reacted with cyanoacetic acid in chloroform in presence of piperidine to obtain the dye of formula (1a).R=H or hexyl. Preferred Definitions:    R 2-R 5=H or 4-10C alkyl;    Ar=group of formula (a);and    n=1.    SPECIFIC COMPOUNDS - (2Z)-3-(5-(7-(5-(4-(Bis(9,9-dimethyl-9H-fluoren-2-yl)amino)phenyl)thiophen-2-yl)-2,1,3-benzothiadiazol-4-yl)thiophen-2-yl)-2-cyanoprop-2-enoic acid of formula (A) and (2Z)-3-(5-(7-(5-(4-(bis(9,9-dimethyl-9H-fluoren-2-yl)amino)phenyl)-3-pentylthiophen-2-yl)-2,1,3-benzothiadiazol-4-yl)-4-pentylthiophen-2-yl)-2-cyanoprop-2-enoic acid are specifically claimed as the organic dye.    EXAMPLE - (In g) 4,7-dibromo-1,2,3-benzothiadiazole (2) and tributyl(2-thienyl)stannane (5.2 ml) were reacted in presence of palladium catalyst to obtain 4,7-dithiophen-2-yl-benzo(1,2,5)-thiadiazole. The obtained compound (350 mg) was reacted with N-bromosuccinimide in acetic acid to obtain 4-(5-bromothiophen-2-yl)-7-(thiophen-2-yl)benzo(1,2,5)thiadiazole. The bromo compound (170 mg) was reacted with (9,9-dimethyl-9H-fluoren-2-yl)-(9,9 -dimethyl-9H-fluoren-3-yl)-(4-(4,4,5,5-tetramethyl-(1,3,2)dioxaborolan-2-yl)-phenyl)-amine (272 mg) in presence of toluene (20 ml) and mixture of ethanol and water. The organic layer was separated from the reaction mixture to obtain bis(9,9-dimethyl-9H-fluoren-2-yl)-(4-(5-(7-thiophen-2-yl benzo(1,2,5)thiadiazol-4-yl)-thiophen-2-yl)-phenyl)amine. The amine compound in dimethylformamide was reacted with phosphorus oxychloride to obtain an aldehyde. The aldehyde compound was reacted with cyanoacetic acid (10 mg) to obtain (2Z)-3-(5-(7-(5-(4-(bis(9,9-dimethyl-9H-fluoren-2-yl)amino)phenyl)thiophen-2-yl)-2,1,3-benzothiadiazol-4-yl)thiophen-2-yl)-2-cyanoprop-2-enoic acid having melting point of 290 degrees C with yield of 58%.