Color tuning in benzo[1,2,5]thiadiazole-based small molecules by amino conjugation/deconjugation: Bright red-light-emitting diodes

Bipolar compounds (referred to in general as btza) containing a benzo[1,2,5]thiadiazole core and peripheral diarylamines and/ or 4-tert-butylphenyl moieties have been synthesized via palladium-catalyzed cross-coupling reactions of 4,7-dibromobenzo[1,2,5]thiadiazole with appropriate stannyl compounds. These compounds are fluorescent and the emission color ranges from green to red. The fluorescence of the compounds originates from a charge-transfer process and exhibits solvatochromism. These red-light-emitting materials are amorphous and devices of different configurations were fabricated: 1) ITO/btza/TPBI/ Mg:Ag; II) ITO/btza/Alq(3)/Mg:Ag; III) ITO/btza/Mg:Ag (where ITO indium tin oxide, TPBI = 1,3,5-tris(N-phenylbezimidazol-2-yl)benzene, and Alq(3) = tris(8-hydroxyquinoline)aluminum). The performance of some of the red-light-emitting devices appears to be very promising.