Light-Emitting Carbazole Derivatives:  Potential Electroluminescent Materials

• Published in: Journal of the American Chemical Society Vol. 123; no. 38; pp. 9404 - 9411
• Main Authors: Justin Thomas, K. R, Lin, Jiann T, Tao, Yu-Tai, Ko, Chung-Wen
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 26.09.2001; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Physical Sciences; Science & Technology; THERMAL-STABILITY; SUBSTITUTION; POLYMERS; ARYL HALIDES; CHEMISTRY; NITROGEN; EFFICIENT BLUE ELECTROLUMINESCENCE; COPPER; POLY(N-VINYLCARBAZOLE); MOLECULES
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja010819s

Stable carbazole derivatives that contain peripheral diarylamines at the 3- and 6-positions and an ethyl or aryl substituent at the 9-position of the carbazole moiety have been synthesized via palladium-catalyzed C−N bond formation. These new carbazole compounds (carbs) are amorphous with high glass transition temperatures (T g, 120−194 °C) and high thermal decomposition temperatures (T d > 450 °C). The compounds are weakly to moderately luminescent in nature. The emission wavelength ranges from green to blue and is dependent on the substituent at the peripheral nitrogen atoms. Two types of light-emitting diodes were constructed from carb:  (I) ITO/carb/TPBI/Mg:Ag and (II) ITO/carb/Alq3/Mg:Ag, where TPBI and Alq3 are 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene and tris(8-hydroxyquinoline) aluminum, respectively. In type I devices, the carb functions as the hole-transporting as well as emitting material. In type II devices, either carb, or Alq3 is the light-emitting material. Several green light-emitting devices exhibit exceptional maximum brightness, and the physical performance appears to be better than those of typical green light-emitting devices of the structure ITO/diamine/Alq3/Mg:Ag. The relation between the LUMO of the carb and the performance of the light-emitting diode is discussed.