Highly Efficient Green‐Emitting Phosphorescent Iridium Dendrimers Based on Carbazole Dendrons

Green‐emitting iridium dendrimers with rigid hole‐transporting carbazole dendrons are designed, synthesized, and investigated. With second‐generation dendrons, the photoluminescence quantum yield of the dendrimers is up to 87 % in solution and 45 % in a film. High‐quality films of the dendrimers are fabricated by spin‐coating, producing highly efficient, non‐doped electrophosphorescent organic light‐emitting diodes (OLEDs). With a device structure of indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonic acid)/neat dendrimer/1,3,5‐tris(2‐N‐phenylbenzimidazolyl)benzene/LiF/Al, a maximum external quantum efficiency (EQE) of 10.3 % and a maximum luminous efficiency of 34.7 cd A–1 are realized. By doping the dendrimers into a carbazole‐based host, the maximum EQE can be further increased to 16.6 %. The integration of rigid hole‐transporting dendrons and phosphorescent complexes provides a new route to design highly efficient solution‐processable dendrimers for OLED applications.

[1]  Ifor D. W. Samuel,et al.  A Light‐Blue Phosphorescent Dendrimer for Efficient Solution‐Processed Light‐Emitting Diodes , 2005 .

[2]  S. Tokito,et al.  Organic Light-Emitting Diodes Using Multifunctional Phosphorescent Dendrimers with Iridium-Complex Core and Charge-Transporting Dendrons , 2005 .

[3]  Carsten Rothe,et al.  Carbazole compounds as host materials for triplet emitters in organic light-emitting diodes: polymer hosts for high-efficiency light-emitting diodes. , 2004, Journal of the American Chemical Society.

[4]  Yuh-Sheng Wen,et al.  Highly Phosphorescent Bis-Cyclometalated Iridium Complexes Containing Benzoimidazole-Based Ligands , 2004 .

[5]  Charlotte K. Williams,et al.  Solution-processible conjugated electrophosphorescent polymers. , 2004, Journal of the American Chemical Society.

[6]  A. van Dijken,et al.  Carbazole compounds as host materials for triplet emitters in organic light-emitting diodes: tuning the HOMO level without influencing the triplet energy in small molecules. , 2004, Journal of the American Chemical Society.

[7]  E. Namdas,et al.  Solution‐Processable Red Phosphorescent Dendrimers for Light‐Emitting Device Applications , 2004 .

[8]  Xiabin Jing,et al.  Novel hole-transporting materials based on 1,4-bis(carbazolyl)benzene for organic light-emitting devices , 2004 .

[9]  H. Bässler,et al.  Charge transport in highly efficient iridium cored electrophosphorescent dendrimers , 2004 .

[10]  E. Namdas,et al.  Synthesis and properties of highly efficient electroluminescent green phosphorescent iridium cored dendrimers , 2003 .

[11]  Akira Tsuboyama,et al.  Homoleptic cyclometalated iridium complexes with highly efficient red phosphorescence and application to organic light-emitting diode. , 2003, Journal of the American Chemical Society.

[12]  Fumio Sato,et al.  High-efficiency phosphorescent polymer light-emitting devices , 2003 .

[13]  M. Thompson,et al.  Phosphorescence quenching by conjugated polymers. , 2003, Journal of the American Chemical Society.

[14]  Sergey Lamansky,et al.  Synthesis and characterization of facial and meridional tris-cyclometalated iridium(III) complexes. , 2003, Journal of the American Chemical Society.

[15]  N. McClenaghan,et al.  Ruthenium(II) dendrimers containing carbazole-based chromophores as branches. , 2003, Journal of the American Chemical Society.

[16]  Stephen R. Forrest,et al.  Blue organic electrophosphorescence using exothermic host–guest energy transfer , 2003 .

[17]  Yongmin Liang,et al.  High-efficiency red-light emission from polyfluorenes grafted with cyclometalated iridium complexes and charge transport moiety. , 2003, Journal of the American Chemical Society.

[18]  Ifor D. W. Samuel,et al.  Green Phosphorescent Dendrimer for Light‐Emitting Diodes , 2002 .

[19]  T. Weil,et al.  Shape-persistent, fluorescent polyphenylene dyads and a triad for efficient vectorial transduction of excitation energy. , 2002, Angewandte Chemie.

[20]  Daniel Moses,et al.  High‐Efficiency Polymer‐Based Electrophosphorescent Devices , 2002 .

[21]  Yong Cao,et al.  Highly efficient electrophosphorescent devices based on conjugated polymers doped with iridium complexes , 2002 .

[22]  H. Bässler,et al.  Control of mobility in molecular organic semiconductors by dendrimer generation , 2001 .

[23]  J. Fréchet,et al.  Dendrimer-Containing Light-Emitting Diodes: Toward Site-Isolation of Chromophores , 2000 .

[24]  Jean M. J. Fréchet,et al.  Light-harvesting dendrimers , 2000 .

[25]  S. Forrest,et al.  VERY HIGH-EFFICIENCY GREEN ORGANIC LIGHT-EMITTING DEVICES BASED ON ELECTROPHOSPHORESCENCE , 1999 .

[26]  I. Samuel,et al.  CONJUGATED DENDRIMERS FOR LIGHT-EMITTING DIODES : EFFECT OF GENERATION , 1999 .

[27]  S. Forrest,et al.  Highly efficient phosphorescent emission from organic electroluminescent devices , 1998, Nature.

[28]  Jeffrey S. Moore,et al.  Electroluminescent diodes from a single component emitting layer of dendritic macromolecules , 1996 .

[29]  E. Weitz,et al.  Gas-Phase Photofragmentation of Cr(CO)6: Time-Resolved Infrared Spectrum and Decay Kinetics of “Naked” Cr(CO)5 , 1985 .

[30]  F. A. Neugebauer,et al.  tert.-Butyl-substituierte Carbazole , 1972 .