Four monodisperse starburst oligomers bearing a 4,4′,4″‐tris(carbazol‐9‐yl)‐triphenylamine (TCTA) core and six oligofluorene arms are synthesized and characterized. The lengths of oligofluorene arms vary from one to four fluorene units, giving the starburst oligomers molecular weights ranging from 3072 to 10 068 Da (1 Da = 1.66 × 10–27 kg). All of the starburst oligomers have good film‐forming capabilities, and display bright, deep‐blue fluorescence (λmax = 395–416 nm) both in solution and in the solid state, with the quantum efficiencies of the films (ΦPL) varying between 27 and 88 %. Electrochemical studies demonstrate that these materials have large energy gaps, and are stable for both p‐doping and n‐doping processes. Electroluminescent devices are successfully fabricated using these materials as hole‐transporting emitters, and emit deep‐blue light. Devices with luminance values up to 1025 cd m–2 at 11 V and luminous efficiencies of 0.47 cd A–1 at 100 cd m–2 have been produced, which translates to an external quantum efficiency of 1.4 %. In addition, these large‐energy‐gap starburst oligomers are good host materials for red electrophosphorescence. The luminance of the red electrophosphorescent devices is as high as 4452 cd m–2, with a luminous efficiency of 4.31 cd A–1 at 15 mA cm–2: This value is much higher than those obtained from the commonly used hole‐transporting materials, such as poly(vinyl carbazole) (PVK) (1.10 cd A–1 at 16 mA cm–2).

Three phosphorescent dendrimers (IrC1, IrC3, and IrF2) with an iridium complex core and oligocarbazole or oligofluorene substituted ligands were synthesized and characterized. The structures of the oligocarbazole were designed to maintain high triplet energy of the ligands so that phosphorescence quenching in the resulting dendrimers can be prevented, while the oligofluorene in IrF2 resulted in undesired phosphorescence quenching. Best performance was obtained from an IrC3 based electrophosphorescent light‐emitting device with a maximum luminance of 13 060 cd · m−2 at a driving voltage of 11.5 V and a peak current‐efficiency of 4.3 cd · A−1 at a luminance of 3 400 cd · m−2, owing to its high PL efficiency, and efficient energy transfer between the iridium complex core and the ligands.magnified image