Details

Autor(en) / Beteiligte

• Xu, Hui
• Yu, Dong-Hui
• Liu, Le-Le
• Yan, Peng-Fei
• Jia, Li-Wei
• Li, Guang-Ming
• Yue, Zheng-Yu

Titel

Small Molecular Glasses Based on Multiposition Encapsulated Phenyl Benzimidazole Iridium(III) Complexes: Toward Efficient Solution-Processable Host-Free Electrophosphorescent Diodes

Ist Teil von

• The journal of physical chemistry. B, 2010-01, Vol.114 (1), p.141-150

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2010

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Three electrophosphorescent small molecular Ir3+ complexes, Ir(HexPhBI)3 1 (HexPhBI = 1-Hexyl-2-phenyl-1H-benzo[d]imidazole), Ir(CzPhBI)3 2 (CzPhBI = 9-(6-(2-phenyl-1H-benzo[d]imidazol-1-yl)hexyl)-9H-carbazole), and Ir(Cz2PhBI)3 3 (Cz2PhBI = 9-(6-(4-(1-(6-(9H-carbazol-9-yl)hexyl)-1H-benzo[d]imidazol-2-yl)phenoxy)hexyl)-9H-carbazole), were synthesized in which 3 was designed with the structure of multiposition encapsulation. Compared to the hexyl-substituted 1, 2 and 3 end-capped with the conjugated carbazole moieties have improved thermal stability. X-ray diffraction analysis proved the amorphous state of 2 and 3. High-photoluminescent efficiencies of 3 are achieved as 72% in solution and 61% in solid. It indicates that the peripheral carbazoles not only facilitate the separation of triplet-emission cores and reduce the intermolecular aggregation but also supply a routine for the intermolecular energy transfer. Electrochemical analysis showed the more oxidation states of 3, which might be anticipated to make it superior to 1 and 2 in hole injection and transporting. The important role of the peripheral carbazole moieties in carrier injection/transporting and the optical properties of the complexes were further investigated by Gaussian simulation. A dramatic electroluminescent (EL) performance, including external quantum efficiency of nearly 6%, low turn-on voltage of 2.5 V, and high brightness over 6000 cd m−2, from the host-free spin-coated device of 3 was achieved. The superiority of multiencapsulation in EL was proved by comparing the EL performance of 2 and 3. By making comparison between the host-free and phosphor-doping devices, it indicated that the combined modification of the aliphatic chains and functional groups in multipositions is a feasible approach to realize the high-efficiency small molecular phosphorescent materials.