Synthesis of 2-phenylquinoline-based ambipolar molecules containing multiple 1,3,4-oxadiazole spacer groups
2006; Elsevier BV; Volume: 156; Issue: 2-4 Linguagem: Inglês
10.1016/j.synthmet.2005.12.005
ISSN1879-3290
AutoresNeng Jun Xiang, Tik H. Lee, Meng Lian Gong, K.L. Tong, Shu Kong So, Louis M. Leung,
Tópico(s)Conducting polymers and applications
ResumoA series of donor–acceptor type ambipolar electroluminescence dyes with the general structure PQ(OXD)nT (where n = 1, 2 and 3) were prepared, in which PQ is 2-phenylquinoline, T is diphenylamine which constituted the hole transporting triphenylamine moiety with an adjacent phenyl ring, and OXD is an electron transporting 2-phenyl-1,3,4-oxadiazole repeating unit. The compounds fluoresced bluish green to green hue in solid-state, exhibited a positive solvatochromism in solution and their quantum efficiency decreased rapidly with increase in n. The materials are thermally stable with glass transition temperature (Tg) ranging from 83 °C (n = 1) to 130 °C (n = 3). Cyclic voltammetry studies indicated the HOMO remained relatively unchanged with n while the LUMO decreased (away from the vacuum level) with an increase in the number of OXD. For single layer homojunction OLEDs, highest efficiency was obtained when n = 1 (max luminous 3300 cd/m2 and current efficiency 0.9 cd/A), whereas for multilayer heterojunction OLEDs, best results was achieved for compounds with n = 1 or 2 assuming the role of the HT layer (over 8200 cd/m2 max and 2.0 cd/A). Formation of exciplexes led to significant red-shift and lower emission efficiency for the compound with n = 3.
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