Synthesis of 2-phenylquinoline-based ambipolar molecules containing multiple 1,3,4-oxadiazole spacer groups

TY - JOUR

T1 - Synthesis of 2-phenylquinoline-based ambipolar molecules containing multiple 1,3,4-oxadiazole spacer groups

AU - Xiang, Neng Jun

AU - Lee, Tik H.

AU - Gong, Meng Lian

AU - Tong, K. L.

AU - SO, Shu Kong

AU - LEUNG, Louis M L

N1 - Funding Information: LML would like to acknowledge the support of this research by the Research Grant Council of Hong Kong (grant #HKBU/2118/03E) and the HKBU (grant #FRG/01-02/II72). MLG acknowledges the support of the Scientific and Technical Projects of Guangdong Province (B10502).

PY - 2006/2/1

Y1 - 2006/2/1

N2 - A 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.

AB - A 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.

KW - 1,3,4-Oxadiazole

KW - 2-Phenylquinoline

KW - Ambipolar fluorescence dyes

KW - Triphenylamine

UR - http://www.scopus.com/inward/record.url?scp=33644553110&partnerID=8YFLogxK

U2 - 10.1016/j.synthmet.2005.12.005

DO - 10.1016/j.synthmet.2005.12.005

M3 - Journal article

AN - SCOPUS:33644553110

SN - 0379-6779

VL - 156

SP - 270

EP - 275

JO - Synthetic Metals

JF - Synthetic Metals

IS - 2-4

ER -