Siheung, South Korea
Siheung, South Korea

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Jang S.E.,Dankook University | Joo C.W.,Dankook University | Yook K.S.,Dankook University | Kim J.-W.,OLED Team | And 2 more authors.
Synthetic Metals | Year: 2010

Thermally stable blue organic light-emitting diodes (OLEDs) were developed using anthracene based host materials with a spirobifluorene group. 4-Bromospirobifluorene and 2-bromospirobifluorene were attached to the anthracene core and the effect of the substitution position on the physical properties and device performances of the blue fluorescent OLEDs was investigated. The 4-spirobifluorene substitution was better than the 2-spirobifluorene substitution in terms of thermal stability and widened the bandgap of the anthracene based host material due to the geometrical structure of the material. However, the wide bandgap of the host material with 4-spirobifluorene had negative effect on the current density and efficiency of the blue devices. © 2010 Elsevier B.V. All rights reserved.

Jeon Y.-M.,Dankook University | Lee J.-Y.,Dankook University | Kim J.-W.,OLED Team | Lee C.-W.,OLED Team | Gong M.-S.,Dankook University
Organic Electronics: physics, materials, applications | Year: 2010

The deep blue fluorescent spiro-type dopant materials N,N,N′, N′-tetraphenylspiro[fluorene-7,9′-benzofluorene] (SFBF)-5,9-diamine (BD-6DPA), N,N′-di-(2-naphthyl)-N,N′-diphenyl-SFBF-5,9-diamine (BD-6NPA), N,N′-diphenyl-N,N′-di-m-tolyl-SFBF-5,9-diamine (BD-6MDPA) and N,N′-diphenyl-N,N′-bis(4-(trimethylsilyl)phenyl)-SFBF-5,9- diamine (BD-6TMSA) were designed and successfully prepared by amination reactions. The EL characteristics of MADN as the blue host material doped with the above blue dopant materials were evaluated. The electroluminescence spectra of ITO/N,N′-diphenyl-N,N′-bis-[4-(phenyl-m-tolyl-amino)-phenyl]- biphenyl-4,4′-diamine (DNTPD/N,N′-di(1-naphthyl)-N,N′- diphenylbenzidine (NPB)/2-methyl-9,10-di(2-naphthyl)anthracene (MADN):BD-6MDPA/tris(8-hydroxyquinoline)aluminum (Alq3)/LiF/Al devices show a narrow emission band with a full width at half maximum of 48 nm and a λmax() = 463 nm. The device obtained from MADN doped with BD-6MDPA showed a good color purity (0.135, 0.156), high luminance efficiency (9.11 cd/A at 6.5 V) and high external quantum efficiency (8.16%). © 2010 Elsevier B.V. All rights reserved.

Jeon Y.-M.,Dankook University | Lee I.-H.,Dankook University | Lee C.-W.,Dankook University | Lee J.-Y.,OLED Team | Gong M.-S.,Dankook University
Bulletin of the Korean Chemical Society | Year: 2010

Spiro-type orange phosphorescent host materials, 9-diphenylphosphine oxide-spiro[fluorene-7,9'-benzofluorene] (OPH-1P) and 5-diphenylphosphine oxide-spiro[fluorene-7,9'-benzofluorene] (OPH-2P) were successfully prepared by a lithiation reaction followed by a phosphination reaction with diphenylphosphinic chloride. The EL characteristics of OPH-1P and OPH-2P as orange host materials doped with iridium(III) bis(2-phenylquinoline) acetylacetonate (Ir(pq)2acac) were evaluated. The electroluminescence spectra of the ITO (150 nm)/DNTPD (60 nm)/NPB (30 nm)/OPH-1P or OPH-2P: Ir(pq)2acac (30 nm)/BCP (5 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (200 nm) devices show a narrow emission band with a full width at half maximum of 75 nm and λmax = 596 nm. The device obtained from OPH-1P doped with 3% Ir(pq)2acac showed an orange color purity of (0.580, 0.385) and an efficiency of (14 cd/A at 7.0 V). The ability of the OPH-P series to combine a high triple energy with a low operating voltage is attributed to the inductive effect of the P=O moieties and subsequent energy lowering of the LUMO, resulting in the enhancement of both the electron injection and transport in the device. The overall result is a device with an EQE > 8% at high brightness, but operating voltage of less than 6.4 V, as compared to the literature voltages of ∼10 V.

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