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44 results on '"Liu, Michelle S."'

7. Bright and efficient exciplex emission from light-emitting diodes based on hole-transporting amine derivatives and electron-transporting polyfluorenes.

Author

Jiang, Xuezhong, Liu, Michelle S., and Jen, Alex K.-Y.

Subjects
*LIGHT emitting diodes, *AMINES
Abstract

We report highly efficient and bright emission from exciplexes generated between a series of hole-transporting amine derivatives and two electron-transporting fluorene-dicyanophenyl (FCNP) copolymers. These exciplexes were formed at either the interface between tetraphenyldiamine-containing perfluorocyclobutane polymers and the FCNP copolymers, or in the blends of the FCNP copolymers with small molecule amine derivatives such as triphenylamine, N,N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine, and N,N′-diphenyl-N,N′-bis(1-naphthyl)-[1,1′-biphenyl]-4,4& prime;-diamine. The exciplex emission is largely dependent on the composition of the hole-transporting materials. The best device derived from these exciplexes demonstrated a very low turn-on voltage (2.8 V), a high external quantum efficiency (0.91%), and a high brightness of 3370 cd/m². The desirable properties of these devices were attributed to the excellent electron transport ability of the FCNP copolymers. [ABSTRACT FROM AUTHOR]

Published
2002
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8. Time resolved photoluminescence spectroscopy of surface-plasmon-enhanced light emission from conjugate polymers

Author

Neal, Terrell D., Okamoto, Koichi, Scherer, Axel, Liu, Michelle S., Jen, Alex K.-Y., Neal, Terrell D., Okamoto, Koichi, Scherer, Axel, Liu, Michelle S., and Jen, Alex K.-Y.

Abstract

The authors have experimentally verified that the light emission from conjugated polymers can be enhanced through the use of surface plasmon coupling layers. Carrier dynamics of such plasmon-enhanced organic light emitters were studied and a recombination rate increase due to surface plasmon polaritons was experimentally observed. Internal quantum efficiency data from the polyfluorenes studied follow the trend supported by the time resolved photoluminescence measurements.

Published
2006

42. Lithium salt doped conjugated polymers as electron transporting materials for highly efficient blue polymer light-emitting diodes.

Author

Fei Huang, Ping-I Shih, Liu, Michelle S., Ching-Fong Shu, and Jen, Alex K.-Y.

Subjects
POLYMERS, LIGHT emitting diodes, SOLID freeform fabrication, FLUORENE, ELECTRON transport, DOPED semiconductors
Abstract

Highly efficient blue polymer light-emitting diodes (PLEDs) are fabricated using a conjugated polymer, poly[9,9-bis(2-(2-(2-diethanol-amino-ethoxy) ethoxy) ethyl) fluorene-alt-4, 4′-phenylether] as an electron transporting layer (ETL). It was found that the performance of these blue-emitting devices could be greatly improved if the ETL was doped with LiF or Li2CO3 salts. A bis[(4,6-di-fluorophenyl)-pyridinato-N, C2] (picolinate) Ir(III) (FIrpic) complex based blue phosphorescent PLED exhibited a maximum luminance efficiency of 20.3 cd/A with a luminance of 1600 cd/m2 at the current density of 7.9 mA/cm2 and drive voltage of 8.0 V. [ABSTRACT FROM AUTHOR]

Published
2008
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43. Thermally crosslinked hole-transporting layers for cascade hole-injection and effective electron-blocking/exciton-confinement in phosphorescent polymer light-emitting diodes.

Author

Yu-Hua Niu, Liu, Michelle S., Jae-Won Ka, and Jen, Alex K.-Y.

Subjects
*EXCITON theory, *ELECTRON transport, *LIGHT emitting diodes, *CROSSLINKING (Polymerization), *ELECTRODES, *SPECTROMETERS
Abstract

A bilayer hole-injection/transport structure was prepared by thermally crosslinking two separate hole-transport layers (HTL). The resulting films possess excellent optical quality and solvent resistance. Cascade hole-injection and effective electron-blocking/exciton confinement can be achieved for light-emitting diodes (LEDs) using blue phosphorescent emitters, such asbis(4′,6′-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate. The first HTL was based on tetraphenyldiamine (TPD) has its highest occupied molecular orbit (HOMO) level lies at -5.3 eV, and the second HTL with 4,4′,4″-tri(N-carbazolyl)triphenylamine has its HOMO level lies at -5.7 eV. The preliminary results from blue LEDs using these cascade HTLs showed much improved device performance than those only use a single layer hole-transporting polymer. [ABSTRACT FROM AUTHOR]

Published
2006
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44. Efficient and stable blue light-emitting diodes based on an anthracene derivative doped poly(N-vinylcarbazole).

Author

Yu-Hua Niu, Baoquan Chen, Tae-Dong Kim, Liu, Michelle S., and Jen, Alex K.-Y.

Subjects
LIGHT emitting diodes, BLUE light, ANTHRACENE, POLYCYCLIC aromatic hydrocarbons, DOPED semiconductors, LIGHT sources
Abstract

Single-layer blue light-emitting diodes (LEDs) are fabricated by spin coating a blend of 9,10-bis(3′,5′-diaryl)phenyl anthracene in poly(N-vinylcarbazole) (PVK) or in the mixture of PVK and an electron-transporting molecule, 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole. The Commission Internationale de I’Eclairage coordinates of the resulting LEDs are very close to that of the blue standard from the National Television Standards Committee. These devices also show excellent color stability when operated at a voltage span from 6 to 22 V. High external quantum efficiency (>1.5%) and brightness (>3000 cd/m2) can be obtained in these devices. [ABSTRACT FROM AUTHOR]

Published
2004
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