Xingyuan Liu

Europium complexes as emitters in organic electroluminescent devices

Abstract Using two different trivalent europium (Eu 3+ ) complexes, europium(dibenzoylmethanato) 3 (bathophenanthroline) [Eu(DBM) 3 bath] and europium (dibenzoylmethanato) 3 (monophenanthroline) [Eu(DBM) 3 phen], with different ligands for emission-layer materials, various types of electroluminescent (EL) devices have been fabricated. Combined with a triphenylamine derivative (TPD) and an oxadiazole derivative (OXD7) as hole-transport-layer materials, two-layer- and three-layer-type devices have been fabricated. We find that these two emission-layer materials have similar EL spectra, but their EL performances are different. The EL capability of the Eu complexes and their carrier-transporting characteristics are largely dependent on the ligands.

Heterocycle-substituted poly (p-phenylene vinylene) for light-emitting devices

Abstract Results are presented which explore the synthesis, characterization and electroluminescence performance of a new type of conjugated polymer, poly(2,5-diphenyl-1,3,4-oxadiazolyl)-4,4′-vinylene (O-PPV). A light-emitting diode consisting of ITO/O-PPV/Al is driven at about 6 V and has a peak emission wavelength of 483 nm, and this is in agreement with the result determined by the X-ray photoelectron spectroscopy (XPS) technique.

White light emitting organic electroluminescent devices using lanthanide dinuclear complexes

Abstract Organic electroluminescent devices with Eu x Tb 1− x (aca) 3 phen dinuclear complex as the emitting layer were fabricated. When the devices are operated under proper voltage the white light can be obtained. It consists of three parts: red from Eu 3+ , green from Tb 3+ and blue from TPD (or NPB).

Enhanced electroluminescence of europium(III) complex by terbium(III) substitution in organic light emitting diodes

Abstract A binuclear complex Tb0.5Eu0.5(aca)3phen was synthesized and used as the emission material. It was found that there is an efficient energy transfer from Tb3+ to Eu3+ in the emitting layer.

Spectrally-narrow blue light-emitting organic electroluminescent devices utilizing thulium complexes

Abstract Organic electroluminescent (OEL) devices with trivalent thulium (Tm 3+ ) complex (Tm(acetylacetonato) 3 (monophenanthroline) [Tm(AcA) 3 phen]) as an emitting layer were fabricated. Double-layer type cells with a structure of glass substrate/indium–tin oxide (ITO)/poly-(vinylcarbazole) (PVK)/Tm complex/Al exhibit blue luminescence when forward bias dc voltage was applied. Spectrally-narrow OEL emission at 482 nm from Tm 3+ ion in Tm complex was observed.

Energy transfer process from polymer to rare earth complexes

Abstract The interaction between poly( N -vinylcarbazole) (PVK) and rare earth (RE) complexes, such as Eu(thenoytrifluoacetonato) 4 -(monopyridinium) (Eu(TTA) 4 Py). Eu(nitrate) 3 (monophenanthroline) (Eu(NO 3 ) 3 phen) and Tb(acetylacetonato) 3 (monophenanthroline) (Tb(AcA) 3 phen), was investigated in solution as well as in films using the photoluminescence (PL) spectrum. In chloroform solution, the fluorescent intensity of the Eu(NO 3 ) 3 phen was enhanced by PVK; however, the fluorescent intensity of the Tb complex was greatly quenched by PVK. Strongly characteristic emissions of Eu 3+ and Tb 3+ were observed in Eu and Tb complex-dispersed PVK films, respectively. The excitation spectra of Eu complex-dispersed PVK films and Tb complex-dispersed PVK film are very similar to that of the pure PVK film, indicating that effective energy transfer occurs from PVK to the RE complexes. Based on the above experimental results, three types of organic electroluminescence (EL) devices with structure of ITO/Eu(NO 3 ) 3 phen:PVK/OXD-7/Al, ITO/Eu(TTA) 4 Py:PVK/OXD-7/Al and ITO/ Tb(AcA) 3 phen:PVK/OXD-7/Al (ITO = indium-tin oxide) were fabricated. Bright red emission can be observed in the first and second devices while bright green light was emitted from the latter device.

White light emission from OEL devices based on organic dysprosium-complex

Trivalent dysprosium ion (Dy 3+ ) complex with a structure of Dy(acetylacetonato) 3 phenanthroline (Dy(AcA) 3 phen) was synthesized and used as an emitting material in organic electroluminescence (OEL) devices from which a white light emission was observed. A double-layer OEL device with a structure of PVK (100 nm)/Dy-complex (70 nm) was fabricated. The white emission consisted of a yellow band (∼ 580 nm) and a blue emission band (∼ 480 nm) corresponding to the 4 F 9/2 → 6 H 13/2 transition and 4 F 9/2 → 6 H 15/2 transition of Dy 3 + ion in the complex, respectively.

Organic Light-Emitting Diode Using Eu3+ Polymer Complex as an Emitter

A new fluorescent Eu3+ polymer complex with the trivalent europium (Eu3+) ion directly bonded to a polymer chain was synthesized, and a new organic electroluminescent (EL) device in which it is used as the emitting layer was fabricated successfully for the first time. It was found that the EL and PL spectra of the device and its film were different from each other; for the former, the emission peaks lie at 595 nm and 657 nm, while it is at 618 nm for the latter. The difference between EL and PL was also discussed.

Electron-transport properties of rare earth chelates in organic electroluminescent devices

Abstract Electron-transporting properties of a series of trivalent rare earth ion (RE 3+ ) complexes in multilayer organic electroluminescent (OEL) devices have been studied. The emitting layer (EML) in the devices consists of trivalent europium (Eu 3+ ) complexes dispersed into PVK [poly( N -vinylcarbazole)] film.

Electroluminescent properties of naphthalimide derivative thin film devices

Abstract N -alkyl or arenyl-4-acetylamide-1,8-naphthalimides (NA) were synthesized by reaction of 4-acetylamide-1,8-naphthalic acid with organic amines. Optical properties were studied in the UV-visible region. By using Joule evaporation thin films of the NA, the double layer of EL devices (ITO/PVK/NA/Al) were fabricated. Yellow and green EL emission at around 569.0–504.2 nm was observed. It was found that the emission wavelength of the devices using naphthalimides with bulkier N -alkyl groups shifted to red while the emission wavelength of those devices using naphthalimides with N -arenyl substituted groups shifted to blue. This is identified with the results calculated by the MINDO/3 model. Moreover, experimental results revealed that the Joule heat by non-radiative decay has a significant affect on the device life, and the life of the device using naphthalimide compounds with high melting points is longer than that of the device fabricated using those with low melting points.