Jiaqi Yu

Improved performance of electroluminescent devices based on an europium complex

Electroluminescent (EL) devices using an europium complex Eu(DBM)3 bath as the electron-transport emitting layer were fabricated. The quenching effect of the metal cathode and the unstable nature of the Eu complex under EL operation markedly influence the EL efficiency. By keeping the emitting area far from the metal cathode and partly doping the Eu(DBM)3 bath layer with a hole-transport material, the EL performance was significantly improved. Sharp-band red emissions with turn-on voltage of 3 V, brightness of 820 cd/m2, and external quantum efficiency of 1% were achieved.

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.

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.

Organic electroluminescent devices using europium complex as an electron-transport emitting layer

Abstract Organic electroluminescent (EL) devices with europium complex Eu(DBM) 3 bath as electron transport emitting layer were fabricated. The devices showed bright red and white EL emissions when PVK and NPB, respectively, were used as the hole transport layer. This imply that Eu(DBM) 3 bath has excellent electron injection and transport properties besides its luminescent performance.

Organic electroluminescent devices using terbium chelates as the emitting layers

Abstract Electroluminescent (EL) devices using a ternary terbium complex [Tb(AcA) 3phen] as emitter have been fabricated. When polyvinylcarbazole is used as the hole-transporting layer (HTL), luminance of 210 cd m−2 with pure Tb3+ EL emissions from the devices is achieved.

Exciplex emissions in bilayer and doped thin films containing a non-fluorescent gadolinium complex

Abstract Bilayer and doped thin films of a non-fluorescent gadolinium complex gadolinium(dibenzoylmethanato) 3 (bathophenanthroline) [Gd(DBM) 3 bath] and N,N ′-diphenyl- N,N ′bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine (TPD) are prepared. The exciplex formation between TPD and Gd(DBM) 3 bath in doped film is confirmed through the measurement of the emission, excitation and absorption spectra. Exciplex emissions in electroluminescent process and the different electroluminescent spectra in the bilayer and the doped films are observed.

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.

Stimulated emission in the blue wavelength region from a copolymer containing PPV segment

The lasing properties of a soluble conjugated polymer, Poly[1,8-octanedioxy-2,6-dimethoxy-1,4-phenylene-1,2-ethenylene-1,2-phenylene-1,2-ethenylene-3,5-dimethoxy-1,4-phenylene] (CNMBC-Ph) in chloroform solution were investigated. The third harmonic radiation of a Nd:YAG laser was used as the pump light. The stimulated emission with a linewidth of 15 nm was observed in the blue wavelength region with the peak at 450 nm. The threshold pulse peak power was about 2.8 MW/cm(2). The energy conversion yield of the laser was estimated to be about 3.4%. The maximum peak power of the laser output pulse reached 40 kW

Redistribution of carriers in OEL devices by inserting a thin charge-carrier blocking layer

Abstract By inserting a thin Gd(AcA) 3 phen layer in the electroluminescent devices ITO/Alq/Al and ITO/TPD/Eu(DBM) 3 phen/Alq/Al, the quantum efficiency is increased in both devices and the emission color of the second device is changed. These results are supposed to be due to the carrier-blocking effect of the thin Gd(AcA) 3 phen layer which changes the distribution of electrons and holes in the devices.

STIMULATED EMISSION IN BLUE WAVELENGTH REGION FROM A COPOLYMER

A dye laser based on the soluble conjugated polymer, Poly[1,8-octanedioxy-2,6-dimethoxy-1,4-phenylene-1,2-ethenylene-1, 4-phenylene-1,2-ethenylene-3,5-dimethoxy-1,4-phenylene], has been fabricated. The laser was pumped by light pulses from the third harmonic radiation of an Nd:YAG laser. The lasing was observed in the blue wavelength region with the peak at 450 nm. The threshold energy is about 19 mu J. The energy conversion yield of the laser is about 3.4%. The maximum peak power of the laser output pulse arrives at about 20 kW.