Chunjun Liang

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.

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.

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.

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.

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.

Infrared electroluminescence of ytterbium complexes in organic light emitting diodes

Abstract A comparison of near infrared (IR) emitting properties among Yb 3+ complexes containing devices was made. Ytterbium (dibenzoylmethanato) 3 (bathophenanthroline) [Yb(DBM) 3 bath] was used as electron-transport and emitting material. N , N ′-diphenyl- N , N ′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD) acted as a hole-transport layer. Utilizing a device of trilayer structure ITO/TPD (40 nm)/Yb(DBM) 3 bath:TPD (weight ratio approx. 1:1, 40 nm)/Yb(DBM) 3 bath (80 nm)/Ag/Mg (150 nm), an intense emission corresponding to the 2 F 5/2 → 2 F 7/2 electronic transition of the trivalent Yb ion, Yb 3+ , was observed from the organic electroluminescent device. Current density dependence on drive voltage revealed good electron injection and transport properties of the Yb(DBM) 3 bath. The tendency of the efficiencies of IR and visible emissions under different current densities was discussed. A broad band at approximately 580 nm was observed in the EL spectrum, which could be assigned to exciplex emission.