Ziruo Hong

A bis-salicylaldiminato Schiff base and its zinc complex as new highly fluorescent red dopants for high performance organic electroluminescence devices

Schiff base 2,3-bis[(4-diethylamino-2-hydroxybenzylidene)amino]but-2-enedinitrile (BDPMB) and its zinc complex (BDPMB-Zn) with donor–acceptor–donor (D–A–D) type ICT properties in the neutral form were used as novel red-emitting dopants in OLEDs; bright saturated red-emitting EL devices with excellent colour chromaticity coordinates (x, y = 0.670, 0.325 for BDPMB; x, y = 0.655, 0.325 for BDPMB-Zn) and good efficiency (1.35 cd A−1 for BDPMB; 0.50 cd A−1 for BDPMB-Zn) were obtained.

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.

1.4 μm band electroluminescence from organic light-emitting diodes based on thulium complexes

Near-infrared (NIR) electroluminescence (EL) devices have been fabricated employing thulium complexes as emitting materials. The EL emissions at 1.4 and 0.8 μm were observed from the devices of tris-(dibenzoylmethanato)-mono-(bathophenanthroline or 1,10-phenonthroline) thulium [Tm(DBM)3bath or Tm(DBM)3phen] at room temperature and assigned to 3F4–3H4 and 3F4–3H6 transitions of Tm3+ ions, respectively. By comparison with the NIR emissions of four Tm complexes with different ligands, it was found that the first ligand played a more important role for the Tm3+ ion emissions rather than the second one. In order to meet the requirement of optical communication, both Tm(DBM)3bath and erbium [Er] (DBM)3bath were incorporated into EL devices so that a broadened EL emission band ranging from 1.4 to 1.6 μm was obtained, showing the potential application of Tm complexes for optical communication systems.

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).

Synthesis, photoluminescence and electroluminescence of new 1H-pyrazolo[3,4-b]quinoxaline derivatives

Several new 1H-pyrazolo[3,4-b]quinoxaline derivatives with N,N-dialkylamino electron-donating groups were prepared; their photoluminescence in solution and electroluminescence in thin-film devices have been investigated. They show emission at 520–540 nm with a fluorescence quantum yield close to unity in moderately polar solvents. The absorption and emission maxima shift to red with increasing solvent polarity. The fluorescence quantum yield also increases with increasing solvent polarity from non-polar to moderately polar solvents, then decreases slightly with further increase of solvent polarity. It indicates that both “positive” and “negative” solvatokinetic effects co-exist. The electroluminescence of OLED devices fabricated by using these compounds as dopants was investigated. All devices with the configuration of indium–tin oxide coated glass/NPB (60 nm)/Alq3 : Dopant (30 nm)/Alq3 (20 nm)/Mg : Ag (200 nm) show bright green emission with efficiencies of 7.5–9.7 cd A−1 and narrow full bandwidth at half intensity of 68–75 nm peaking at 536–552 nm.

Bifunctional photovoltaic and electroluminescent devices using a starburst amine as an electron donor and hole-transporting material

Photovoltaic (PV) devices, using 4,4′,4″-tris(2-methylphenylphenylamino)triphenylamine (m-MTDATA) as an electron donor and tris-(8-hydroxyquinoline) aluminum (Alq) as an electron acceptor, were fabricated. The relationship between photocurrent generation, exciplex formation, and device structure was explored. PV performance was significantly enhanced by inserting a thin mixed layer (5 nm) of m-MTDATA and Alq between the two organic layers of the original m-MTDATA/Alq bilayer device. Both the bilayer and trilayer devices showed PV and electroluminescent (EL) properties, suggesting their potential use as multifunction devices. It was also shown that strong EL emission from exciplex might be used as an indicator of efficient exciton dissociation during the reverse PV process.

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.

Organic-film photovoltaic cell with electroluminescence

An organic-film photovoltaic (PV) cell, in which N,N′-bis-(1-naphthyl)- N,N′- diphenyl- 1,1′- biphenyl-4,4′-diamine (NPB) and tris(acetylacetonato)-(monophenothroline) yttrium [Y(ACA)3phen] were used as electron-acceptor and donor, respectively, has been fabricated. Under UV light (4 mW/cm2), the short-circuit current (Isc), open-circuit voltage (Voc), fill factor (FF) and the overall power conversion efficiency of the optimum PV cell were 46 μA/cm2, 2.15 V, 0.30%, and 0.7%, respectively. The photocurrent response region of the cell parallels the adsorption of NPB. The PV effect is attributed to exciplex formation at the interface between the two organic films. The PV cell described displays electroluminescence (EL) emission of blue light upon application of a dc voltage. The maximum luminance was 750 cd/m2 at 15 V driving voltage.

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.