C.H. Huang

Carbazole-functionalized europium complex and its high-efficiency organic electroluminescent properties

A complex tris(dibenzoylmethanato){1-ethyl-2-(N-ethyl-carbazole-yl-4) imidazo[4,5-f]1,10phenanthroline} europium(III) [Eu(DBM)3phencarz] functionalized by a hole-transport group carbazole was synthesized. Devices using this complex as emitter showed greatly enhanced performance benefited from the increased hole-transport properties and efficient energy transfer from carbazole to the central ions. A 58-nm-single-layer device gave a brightness of 20u2009cd/m2 at 15 V. The highest power efficiency of 2.7 lm/W at 5 V and 0.5u2009cd/m2 and the luminance exceeding 2000 cd/m2 at 20 V was obtained from a device with the configuration of ITO/TPD(20 nm)/Eu(DBM)3phencarz(40 nm)/BCP(20 nm)/AlQ(40 nm)/Mg0.9Ag0.1(200 nm)/Ag(80 nm).

Bright red light-emitting electroluminescence devices based on a functionalized europium complex

The complex tris(dibenzoylmethanato)(1-ethyl-2-(4′-carbazole-9-yl)phenyl imidazo[4,5-f]1,10- phenanthroline) europium (III), Eu(DBM)3(CPIP), was newly synthesized. Devices using this complex as emitter showed greatly enhanced performance benefiting from the improved hole-transporting properties of the complex and good stability. A double-layer device with the configuration of ITO/TPD(50 nm)/Eu(DBM)3(CPIP)(60 nm)/Mg0.9Ag0.1(200 nm)/Ag(80 nm) exhibited Eu3+ based pure red emission with a brightness of 537 cd m−2 at 13 V and the power efficiency of 0.089 lm W−1 at 6 V, 33 cd m−2. A triple-layer device with the configuration of ITO/TPD(40 nm)/Eu(DBM)3(CPIP)(30 nm)/Eu(DBM)3 Bath(50 nm)/Mg0.9Ag0.1 n(200 nm)/Ag (80 nm) also emitted pure red light with a highest brightness of 1050 cd m−2 at 16 V and the highest power efficiency of 0.50 lm W−1 at 8 V, 8 cd m−2. The highest brightness 1460 cd m−2 at 14 V was obtained from a four-layer device with the configuration of ITO/TPD(40 nm)/Eu(DBM)3(CPIP)(40 nm)/BCP(20 nm)/AlQ(10 nm)/Mg0.9Ag0.1(200 nm)/Ag(80 nm) and the highest power efficiency of 0.54 lm W−1 at 7 V, 56 cd m−2.

Carrier-transport, photoluminescence, and electroluminescence properties comparison of a series of terbium complexes with different structures

A series of terbium complexes with different structures revealed different carrier-transport and photophysical properties. Complex A [tris(1-phenyl-3-methyl-4-isobutyl-5-pyrazolone)-bis(triphenyl phosphine oxide), Tb(PMIP)3(TPPO)2] had overly strong electron-transport properties, complex B [Tb(PMIP)3(EtOH)(H2O)] mainly revealed hole-transport properties, and complex C [tris(1-phenyl-3-methyl-4-(2-ethylbutyryl)-5-pyrazolone) triphenyl phosphine oxide, Tb(eb-PMP)3(TPPO)] showed both electron- and hole-transport properties. Their PL intensity ratio was A−B−C = 2.6:1:1.2. The eletroluminescence (EL) performances (brightness and peak power efficiency) achieved from complexes A, B, and C were 9600 cd/m2 and 5.21 lm/W, 2800 cd/m2 and 2.61 lm/W, and 12000 cd/m2 and 11.3 lm/W, from device configurations of ITO/TPD−B−A−AlQ−Mg0.9Ag0.1−Ag (20:20:50:30:200:80 nm), ITO/TPD−B−BCP−AlQ−Mg0.9Ag0.1)−Ag (40:30:20:20:200:80 nm), and ITO/NPB−C−BCP−AlQ−Mg0.9Ag0.1−Ag (10:50:20:40:200:80 nm), respectively. Results indicated that ...

High-performance blue electroluminescent devices based on 2-(4-biphenylyl)-5-(4-carbazole-9-yl)phenyl-1,3,4-oxadiazole.

An electron transporting moiety (1,3,4-oxadiazole) and a hole transporting moiety (carbazole) were combined to create 2-(4-biphenylyl)-5-(4-carbazole-9-yl)phenyl-1,3,4-oxadiazole (CzOxa), a three layer device with a configuration of ITO/TPD(50 nm)/CzOxa(40 nm)/AlQ(40 nm)/Mg0.9Ag0.1(200 nm)/Ag(80 nm) which exhibited a blue emission peak at approximately 470 nm (x = 0.14, y = 0.19) with a maximum luminance of 26,200 cd m(-2) at a drive voltage of 15 V and a maximum luminous efficiency of 2.25 lm W(-1).

In situ visible spectroscopy of a gadolinium bisphthalocyanine LB film exposed to chlorine gas

Abstract We report the preparation of Langmuir-Blodgett (LB) films of a gadolinium phthalocyanine, doubledecker, molecular sandwich-type complex [Gd(Pc) 2 ] and its ultraviolet-visible spectroscopic characterisation. We have studied the changes in the optical absorbance spectra that occur upon exposure to very low concentrations (~10 ppm) of chlorine gas. The main absorption band in the visible region occurs at ~690 nm. Upon exposure to chlorine gas, the intensity of this band decreases with the simultaneous introduction of a new peak at ~734 nm, an isosbestic point occurring at 721 nm. These spectral changes are indicative of oxidation of the complex by chlorine to form the [Gd(Pc) 2 ] + species. The kinetics of this response suggest that the adsorption of chlorine by the LB film is a complex process, possibly involving up to three independent mechanisms. The LB film recovers almost fully (> 95%) upon switching off the chlorine supply.

Photoluminescence and electroluminescence of the exciplex formed between a terbium ternary complex and N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine

We demonstrate the photoluminescence (PL) and electroluminescence (EL) of the exciplex formed between a terbium complex tris-(1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone)-1,10-phenanthroline-terbium Tb(PMIP)3(Phen) and the hole-transporting material N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine (TPD). Experimental results show that a new emission peaking at 540 nm from their 1 : 1 mixture and the electroluminescence from the double layer device (ITO/TPD/Tb(PMIP)3(Phen)/Mg0.9Ag0.1) can be assigned to the exciplex formed between the excited state of TPD and the ground state of the terbium complex. By suppressing the formation of the exciplex by changing the carrier combination zone, pure green light from the central terbium ion with highest brightness 250 cd m−2 at 15 V, power efficiency of 0.31 lm W−1 and turn-on voltage as low as 3 V can be obtained from a device of ITO/TPD(10 nm)/Tb(PMIP)3(Phen)(80 nm)/BCP(20 nm)/Mg0.9Ag0.1. By doping TPD into the emitting layer, which facilitates the exciplex formation, bright yellow emission with highest brightness 1180 cd m−2 at 17 V was obtained from a device of ITO/TPD(20 nm)/Tb(PMIP)3(Phen) : TPD(2 : 1)(50 nm)/Tb(PMIP)3(Phen)(20 nm)/AlQ(30 nm)/Mg0.9Ag0.1.

Study of a novel C60−2,6‐bis(2,2‐bicyanovinyl)pyridine complex thin film

A novel complex thin film of 2,6‐bis(2,2‐bicyanovinyl)pyridine (BDCP) and C60 has been fabricated by vacuum coevaporation of BDCP and C60 from two different evaporation sources. The C60‐BDCP thin films have shown totally different optical and electronic properties from the films of both the BDCP and C60. Stable and reproducible electric bistable properties have been observed in sandwichlike device Ag/C60‐BDCP/Ag. The films are characterized by several methods including high‐resolution scanning electron microscopy, x‐ray diffraction, UV‐visible absorption and infrared transmission spectroscopy.

Photoluminescence and electroluminescence properties of three ternary lutetium complexes

Three lutetium complexes, Lu(PMIP)3(TPPO)2 n(A), Lu(PMIP)3Bipy (B) and Lu(PMIP)3Phen (C) n(where PMIP, TPPO, Bipy and Phen stand for 1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone, triphenylphosphinoxide, 2,2′-bipyridine and 1,10-phenanthroline, respectively), were synthesized and complex A was characterized by single-crystal X-ray diffraction analysis. Complex A was found to crystallize in the P21/n n(14) space group. The photoluminescence spectra of the complexes reveal that all the complexes have a similar spectrum peaking near 440 nm; however, the intensity of the spectrum of complex A is about 100 times higher than that of the other two complexes. When these complexes were utilized to prepare light-emitting devices, that with complex A gave a blue light, originating from this complex, with the highest brightness of 119 cdxa0m−2 at an applied voltage of 19 V, while the same configuration devices using the other two complexes exhibited green light peaking at 512 nm, which arises from exciplexes formed at the interface of TPD and the corresponding lutetium complex. A maximum luminance of 1010 cdxa0m−2 at 16 V from the exciplex was obtained with the highest power efficiency of 0.13 lmxa0W−1 at 9 V and a turn-on voltage as low as 3 V for the device with a (ITO)/TPD(10 nm)/B(50 nm)/BCP(20 nm)/AlQ(40 nm)/Mg0.9Ag0.1(100 nm)/Ag (100 nm) configuration.

Organic light-emitting diodes (LEDs) based on Langmuir-Blodgett films containing rare-earth complexes

Abstract In this paper we report the construction of an organic light-emitting diode (LED) containing a rare-earth molecular complex that was deposited as a Langmuir-Blodgett (LB) film. The complex is a donor-conjugated π-electron system acceptor (D-π-molecular cation coupled to a monovalent anion containing a trivalent rare-earth (Nd 3+ ) cation surrounded by four organic singly charged anionic ligands. Devices were fabricated by LB deposition of multilayer films onto an indium-tin oxide (ITO)-coated glasls substrate on top of which aluminium was evaporated to form the diode structure. Such devices are found to electroluminesce when subjected to a forward bias of a few volts. We present here the electrical and optical characteristics of the device.

Photoelectric response of a bilayer lipid membrane doped with an azo pyridinium compound containing a rare-earth-metal complex

A highly photoactive bilayer lipid membrane (BLM) doped with a new azopyridinium with a large lanthanide complex counterion has been studied. The light intensity of irradiation, the concentration of the azopyridinium compound in the BLM, the concentration of acceptor and the applied voltage are all limiting factors of the photocurrent. Tautomerization of the azopyridinium compound takes place under irradiation. The mechanism for photoelectric effect of the titled BLM system has also been proposed.