Red-light-emitting iridium complexes with hole-transporting 9-arylcarbazole moieties for electrophosphorescence efficiency/color purity trade-off optimizationE

The synthesis, structures, photophysics, electrochemistry and electrophosphorescent properties of new red phosphorescent cyclometalated iridium(III) isoquinoline complexes, bearing 9-arylcarbazolyl chromophores, are reported. The functional properties of these red phosphors correlate well with the results of density functional theory calculations

Red-Light-Emitting Iridium Complexes with Hole-Transporting 9-Arylcarbazole Moieties for Electrophosphorescence Efficiency/ Color Purity Trade-off Optimization

The synthesis, structures, photophysics, electrochemistry and electrophosphorescent properties of new red phosphorescent cyclometalated iridium(III) isoquinoline complexes, bearing 9-arylcarbazolyl chromophores, are reported. The functional properties of these red phosphors correlate well with the results of density functional theory calculations. The highest occupied molecular orbital levels of these complexes are raised by the integration of a carbazole unit to the iridium isoquinoline core so that the hole-transporting ability is improved in the resulting complexes relative to those with I-phenylisoquinoline ligands. All of the complexes are highly thermally stable and emit an intense red light at room temperature with relatively short lifetimes that are beneficial for highly efficient organic light-emitting diodes (OLEDs).

Diarylmethylene-bridged 4,4 '-(bis(9-carbazolyl))biphenyl: morphological stable host material for highly efficient electrophosphorescence

novel compound (BCBP) based on the modification of a well-known host material 4,4'-(bis(9-carbazolyl))biphenyl (CBP) through arylmethylene bridge linkage was synthesized, and fully characterized. Its thermal, electrochemical, electronic absorption and photoluminescent properties were studied. A high glass transition temperature (T-g) of 173 degrees C is observed for BCBP due to the introduction of the bridged structure, remarkably contrasting with a low T-g of 62 degrees C for CBP. Furthermore, the bridged structure enhances the conjugation and raises the HOMO energy, thus facilitating hole-injection and leading to a low turn-on voltage in an electroluminescent device. With the device structure of ITO/MoO3/NPB/Ir complex: BCBP/BCP/Alq(3)/LiF/Al, maximum power efficiencies of 41.3 lm/W and 6.3 lm/W for green- and blue-emitting OLED were achieved, respectively.

Blue organic light-emitting diodes based on an oxadiazole-containing organic molecule exhibiting excited state intramolecular proton transfer

A blue organic light-emitting device based on an emissive layer of 2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole (HOXD), which exhibits excited state intramolecular proton transfer (ESIPT), was presented. The device had a luminance efficiency of 0.8 cd/A and a maximum brightness of 870 cd/m(2). Our studies indicate that some EL may originate from the triplet excitation state of the enol form of HOXD.

Blue organic light-emitting devices with an oxadiazole-containing emitting layer exhibiting excited state intramolecular proton transfer

We report a blue organic light-emitting device having an emissive layer of 2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole (HOXD), that exhibits excited state intramolecular proton transfer (ESIPT). The device had a luminance efficiency of 0.8 cd/A and a maximum brightness of 870 cd/m(2). Electroluminescence spectra revealed a dominating peak at 450 nm and two additional peaks at 480 and 515 nm with a full width at half maximum of 50 nm. Our studies indicate that some EL may originate from the triplet excitation state of the enol form of HOXD.

Synthesis and Properties of Carbazole Main Chain Copolymers with Oxadiazole Pendant toward Bipolar Polymer Host: Tuning the HOMO/LUMO Level and Triplet Energy

Three new carbazole copolymers, poly(9-(2,5-diarene-[1,3,4]oxadiazole)-carbazole-alt-9-(2-ethylhexyl)-carbazole-3,6-diyl)s (P1), poly(9-(2,5-diarene-[1,3,4]oxadiazole)-2, 7-carbazole-alt-9-(2-ethylhexyl)-3, 6-carbazole-diyl)s (P2), and poly(9-(2,5-diarene-[1,3,4]oxadiazole)-carbazole-alt-9-(2-ethylhexyl)-carbazole-2,7-diyl)s (P3), were synthesized by the Suzuki coupling reaction

Novel Oligo-9,9 '-spirobifluorenes through ortho-Linkage as Full Hydrocarbon Host for Highly Efficient Phosphorescent OLEDs

4-Bromo-9,9'-spirobifluorene is facilely synthesized, and from this precursor, two ortho-linked oligo-9,9'-spirobifluorenes, 44BSF and 24TSF, are constructed. Devices with 24TSF as the full-hydrocarbon host material and Ir(ppy)(3) or (ppq)(2)Ir(acac) as the triplet emitter show maximum external quantum efficiencies of 12.6 and 10.5% for green and red electrophosphorescence, respectively.

A Fully Diarylmethylene-Bridged Triphenylamine Derivative as Novel Host for Highly Efficient Green Phosphorescent OLEDs

A fully diarylmethylene-bridged triphenylamine derivative is efficiently synthesized. It has an almost planar triphenylamine (TPA) skeleton and exhibits excellent thermal and morphological stability. Devices with the novel TPA derivative as host material and Ir(ppy)(3) as triplet emitter show a maximum current efficiency of 83.5 cd/A and a maximum power efficiency of 71.4 Im/W for green electrophosphorescence.

Tuning the saturated red emission: synthesis, electrochemistry and photophysics of 2-arylquinoline based iridium(III) complexes and their application in OLEDs

A series of novel iridium(III) complexes with two 2-arylquinoline derivatives as cyclometalated ligands and one monoanionic ligand, such as acetylacetonate (acac), N,N'-diethyldithiocarbamate (Et(2)dtc) and O,O'-diethyldithiophosphate (Et(2)dtp), as ancillary ligands have been synthesized and structurally characterized by H-1 NMR, MS and elemental analysis (EA). The cyclic voltammetry, absorption, emission and electroluminescence properties of these complexes were systematically investigated. Through extending pi-conjugation, introducing electron-donating groups in the ligand frame, or changing the ancillary ligands, the HOMO energy levels of the iridium(III) complexes can be tuned, while their LUMO levels remain little affected; in consequence, the emission wavelengths of the iridium(III) complexes can be tuned in the range 606-653 nm. The highly efficient organic light-emitting diodes (OLEDs) with saturated red emission have been demonstrated. A maximum current efficiency of 10.79 cd A(-1), at a current density of 0.74 mA cm(-2), with an emission wavelength of 616 nm and Commisioon Internationale de L'Eclairage (CIE) coordinates of (0.65, 0.35), which are very close to the National Television System Comittee (NSTC) standard red emission, have been achieved when using complex (DPQ)(2)Ir(acac) as a phosphor dopant.

Highly efficient phosphorescent bis-cyclometalated iridium complexes based on quinoline ligands

The synthesis and electrochemical and photophysical study of a series of bis-cyclometalated iridium(III) complexes based on quinoline ligands have been carried out. These complexes are found to emit red-orange to deep red phosphorescence with high quantum yield and short lifetime. The red organic light-emitting diodes (OLEDs) with the external quantum efficiency up to 11.3% were demonstrated. Slow decay of efficiency with increasing current density was observed. These indicate that quinoline-based iridium complexes are promising candidates for efficient red emitters.

A Deep-Blue Electroluminescent Device Based on a Coumarin Derivative

The design and synthesis is reported of 7-(9H-carbazol-9-yl)-4-methylcoumarin (Cz-Cm), comprising a carbazole donor moiety and a 4-methylcoumarin acceptor unit, for use in a blue organic light-emitting diode. A detailed solid state, theoretical and spectroscopic study was performed to understand the structure-property relationships. The material exhibits deep-blue emission and high photoluminescence quantum yield both in solution and in a doped matrix. A deep-blue electroluminescence emission at 430nm, a maximum brightness of 292cdm(-2) and an external quantum efficiency of 0.4% was achieved with a device configured as follows: ITO/NPD (30nm)/TCTA (20nm)/CzSi(10nm)/10wt% Cz-Cm:DPEPO (10nm)/TPBI (30nm)/LiF (1nm)/Al ITO=indium tin oxide, NPD=N,N-di(1-naphthyl)-N,N-diphenyl-(1,1-biphenyl)-4,4-diamine, TCTA=tris(4-carbazoyl-9-ylphenyl)amine, CzSi=9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, DPEPO=bis2-(diphenylphosphino)phenyl]ether oxide, TPBI=1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene].

Electroluminescence of hole block material caused by electron accumulation and hole penetration

In this study, we investigated the electroluminescence (EL) mechanisms and processes of hole block material in the multilayer devices with Eu(TTA)(3)phen (TTA = thenoyltrifluoroacetone, phen = 1,10-phenanthroline) doped CBP (4,4'-N,N'-dicarbazolebiphenyl) as the light-emitting layer (EML). First, the hole block ability of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) was experimentally confirmed by comparing the EL spectra. With increasing hole injection, BCP emission emerges and increases gradually due to the increasing hole penetration from EML into the hole block layer (HBL).

Effect of secondary ligands' size on energy transfer and electroluminescent efficiencies for a series of europium(III) complexes, a density functional theory study

In this paper, a quantum chemistry method was used to investigate the effect of different sizes of substituted phenanthrolines on absorption, energy transfer, and the electroluminescent performance of a series of Eu(TTA)(3)L (L = [1,10] phenanthroline (Phen), Pyrazino[2,3-f][1,10]phenanthroline (PyPhen), 2-methylprrazino[2,3-f][1,10] phenanthroline(MPP), dipyrido[3,2-a:2',3'-c]phenazine(DPPz), 11-methyldipyrido[3,2-a:2',3'c]phenazine(MDPz), 11.12-dimethyldipyrido[3,2-a:2',3'-c]phenazine(DDPz), and benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (BDPz)) complexes. Absorption spectra calculations show that different sizes of secondary ligands have different effects on transition characters, intensities, and absorption peak positions.