Electrochemiluminescence Studies of Phosphorescent Dopant and Host Molecules of Polymer Light-emitting Diodes

Electrochemiluminescence (ECL) from tris(2‐phenylpyridine)irdium [Ir(ppy)₃] was investigated following cross reaction of its anion with oxidized poly(N‐vinyl‐carbazole) (PVK) and its cation with reduced 2‐(4‐biphenylyl)‐5‐(4‐tert‐butyl‐phenyl)‐1,3,4‐oxadiazole (PBD). Both cross reactions show Ir(ppy)₃ emission and the cross reaction of PVK^+·/Ir(ppy)⁻₃ showed the highest ECL intensity. The comparisons of the reaction enthalpy and the energy of Ir(ppy)₃ light emitting shows that reaction between PVK^+· and Ir(ppy)⁻₃ is energy sufficient to populate metal‐to‐ligand charge transfer (MLCT) excited singlet (3.04 eV) of Ir(ppy)₃, while the reaction between Ir(ppy)⁺₃ and PBD^{− ·} is energy efficient to populate MLCT excited triplet (2.4 eV). The ECL result in solution reveals that the energy released from charge transfer between the Ir(ppy)₃ and PVK or PBD is sufficient to produce the excited state of Ir(ppy)₃ in solid polymer light‐emitting diodes (PLEDs) based on PVK:PBD hosts doped by Ir(ppy)₃. These results obtained will provide further insight into charge‐transfer excitation in PLEDs.     

The Preparation of (8‐Hydroxyquinolinato)Bis(2‐Phenylpyridyl)Iridium Complexes and Their Photophysical Properties

Four derivatives of the titled compounds, (8‐hydroxyquinoline)bis(2‐phenylpyridyl)iridium ( IrQ(ppy)₂ ), were prepared. Two of them were confirmed by single crystal X‐ray diffraction analyses, in which solvent molecules were found to be incorporated in the crystal lattices. Their emission spectra display separated dual bands in de‐aerated solutions at about 515 and 645 nm upon excitation. These green and red emissions are attributed to the triplet metal‐to‐ligand charge transfer (³MLCT) and triplet ligand centered (³LC) transitions in Ir(ppy)₂ and IrQ, respectively. It is suggested that such a multiple emission is feasible by nearly orthogonal orientation between the ppy and quinoline ligands in the mixed‐ligand Ir‐compounds which prohibits energy transfer between the two different ligands. The electroluminescence (EL) of these compounds was examined by the fabrication of light‐emitting diodes (LEDs). Unlike the spectra in solutions, their EL spectra displayed only the red emission band. Devices displaying white light can be obtained by mixing the red emission of IrQ(ppy)₂ with a compatible blue emitter (NPB) in separated layers.     

Spin–Orbit Coupling in Phosphorescent Iridium(III) Complexes

We study the excited states of two iridium(III) complexes with potential applications in organic light‐emitting diodes: fac‐tris(2‐phenylpyridyl)iridium(III) [Ir(ppy)₃] and fac‐tris(1‐methyl‐5‐phenyl‐3‐n‐propyl‐[1,2,4]triazolyl)iridium(III) [Ir(ptz)₃]. Herein we report calculations of the excited states of these complexes from time‐dependent density functional theory (TDDFT) with the zeroth‐order regular approximation (ZORA). We show that results from the one‐component formulation of ZORA, with spin–orbit coupling included perturbatively, accurately reproduce both the results of the two‐component calculations and previously published experimental absorption spectra of the complexes. We are able to trace the effects of both scalar relativistic correction and spin–orbit coupling on the low‐energy excitations and radiative lifetimes of these complexes. In particular, we show that there is an indirect relativistic stabilisation of the metal‐to‐ligand charge transfer (MLCT) states. This is important because it means that indirect relativistic effects increase the degree to which SOC can hybridise singlet and triplet states and hence plays an important role in determining the optical properties of these complexes. We find that these two compounds are remarkably similar in these respects, despite Ir(ppy)₃ and Ir(ptz)₃ emitting green and blue light respectively. However, we predict that these two complexes will show marked differences in their magnetic circular dichroism (MCD) spectra.     

Greenish‐yellow‐, yellow‐, and orange‐light‐emitting iridium(III) polypyridyl complexes with poly(ε‐caprolactone)–bipyridine macroligands

A set of novel greenish‐yellow‐, yellow‐, and orange‐light‐emitting polymeric iridium(III) complexes were synthesized with the bridge‐splitting method. The respective dimeric precursor complexes, [Ir(ppy)₂‐μ‐Cl]₂ (ppy = 2‐phenylpyridine) and [Ir(ppy? CHO)₂‐μ‐Cl]₂ [ppy? CHO = 4‐(2‐pyridyl)benzaldehyde], were coordinated to 2,2′‐bipyridine carrying poly(ε‐caprolactone) tails. The resulting emissive polymers were characterized with one‐dimensional (¹H) and two‐dimensional (¹H? ¹H correlation spectroscopy) nuclear magnetic resonance and infrared spectroscopy, gel permeation chromatography, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and the successful coordination of the iridium(III) centers to the 2,2′‐bipyridine macroligand was revealed. The thermal behavior was studied with differential scanning calorimetry and correlated with atomic force microscopy. Furthermore, the quantitative coordination was verified by both the photophysical and electrochemical properties of the mononuclear iridium(III) compounds. The photoluminescence spectra showed strong emissions at 535 and 570 nm. The color shifts depended on the substituents of the cyclometallating ligands. Cyclic voltammetry gave oxidation potentials of 1.23 V and 1.46 V. Upon the excitation of the films at 365 nm, yellow light was observed, and this could allow potential applications in light‐emitting devices. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2765–2776, 2005     

Microwave Assisted Synthesis of a New Triplet Iridium(III) Pyrazine Complex

A new cyclometalated iridium(III) complex Ir(DPP)₃ (DPP=2,3-diphenylpyrazine) was pre-pared by reaction of DPP with iridium trichloride hydrate under microwave irradiation. The structure of the complex was confirmed by elemental analysis, ¹H NMR, and mass spec-troscopy. The UV-Vis absorption and photoluminescent properties of the complex were investigated. The complex shows strong ¹MLCT (singlet metal to ligand charge-transfer) and ³MLCT (triplet metal to ligand charge-transfer) absorption at 382 and 504 nm, respec-tively. The complex also shows strong photoluminescence at 573 nm at room temperature.These results suggest the complex to be a promising phosphorescent material.     

一种新型红色三线态喹喔啉铱(Ⅲ)配合物的合成及发光性质

利用2,3-二苯基喹喔啉和水合三氯化铱(IrCl₃?H₂O)反应, 合成了一种新型喹喔啉铱的配合物[Ir(DPQ)₂(acac)], 通过元素分析, ¹H NMR和HRMS对配合物结构进行了表征, 结果显示得到的是目标化合物. 利用紫外光谱和荧光光谱对配合物的吸收光谱和光致发光光谱进行了研究. 利用该材料作为磷光材料制备了结构为[ITO/NPB(30 nm)/NPB∶7% Ir(DPQ)₂(acac)(25 nm)/PBD (10 nm)/Alq₃ (30 nm)/Mg∶Ag (10∶1)(120 nm)/Ag(10 nm)] 的电致发光器件, 研究了其电致发光光谱. 结果表明, 配合物[Ir(DPQ)₂(acac)]在476和625 nm处存在单重态¹MLCT(金属到配体的电荷跃迁)和三重态³MLCT的吸收峰; 发光光谱结果显示, 在660 nm处有较强的金属配合物三重态的磷光发射; 电致发光光谱显示, 该器件的启动电压是4.25 V, 器件的最大亮度为4910 cd/m², 外量子效率为5.14%, 器件的流明效率为1.12 lm/W, 是一种新型红色磷光材料.     

Understanding Electrogenerated Chemiluminescence Efficiency in Blue‐Shifted Iridium(III)‐Complexes: An Experimental and Theoretical Study

Compared to tris(2‐phenylpyridine)iridium(III) ([Ir(ppy)₃]), iridium(III) complexes containing difluorophenylpyridine (df‐ppy) and/or an ancillary triazolylpyridine ligand [3‐phenyl‐1,2,4‐triazol‐5‐ylpyridinato (ptp) or 1‐benzyl‐1,2,3‐triazol‐4‐ylpyridine (ptb)] exhibit considerable hypsochromic shifts (ca. 25–60 nm), due to the significant stabilising effect of these ligands on the HOMO energy, whilst having relatively little effect on the LUMO. Despite their lower photoluminescence quantum yields compared with [Ir(ppy)₃] and [Ir(df‐ppy)₃], the iridium(III) complexes containing triazolylpyridine ligands gave greater electrogenerated chemiluminescence (ECL) intensities (using tri‐n‐propylamine (TPA) as a co‐reactant), which can in part be ascribed to the more energetically favourable reactions of the oxidised complex (M⁺) with both TPA and its neutral radical oxidation product. The calculated iridium(III) complex LUMO energies were shown to be a good predictor of the corresponding M⁺ LUMO energies, and both HOMO and LUMO levels are related to ECL efficiency. The theoretical and experimental data together show that the best strategy for the design of efficient new blue‐shifted electrochemiluminophores is to aim to stabilise the HOMO, while only moderately stabilising the LUMO, thereby increasing the energy gap but ensuring favourable thermodynamics and kinetics for the ECL reaction. Of the iridium(III) complexes examined, [Ir(df‐ppy)₂(ptb)]⁺ was most attractive as a blue‐emitter for ECL detection, featuring a large hypsochromic shift (λ_max=454 and 484 nm), superior co‐reactant ECL intensity than the archetypal homoleptic green and blue emitters: [Ir(ppy)₃] and [Ir(df‐ppy)₃] (by over 16‐fold and threefold, respectively), and greater solubility in polar solvents.     

Cyclometalated Ir(III) complexes containing N-aryl picolinamide ancillary ligands

The reaction of the cyclometalated chloro-bridged iridium(III) dimer, [(ppy)₂ Ir(μ-Cl)]₂ (ppy - 2-phenyl pyridine) with N-aryl picolinamides (LH, LH-NO₂, LH-CH₃, LH-l, LH-F) resulted in the formation of neutral heteroleptic complexes [Ir(ppy)₂L] (1), [Ir(ppy)₂L-NO₂](2), [Ir(ppy)₂L-CH₃](3), [Ir(ppy)₂L-Cl](4) and [Ir(ppy)₂L-F] (5). These complexes contain a six-coordinate iridium with a 2C, 4N coordination environment. The N-aryl picolinamide ligands are deprotonated during complexation and the resulting amidates bind to iridium in a chelating manner (N, N). Optical spectroscopic studies revealed that the complexes 1-5 exhibited intense π→π^∗ absorptions in the ultraviolet region. In addition low energy transitions due to ¹MLCT, ¹LLCT and ³MLCT are also seen. The emission spectra of 1-5, upon excitation at 450 nm, show a single emission with a λ_max around 513 nm. The lifetimes of this emission are in between 7.4 and 9.6 μs while the quantum yields are quite high and range from 0.2 to 0.5. Based on density functional theory (DFT) calculations on 1 and 3, the three highest occupied orbitals are composed of ligand π orbitals mixed with Ir-d orbitals while the three lowest unoccupied orbitals are mostly π orbitals of the ligands. From the time dependent DFT calculations it is revealed that the lowest energy electronic singlet and triplet excitations are a mixture of MLCT and LLCT.     

Synthesis and characterization of phosphorescent cyclometalated iridium complexes containing 2,5‐diphenylpyridine based ligands

A series of phosphorescent cyclometalated iridium complexes with 2,5‐diphenylpyridine‐based ligands has been synthesized and characterized to investigate the effect of the simple ligand modification on photophysics, thermostability and electrochemistry. The complexes have the general structure (C^∧N)₂Ir(acac), where C^∧N is a monoanionic cyclometalating ligand [e.g. 2,5‐diphenylpyridyl (dppy), 2,5‐di(4‐methoxyphenyl)pyridyl (dmoppy), 2,5‐di(4‐ethoxyphenyl)pyridyl (deoppy) and 2,5‐di(4‐ethylphenyl)pyridyl (deppy)]. The absorption, emission, cyclic voltammetry and thermostability of the complexes were systematically investigated. The (dppy)₂Ir(acac) has been characterized using X‐ray crystallography. Calculation on the electronic ground state of (dppy)₂Ir(acac) was carried out using B3LYP density functional theory. The highest occupied molecular orbital (HOMO) level is a mixture of Ir and ligand orbitals, while the lowest occupied molecular orbital (LUMO) is predominantly dppy ligand‐based. Electrochemical studies showed the oxidation potentials of (dmoppy)₂Ir(acac), (deoppy)₂Ir(acac), (deppy)₂Ir(acac) were smaller than that of (ppy)₂Ir(acac), while the oxidation potential of (dppy)₂Ir(acac) was larger relative to (ppy)₂Ir(acac). The 10% weight reduction temperatures of these complexes were above that of (ppy)₂Ir(acac). All complexes exhibited intense green photoluminescence, which has been attributed to MLCT triplet emission. The maximum emission wavelengths in CH₂Cl₂ at room temperature were in the range 531–544 nm, which is more red‐shifted than that of (ppy)₂Ir(acac). Copyright © 2005 John Wiley & Sons, Ltd.     

Phosphorescent organic light‐emitting diodes using an iridium complex polymer as the solution‐processible host material

We prepared an iridium polymer complex having 2‐phenylpyridine as a η²‐cyclometallated ligand, a new OLED containing a solution‐processible iridium polymer as a host, and a phosphorescent iridium complex, [Ir(piq‐^tBu)₃] as a guest. This is the first example to apply a phosphorescent iridium complex polymer to a host material in a phosphorescent OLED. A phosphine copolymer ligand made from methyl methacrylate (MMA) and 4‐styryldiphenylphosphine can be used as an anchor polymer, which coordinates to luminescent iridium units to form a host metallopolymer easily. The OLED containing the host iridium‐complex polymer film, in which the guest, 2 wt % Ir(piq‐^tBu)₃, was doped, showed red electroluminescence as a result of efficient energy transfer from the iridium polymer host to the iridium guest. The maximum current efficiency of the device was 1.00, suggesting that a soluble iridium complex polymer can be used as a solution‐processible polymer host in EL devices. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4358–4365, 2009     

Luminescent cyclometalated Rh(III), Ir(III), and (DIP)2Ru(II) complexes with carboxylated bipyridyl ligands: synthesis, X-ray molecular structure, and photophysical properties

Luminescent cyclometalated rhodium(III) and iridium(III) complexes of the general formula [M(ppy) 2(N (wedge)N)][PF 6], with N (wedge)N = Hcmbpy = 4-carboxy-4'-methyl-2,2'-bipyridine and M = Rh ( 1), Ir ( 2) and N (wedge)N = H 2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine and M = Rh ( 3), Ir ( 4), were prepared in high yields and fully characterized. The X-ray molecular structure of the monocarboxylic iridium complex [Ir(ppy) 2(Hcmbpy)][PF 6] ( 2) was also determined. The photophysical properties of these compounds were studied and showed that the photoluminescence of rhodium complexes 1 and 3 and iridium complexes 2 and 4 originates from intraligand charge-transfer (ILCT) and metal-to-ligand charge-transfer/ligand-centered MLCT/LC excited states, respectively. For comparison purposes, the mono- and dicarboxylic acid ruthenium complexes [Ru(DIP) 2(Hcmbpy)][Cl] 2 ( 5) and [Ru(DIP) 2(H 2dcbpy)][Cl] 2 ( 6), where DIP = 4,7-diphenyl-1,10-phenanthroline, were also prepared, whose emission is MLCT in nature. Comparison of the photophysical behavior of these rhodium(III), iridium(III), and ruthenium(II) complexes reveals the influence of the carboxylic groups that affect in different ways the ILCT, MLCT, and LC states.     

Synthesis of fac‐Ir(ppy)3 end‐functionalized poly(1,3‐cyclohexadiene): single monomer addition of fac‐Ir(ppy)2(vppy) for well‐controlled polymer synthesis

Synthesis of the polymer whose end is functionalized by fac‐Ir(ppy)₃ (ppy = 2‐phenylpyridyl) was achieved by using (living) anionic polymerization of 1,3‐cyclohexadiene: the reaction of poly(1,3‐cyclohexadienyl)lithium (PCHDLi) with fac‐Ir(ppy)₂(vppy) [vppy = 2‐(4‐vinylphenyl)pyridyl] resulted in nucleophilic attack of the carbanion in PCHDLi on the vinyl group of fac‐Ir(ppy)₂(vppy) selectively. Complexation of the pyridyl ring protected the α‐carbons of fac‐Ir(ppy)₂(vppy) from the reaction of the anionic polymer. The homopolymerization of fac‐Ir(ppy)₂(vppy) did not occur, and only one molecule of fac‐Ir(ppy)₂(vppy) reacted with the carbanion of PCHDLi and was selectively incorporated into an end of poly(1,3‐cyclohexadiene) (PCHD). Thus, the PCHD with fac‐Ir(ppy)₃ end‐group was obtained with a well‐controlled and defined polymer structure and molecular weight. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

New host homopolymers containing pendant triphenylamine derivatives: Synthesis,optical, electrochemical properties and its blend with Ir(ppy)3 for green phosphorescent organic light‐emitting devices

Two vinyl homopolymers poly(N‐(4‐(4‐(4‐vinylbenzyloxy)styryl)phenyl)‐N‐phenylbenzenamine) (PVST ) and poly(4‐vinyltriphenylamine) (PTPA ) containing pendant hole‐transporting triphenylamine and 4‐oxystyryltriphenylamine groups, respectively, were synthesized by radical polymerization and employed as hosts for tris(2‐phenylpyridine) iridium [Ir(ppy)₃] phosphor. Structural influences of the hole‐transporting groups upon optoelectronic properties were investigated by photophysical, electrochemical, and electroluminescent methods. The polymers were readily soluble in common organic solvents and their weight‐average molecular weights (M_w) were 5.68 × 10⁴ and 1.90 × 10⁴, respectively. The emission spectra (both photoluminescence, PL and electroluminescent, EL) of the blends [PTPA with 4 wt % Ir(ppy)₃] showed dominant green emission (517 nm) attributed to Ir(ppy)₃ due to efficient energy transfer from PTPA to Ir(ppy)₃. The HOMO levels of PVST and PTPA, estimated from onset oxidation potentials in their cyclic voltammograms, were ?5.14 and ?5.36 eV, which are much higher than ?5.8 eV of the conventional poly(9‐vinylcarbazole) (PVK) host owing to high hole‐affinity of the triphenylamine groups. The optoelectronic performances of phosphorescent EL devices, using PVST and PTPA as hosts and Ir(ppy)₃ as dopant (indium tin oxide, ITO/poly(3,4‐ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS)/PVST or PTPA:Ir(ppy)₃(4 wt %):PBD(40 wt %)/BCP/Ca/Al), were investigated. The maximum luminance and luminance efficiency of the PTPA device were 9220 cd/m² and 6.1 cd/A, respectively, which were significantly improved relative to those of PVK and PVST. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7960–7971, 2008     

Photophysical Properties of Heteroleptic Iridium Complexes Containing Carbazole‐Functionalized β‐Diketonates

Twelve iridium complexes with general formula of Ir(C^N)₂(LX) [C^N represents the cyclometalated ligand, i.e. 2‐(2,4‐difluorophenyl) pyridine (dfppy), 2‐phenylpyridine (ppy), dibenzo{f, h}quinoxaline (DBQ); LX stands for β‐diketonate, i.e. acetyl acetonate (acac), 1‐(carbazol‐9‐yl)‐5,5‐dimethylhexane‐2,4‐diketonate (CBDK), 1‐(carbazol‐9‐yl)‐5,5,6,6,7,7,7‐heptafluoroheptane‐2,4‐diketonate (CHFDK), 1‐(N‐ethyl‐carbazol‐3‐yl)‐4,4,5,5,6,6,6‐heptafluorohexane‐1,3‐diketonate (ECHFDK)] are synthesized, characterized and their photophysical properties are systemically studied. In addition, crystals of Ir(DBQ)₂(CHFDK) and Ir(DBQ)₂(acac) are obtained and characterized by single crystal X‐ray diffraction. The choice of these iridium complexes provides an opportunity for tracing the effect of the triplet energy level of ancillary ligands on the photophysical and electrochemical behaviors. Data show that if the triplet energy level of the β‐diketonate is higher than that of the Ir(C^N)₂ fragment and there is no superposition on the state density map, strong ³LC or ³MLCT‐based phosphorescence can be obtained. Alternatively, if the state density map of the two parts are in superposition, the ³LC or ³MLCT‐based transition will be quenched at room temperature. Density functional theory calculations show that these complexes can be divided into two categories. The lowest excited state is mainly determined by C^N but not β‐diketonate when the difference between the triplet energy levels of the two parts is large. However, when this difference is very small, the lowest excited state will be determined by both sides. This provides a satisfactory explanation for the experimental observations.     

Robust Tris‐Cyclometalated Iridium(III) Phosphors with Ligands for Effective Charge Carrier Injection/Transport: Synthesis,Redox, Photophysical,and Electrophosphorescent Behavior

With the target to design and develop new functionalized green triplet light emitters that possess distinctive electronic properties for robust and highly efficient phosphorescent organic light‐emitting diodes (PHOLEDs), a series of bluish–green to yellow–green phosphorescent tris‐cyclometalated homoleptic iridium(III) complexes [Ir(ppy‐X)₃] (X=SiPh₃, GePh₃, NPh₂, POPh₂, OPh, SPh, SO₂Ph, Hppy=2‐phenylpyridine) have been synthesized and fully characterized by spectroscopic, redox, and photophysical methods. By chemically manipulating the lowest triplet‐state character of Ir(ppy)₃ with some functional main‐group 14–16 moieties on the phenyl ring of ppy, a new family of metallophosphors with high‐emission quantum yields, short triplet‐state lifetimes, and good hole‐injection/hole‐transporting or electron‐injection/electron‐transporting properties can be obtained. Remarkably, all of these Ir^III complexes show outstanding electrophosphorescent performance in multilayer doped devices that surpass that of the state‐of‐the‐art green‐emitting dopant Ir(ppy)₃. The devices described herein can reach the maximum external quantum efficiency (η_ext) of 12.3 %, luminance efficiency (η_L) of 50.8 cd A^?1, power efficiency (η_p) of 36.9 Lm W^?1 for [Ir(ppy‐SiPh₃)₃], 13.9 %, 60.8 cd A^?1, 49.1 Lm W^?1 for [Ir(ppy‐NPh₂)₃], and 10.1 %, 37.6 cd A^?1, 26.1 Lm W^?1 for [Ir(ppy‐SO₂Ph)₃]. These results provide a completely new and effective strategy for carrier injection into the electrophosphor to afford high‐performance PHOLEDs suitable for various display applications.     

一种基于咔唑的新型磷光主体材料的合成及光电性能

设计并合成了一种基于咔唑的新型的磷光主体材料, 即9-(6-(9-咔唑基)己基)咔唑(hCP), 对其结构及性能进行了表征. 研究结果表明: hCP分子中两个咔唑与烷基链是非共平面的, 由于长烷基链的缠绕, 因而具有较高的三线态能级(3.01 eV)和较高的玻璃化温度(93℃); 以hCP为主体材料, 与绿光磷光染料三(2-苯基吡啶)合铱(Ir(ppy)₃)掺杂作为发光层, 制备了磷光电致发光器件, 其器件的最大电流效率为15.1 cd·A^-1, 相对于4,4'-N,N'-二咔唑基联苯(CBP)为主体材料的参考器件, 显著提高了34.8%.     

Photodegradation‐induced photoluminescence behaviors of π‐conjugated polymers upon the doping of organometallic triplet emitters

The different effects on the photodegradation‐induced photoluminescence (PL) of π‐conjugated polymeric thin films upon the doping of Ir(III) containing triplet emitters in ambient conditions at room temperature were investigated. In this study, we prepared spin‐coated thin films using three different polymer matrices including poly(9‐vinylcarbazole) (PVK), poly[9,9‐bis(2‐ethylhexyl)fluorene‐2,7‐diyl] (PF2/6), and poly[2‐(5′‐cyano‐5′‐methyl‐hexyloxy)‐1,4‐phenylene] (CNPPP) derivatives doped with Ir(III) containing triplet emitters: Ir(III) bis[(4,6‐fluorophenyl)‐pyridinato‐N,C²′] picolinate (FIrpic), or Ir(III)fac‐tris(2‐phenylpyridine) (Ir(ppy)₃), or Ir(III)bis(2‐(2′‐benzothienyl) pyridinato‐N‐acetylacetonate) (Ir(btp)₂acac). Using the doped films, and their neat films, on quartz substrates, the UV‐Visible absorption (UV‐Vis) and PL spectra were recorded under continuous illumination with the excitation wavelengths at the absorption maxima of the corresponding matrix polymers. The dopant effects on the photodegradation‐induced PL were extracted from the kinetic data obtained from the doped films by subtracting the mutual degradation kinetics of their corresponding neat films. The obtained dopant effects show a strong correlation between the photo‐induced PL degradation and the exciton migration behaviors. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2395–2403, 2008     

Cascade hole transport in efficient green phosphorescent light‐emitting devices achieved by layer‐by‐layer solution deposition using photocrosslinkable‐conjugated polymers containing oxetane side‐chain moieties

A hole‐injection/transport bilayer structure on an indium tin oxide (ITO) layer was fabricated using two photocrosslinkable polymers with different molecular energy levels. Two photoreactive polymers were synthesized using 2,7‐(or 3,6‐)‐dibromo‐9‐(6‐((3‐methyloxetan‐3‐yl)methoxy)hexyl)‐9H‐carbazole) and 2,4‐dimethyl‐N,N‐bis(4‐ (4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)phenyl)aniline via a Suzuki coupling reaction. When the oxetane groups were photopolymerized in the presence of a cationic photoinitiator, the photocured film showed good solvent resistance and compatibility with a poly(N‐vinylcarbazole) (PVK)‐based emitting layer. Without the use of a conventional hole injection layer (HIL) of poly(3,4‐ethylenedioxythiophene)/(polystyrenesulfonate) (PEDOT:PSS), the resulting green light‐emitting device bearing PVK: 5‐4‐tert‐butylphenyl‐1,3,4‐oxadiazole (PBD):Ir(Cz‐ppy)3 exhibited a maximum external quantum efficiency of 9.69%; this corresponds to a luminous efficiency of 29.57 cd/A for the device K‐4 configuration ITO/POx‐I/POx‐II/PVK:PBD:Ir(Cz‐ppy)3/triazole/Alq3/LiF/Al. These values are much higher than those of PLEDs using conventional PEDOT:PSS as a single HIL. The significant improvement in device efficiency is the result of suppression of the hole injection/transport properties through double‐layered photocrosslinked‐conjugated polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

New preparative procedure for photoluminescent metallopolymers having a biphenyl‐2,2′‐diyl iridium(III) unit bound to a phosphine copolymer ligand

We first prepared polymer‐bound photoluminescent iridium complexes bearing a cyclometalated 2,2′‐biphenylene ligand via an easy procedure in which the metallopolymer was synthesized by the reaction of a metal precursor with a polymer ligand. The iridium compound, [Ir(cod)(biph)Cl]₂ (where cod and biph are 1,5‐cyclooctadiene and biphenyl‐2,2′‐diyl, respectively), was used as the iridium material, and a copolymer built by the radical copolymerization of 4‐styryldiphenylphosphine and methyl methacrylate was employed as the polymer ligand. The obtained metallopolymers were highly crosslinked by iridium atoms forming P? Ir? P bonds. The content of the iridium was experimentally clarified to be in the range of 0.06–0.6 mmol/g of the polymer. Photoluminescence of the iridium polymer in the solid state was observed at 597 nm when the polymer was irradiated at 350 nm. As the Ir content in the copolymer increased to 0.2 mmol/g, the intensity of the luminescence also increased, but more iridium content decreased the intensity. Furthermore, the intensity of the photoluminescence in these photoluminescent polymers depended on the molecular weight of the copolymer ligands. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4204–4213, 2006     

新型黄色磷光吡嗪铱(Ⅲ)配合物的合成及发光性质

利用2,3-二苯基吡嗪与水合三氯化铱反应合成了一种新型吡嗪铱的配合物[Ir(dphp)₂(acac)],通过元素分析,¹HNMR和MS对配合物结构进行了表征,并研究了配合物的吸收光谱和光致发光光谱.利用该材料作为磷光染料制备了结构为[ITO/NPB(30nm)/NPB;8%[Ir(dphp)₂(acac)](25nm)/PBD(10nm)/Alq₃(30nm)/Mg;Ag(质量比9;1)(130nm)的电致发光器件,研究了其电致发光光谱.结果表明,该配合物在393和528nm处存在单重态¹MLCT(金属到配体的电荷跃迁)和三重态³MLCT的吸收峰;荧光光谱结果显示,在588nm处有较强的金属配合物三重态的磷光发射;电致发光光谱显示,该器件的启动电压是3.25V,器件的最大亮度为11478cd/m²,外量子效率为13.85%,器件的流明效率为15.54lm/W,是一种新型的高效率黄色磷光材料.