Red Phosphorescent Iridium Complex Research Articles

Manipulating Förster and Dexter interactions between a thermally activated delayed fluorescence host and a phosphorescent dopant for highly efficient solution-processed red and white OLEDs

A blue TADF host with and without steric hindrances was utilized to manipulate Fӧrster and Dexter interactions with a red phosphorescent iridium complex, realizing the state-of-the-art PhOLEDs with a sufficiently high EQE of 22.2%.

High color rendering white organic light-emitting diodes fabricated using a broad-bandwidth red phosphorescent emitter for lighting applications

High color rendering white organic light-emitting devices (WOLEDs) were developed using a broad-bandwidth red phosphorescent iridium complex, bis[2-(1-naphthyl)benzothiazolato-N,C2′]iridium(III) acetylacetonate [Ir(absn)2(acac)]. The red phosphorescent emitter Ir(absn)2(acac) was used to fabricate blue–red and blue–green–red WOLEDs by combining blue-emitting bis[2-(4,6-difluorophenyl)pyridinato-N,C2′]iridium(III) picolinate (FIrpic) and green-emitting tris-fac-(2-cyclohexenylpyridine) iridium (III) [Ir(chpy)3] in multiple-emissive layers. Mixed host emissive layers were employed using a hole-transport-type host 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA) and an electron-transport-type host 2,6-bis[3-(carbazol-9-yl)phenyl]pyridine (DCzPPy) for efficient charge carrier injection. Di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane (TAPC) and 1,3-bis(3,5-dipyrid-3-yl-phenyl)benzene (BmPyPB) were used as the hole and electron transporting layers, respectively. The effects of the emissive layer thickness and the doping ratios of different color dopants on WOLED performances were investigated. The WOLED based on ITO/TAPC/TCTA:FIrpic (10%):Ir(absn)2(acac) (4%)/TCTA:Ir(chpy)3 (9%, 6nm)/DCzPPy:FIrpic (13%):Ir(absn)2(acac) (4%)/BmPyPB/LiF/Al exhibited an external quantum efficiency of 10.7%, a power efficiency of 23.0lm/W, a very high color rendering index (CRI) of 88.1, and a correlated color temperature (CCT) of 2629K at 1000cd/m2.

A carbazole-functionalized Ir complex used in efficient single-layer electrophosphorescent devices

The fabrication of electroluminescent devices that combine high device performance with simple device configuration remains an attractive challenge for their low costs and simple fabrication process. In this paper, a novel red phosphorescent iridium complex containing a carbazole-functionalized β-diketonate ligand, bis(1-phenylisoquinolinato-C2,N) iridium 1-(carbazol-9-yl)-5,5-dimethylhexane-2,4-diketonate (Ir(piq)2(CBDK)), is designed, synthesized, and characterized. The electrophosphorescence of Ir(piq)2(CBDK) as an emitter in organic light-emitting diodes was examined and compared with that of Ir(piq)2(acac) (acac=acetylacetonate) without carbazolyl group. A series of single-layer devices containing different concentration gradients of Ir(piq)2(CBDK) as an emitting and hole-transporting material and 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene as an electron-transporting material were constructed. A maximum current efficiency of 9.9cdA−1 and power efficiency of 7.8lmW−1 were obtained, which is one of the best performances obtained for a single-layer device containing one material as a host.

Efficient red phosphorescent iridium complexes for organic light-emitting diodes based on 5-benzoyl-2-phenylpyridine ligands with fluorine and methyl moieties

Red phosphorescent emitters for OLEDs were synthesized using Ir(III) complexes based on 5-benzoyl-2-phenylpyridine ligands with fluorine and methyl substitution. Their electroluminescence, when doped in the emitting layers of multilayer OLEDs, was sensitive to their structural features. In particular, a highly efficient orange-red OLED showed a maximum luminance of 18,740cd/m2 at 11V, with a luminous efficiency of 25.9cd/A, power efficiency of 8.74lm/W, external quantum efficiency of 9.25% at 20mA/cm2, and CIEx,y coordinates of (0.53, 0.47) at 8.0V, respectively. A red OLED with CIEx,y coordinates of (0.66, 0.34) at 8.0V exhibited a luminous efficiency, power efficiency and external quantum efficiency of 5.98cd/A, 2.06lm/W and 5.77% at 20mA/cm2, respectively.

Synthesis and Electrochemical Study of the Ir(III) Complexes Containing the Diphenyl-quinoline, -Quinoxaline and Pyrazolonate Ligands

Ir(dpq/dpqx)2(przl-R) complexes were prepared and their electrochemical properties were investigated, where dpq, dpqx and przl-R represent 2,3-diphenylquinoline, 2,3-diphenylquinoxaline and N-phenyl-R-pyrazolonate derivatives, respectively. The iridium complexes containing dpq and dpqx as main ligands were reported to show red phosphorescence, and involvement of a pyrazolonate ancillaryligand in the iridium complexes ledto highluminous efficiency for organic light-emitting diodes. In this study, we synthesized red phosphorescent iridium complexes containing a new pyrazolonate ancillary ligand and investigated the HOMOs, LUMOs and resulting electrochemical gaps of Ir(dpq/dpqx)2(przl-R) bycyclic voltammetry.Theemission wavelengths of the complexes at600 -640 nm were consistent with the gaps of 1.95 - 2.03 eV measured from reduction and oxidation potentials of the complexes.

Phosphorescent Polymer Light-Emitting Devices Doped with Red Iridium (III) Bis(2-phenyl-Isoquinoine)(2-acetyl-cyclohexane) Complex

Devices with a configuration of ITO/PEDOT/Ir-PIQCH (10 wt%) in Polymer/BAlq (30 nm)/Alq3(20 nm)/LiF (1 nm)/Al (120 nm) were fabricated. In the emitting layer, three different polymers, poly(N-(2-ethyhexyl)-3,6-dibromocarbazole-alt-aniline) (P(3,6-EHCZ-alt-Al)) ( 1 ), poly(bis[6-bromo-N-(2-ethylhexyl)-carbazole-3-yl-alt-aniline] (P(Bis-EHCZ-alt-Al)) ( 2 ) and poly(N-(2-ethyhexyl)-2,7-dibromocarbazole-alt-aniline) (P(2,7-EHCZ-alt-Al)) ( 3 ) were used as a host material, respectively, and new cyclometalated red phosphorescent iridium complex with phenyl-isoquinoline and 2-acetyl-cyclohexanone ligands (Ir-PIQCH) was employed as a guest material. Surface morphology of thin emitting films fabricated by spin-coating from the dilute solution was studied by using 3D optical analyzer. The average roughness of the surface was measured in the range of 1-2 nm to show the films uniformly formed. From the electroluminescent measurement, a red electrophosphorescence was observed with emission peak at approximately 620 nm, 624 nm or 632 nm for Ir-PIQCH doped P(3,6-EHCZ-alt-Al) ( 1 ), Ir-PIQCH doped P(Bis-EHCZ-alt-Al) ( 2 ) or Ir-PIQCH doped P(2,7-EHCZ-alt-Al) ( 3 ) device.

Single‐Molecule Electroluminescence of a Phosphorescent Organometallic Complex

Lighting one by one: The electroluminescence (EL) from single molecules of a red phosphorescent iridium complex dispersed in a hole-transporting polymer matrix is studied. The single-molecule EL dynamics is determined by local structural inhomogeneities in the matrix polymer [picture: see text].

Efficient white polymer-light-emitting-diodes based on polyfluorene end-capped with yellowish-green fluorescent dye and blended with a red phosphorescent iridium complex

A novel series of blue and yellowish-green light-emitting single polymers were prepared by end-capping of low contents of 4-bromo-7H-benzo [de]naphtha[2′,3′:4,5]imidazo[2,1-a]isoquinolin-7-one (M1) into polyfluorene. Electroluminescence (EL) spectra of these polymers exhibit blue emission (λ max = 430/460 nm) from the fluorene segments and yellowish-green emission (λ max = 510/530 nm) from the M1 units. For the polymer (PFNAP-0.06) with the M1 unit content of 0.06 mol-%, its EL spectrum shows balanced intensities of blue emission and yellowish-green emission with Commission Internationale de l'Eclairage (CIE) coordinates of (0.25, 0.34). The maximum brightness of the device prepared from the polymer (PFNAP-0.06) is 6704 cd/m 2 at 10 V with a structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) [PEDOT:PSS]/PVK/emission layer/Ca/Ag. A new white polymer-light-emitting-diode (WPLED) can be developed from the single polymer (PFNAP-0.06) system blended with a red phosphorescent iridium complex [Bis(2-[2′-benzothienyl)-pyridinato-N,C 3′] iridium (acetylacetonate) (BtpIr)]. We were able to obtain a white-light-emission device by adjusting the molar ratio of BtpIr to PFNAP-0.06 with a structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) [PEDOT:PSS]/PVK/emission layer/Ca/Ag. The brightness in such a device configuration is 4030 cd/m 2 at 9 V with CIE coordinates of (0.32, 0.34).

Red Phosphorescent Iridium Complexes having a Bulky Ancillary Ligand for Solution-processed Organic Light Emitting Diodes

Red Phosphorescent Iridium Complexes having a Bulky Ancillary Ligand for Solution-processed Organic Light Emitting Diodes

Synthesis of novel light-emitting polymers and application in diodes with red phosphorescent cyclometalated iridium complex

Novel carbazole- and triarylamine-containing polymers, poly[N-(2-ethylhexyl)carbazole-alt-aniline] (PECA), poly[N-(2-ethylhexyloxy-phenyl)carbazole-alt-aniline] (PEPCA), poly[N-(2-ethylhexyl) carbazole-alt-N-(4-aminophenyl)carbazole] (PECAC) and poly[N-(2-ethylhexyloxy-phenyl)carbazole-alt-N-(4-aminophenyl)carbazole] (PEPCAC) showed good physical, optical, and electronic properties. Study on electrochemical properties of these polymers revealed that the band gap and HOMO energy were 2.91 and −5.19eV for PECA, 3.14 and −5.10eV for PEPCA, 2.97 and −5.01eV for PECAC, and 3.25 and −5.17eV for PEPCAC. Results proved that four polymers could be used as hole-transporting and host-matrix materials for phosphorescent PLEDs. Electrophosphorescent devices were fabricated by using a red phosphorescent iridium complex (IR-PIQCH) as a guest and four polymers as hosts, and the device performance was evaluated in terms of polymer structure, EL emission spectrum, luminance, driving voltage, and color coordinate.

Red Phosphorescent Iridium Complex Containing Carbazole‐Functionalized β‐Diketonate for Highly Efficient Nondoped Organic Light‐Emitting Diodes

AbstractA novel red phosphorescent iridium complex containing a carbazole‐functionalized β‐diketonate, Ir(DBQ)2(CBDK) (bis(dibenzo[f,h]quinoxalinato‐N,C2) iridium (1‐(carbazol‐9‐yl)‐5,5‐dimethylhexane‐2,4‐diketonate)) is designed, synthesized, and characterized. The electrophosphorescence properties of a nondoped device using the title complex as an emitter with a device configuration of indium tin oxide (ITO)/N,N′‐diphenyl‐N,N′‐bis(1‐naphthyl)‐1,1′‐diphenyl‐4,4′‐diamine (NPB; 20 nm)/iridium complex (20 nm)/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP; 5 nm)/tris(8‐hydroxyquinoline) (AlQ; 30 nm)/Mg0.9Ag0.1 (200 nm)/Ag (80 nm) are examined. The results show that the nondoped device achieves a maximum lumen efficiency as high as 3.49 lm W–1. To understand this excellent result observed, two reference complexes Ir(DBQ)2(acac), where acac is the acetyl acetonate anion, and Ir(DBQ)2(FBDK), [bis(dibenzo[f,h]quinoxalinato‐N,C2) iridium (1‐(9‐methyl‐fluoren‐9‐yl)‐6,6‐dimethylheptane‐3,5‐diketonate)], have also been synthesized, and as emitters they were examined under the same device configuration. The maximum lumen efficiency of the former compound is found to be 0.26 lm W–1 while that for the latter is 0.37 lm W–1, suggesting that the excellent performance of Ir(DBQ)2(CBDK) can be attributed mainly to an improved hole‐transporting property that benefits the exciton transport. In addition, a bulky diketonate group separates the emitter centers from each other, which is also important for organic light‐emitting diodes.

Triplet Energy Back Transfer in Conjugated Polymers with Pendant Phosphorescent Iridium Complexes

The nature of Dexter triplet energy transfer between bonded systems of a red phosphorescent iridium complex 13 and a conjugated polymer, polyfluorene, has been investigated in electrophosphorescent organic light-emitting diodes. Red-emitting phosphorescent iridium complexes based on the [Ir(btp)(2)(acac)] fragment (where btp is 2-(2'-benzo[b]thienyl)pyridinato and acac is acetylacetonate) have been attached either directly (spacerless) or through a -(CH(2))(8)- chain (octamethylene-tethered) at the 9-position of a 9-octylfluorene host. The resulting dibromo-functionalized spacerless (8) or octamethylene-tethered (12) fluorene monomers were chain extended by Suzuki polycondensations using the bis(boronate)-terminated fluorene macromonomers 16 in the presence of end-capping chlorobenzene solvent to produce the statistical spacerless (17) and octamethylene-tethered (18) copolymers containing an even dispersion of the pendant phosphorescent fragments. The spacerless monomer 12 adopts a face-to-face conformation with a separation of only 3.6 A between the iridium complex and fluorenyl group, as shown by X-ray analysis of a single crystal, and this facilitates intramolecular triplet energy transfer in the spacerless copolymers 17. The photo- and electroluminescence efficiencies of the octamethylene-tethered copolymers 18 are double those of the spacerless copolymers 17, and this is consistent with suppression of the back transfer of triplets from the red phosphorescent iridium complex to the polyfluorene backbone in 18. The incorporation of a -(CH(2))(8)- chain between the polymer host and phosphorescent guest is thus an important design principle for achieving higher efficiencies in those electrophosphorescent organic light-emitting diodes for which the triplet energy levels of the host and guest are similar.

Synthesis and Electroluminescent Properties of Novel Emissive Iridium Complex with Phenyl-isoquinoline Ligand

ABSTRACT Novel red phosphorescent iridium complex with two phenyl-isoquinoline ligands and one 2-acetyl-cyclopentanone ligand (IR-PIQCP) was designed and synthesized. The electroluminescent (EL) characteristics of IR-PIQCP were evaluated in the EL device. The three kinds of EL devices were fabricated by the vacuum deposition method, and the layer-structures of the devices were ITO/NPD/IR-PIQCP (5%), IR-PIQCP (10%) or IR-BTPAC (10%) in CBP/Balq/Alq/LiF/Al. Emission characteristics of the IR-PIQCP (5%) and IR-PIQCP (10%) devices were about 570 cd/m2 and 550 cd/m2 at 11 mA/cm2 at the same current density respectively. The EL spectra of the IR-PIQCP (5%) and IR-PIQCP (10%) devices were detected at about 627 nm and 629 nm as the maximum peak with red phosphorescence.

Development of novel red phosphorescent iridium complex with phenyl-isoquinoline ligand for organic electroluminescent device

Abstract Novel red phosphorescent compound (IR-PIQC-1), iridium complex with two phenyl-isoquinoline ligands and one 2-acetyl-1,3-cyclohexanedione ligand was designed and synthesized. The electroluminescent (EL) characteristics of IR-PIQC-1 in the EL device were evaluated. The thin layers of EL devices were fabricated by the vacuum deposition method, and the layer-structures of the devices were ITO/NPD/IR-PIQC-1 or IR-BTPAC (10%) in CBP/Balq/Alq/LiF/Al. Brightness of the IR-PIQC-1 device was 574 cd/m2 at 11 mA/cm2, and the external quantum efficiency was estimated as 5.28% at the same current density. The EL spectrum of the IR-PIQC-1 device was detected at about 620 nm as the maximum peak with red phosphorescence.

Highly Efficient Red Electrophosphorescent Devices Based on Iridium Isoquinoline Complexes: Remarkable External Quantum Efficiency Over a Wide Range of Current

Outstanding performance as an emissive dopant in organic light‐emitting devices is shown by red phosphorescent iridium complexes based on an isoquinoline framework (such as that shown in the Figure). Remarkably high efficiency can be maintained in the devices at high currents with a negligible effect from either triplet–triplet (T–T) annihilation or saturation of the excited states.

High-performance polymer light-emitting diodes doped with a red phosphorescent iridium complex

High efficiency has been achieved in polymer light-emitting diodes (PLEDs) exhibiting red emission by doping a fluorescence host material, poly(vinylcarbazole) (PVK), with an iridium(III) complex, bis[2-(2′-benzothienyl)-pyridinato-N,C3′]iridium(acetylacetonate) (BtpIr). The electroluminescence spectrum has a maximum wavelength of 614 nm. The highest external quantum efficiency is 3.3%. Due to its short triplet excited lifetime (∼5 μs), the quenching of the triplet exciton in BtpIr-doped PVK PLEDs has been shown to be suppressed compared to platinum(II)-2,8,12,17-tetraethyl- 3,7,13,18-tetramethylporphyrin-doped PVK PLEDs. 65% of the peak efficiency can be sustained at high-current density and at the very high brightness of 1350 cd/m2. We suggest that both triplet–triplet annihilation and polaron–triplet annihilation involves exciton quenching.