Near-UV to red-emitting charged bis-cyclometallated iridium(iii) complexes for light-emitting electrochemical cells
Herein we report a series of charged iridium complexes emitting from near-UV to red using carbene-based N^C: ancillary ligands. Synthesis, photophysical and electrochemical properties of this series are described in detail together with X-ray crystal structures. Density Functional Theory calculations show that the emission originates from the cyclometallated main ligand, in contrast to commonly designed charged complexes using bidentate N^N ancillary ligands, where the emission originates from the ancillary N^N ligand. The radiative process of this series of compounds is characterized by relatively low photoluminescence quantum yields in solution that is ascribed to non-radiative deactivati…
Stable Green Electroluminescence from an Iridium Tris-Heteroleptic Ionic Complex
An ionic tris-heteroleptic iridium complex gives green light-emitting electrochemical cells (LECs) with unprecedented performances for this part of the visible spectrum. The devices are very bright (>1000 cd m–2), efficient (∼3%), and stable (>55 h). The novel complex is prepared using a new and efficient synthetic procedure. We show that there is a mixed orbital formation originating from the two different orthometalating ligands resulting in photophysical properties that lie between those of its two bis-heteroleptic analogs. Therefore, tris-heteroleptic complexes provide new avenues for fine-tunning the emission properties and to bridge gaps between a series of bis-heteroleptic complexes.
Ultrafast Relaxation Dynamics of Osmium−Polypyridine Complexes in Solution
We present steady-state absorption and emission spectroscopy and femtosecond broadband photoluminescence up-conversion spectroscopy studies of the electronic relaxation of Os(dmbp)(3) (Os1) and Os(bpy)(2)(dpp) (Os2) in ethanol, where dmbp is 4,4'-dimethyl-2,2'-biypridine, bpy is 2,2'-biypridine, and dpp is 2,3-dipyridyl pyrazine. In both cases, the steady-state phosphorescence is due to the lowest (MLCT)-M-3 state, whose quantum yield we estimate to be <= 5.0 x 10(-3). For Os1, the steady-state phosphorescence lifetime is 25 ns. In both complexes, the photoluminescence excitation spectra map the absorption spectrum, pointing to an excitation wavelength-independent quantum yield. The ultrafa…
White-light phosphorescence emission from a single molecule: application to OLED.
A simple mononuclear cyclometallated iridium(III) complex exhibits white photo- and electro- luminescence in the wavelength range from 440 to 800 nm, which originates from a single emitting excited state of mixed character. Bolink Henk, Henk.Bolink@uv.es ; Coronado Miralles, Eugenio, Eugenio.Coronado@uv.es
Highly phosphorescent perfect green emitting iridium(iii) complex for application in OLEDs.
A novel iridium complex, [bis-(2-phenylpyridine)(2-carboxy-4-dimethylaminopyridine)iridium(III)] (N984), was synthesized and characterized using spectroscopic and electrochemical methods; a solution processable OLED device incorporating the N984 complex displays electroluminescence spectra with a narrow bandwidth of 70 nm at half of its intensity, with colour coordinates of x = 0.322; y = 0.529 that are very close to those suggested by the PAL standard for a green emitter. Bolink, Henk, Henk.Bolink@uv.es ; Coronado Miralles, Eugenio, Eugenio.Coronado@uv.es ; Garcia Santamaria, Sonsoles Amor, Sonsoles.Garcia@uv.es
Efficient orange light-emitting electrochemical cells
We report the first bis-cyclometalated cationic iridium(III) complex with N-aryl-substituted 1H-imidazo [4,5-f][1,10]phenanthroline. The complex emits yellow-orange phosphorescence with a maximum at 583 nm, a quantum yield of 43%, and an excited-state lifetime of 910 ns in argon-saturated dichloromethane. Optimized orange light-emitting electrochemical cells with the new Ir(III) complex exhibit fast turn-on, a peak luminance of 684 cd m(-2) and a peak efficacy of 6.5 cd A(-1); in 850 h of continuous operation their luminance and efficacy decrease only by 20%.
A deep-blue emitting charged bis-cyclometallated iridium(iii) complex for light-emitting electrochemical cells
We report here a new cationic bis-cyclometallated iridium(III) complex, 1, with deep-blue emission at 440 nm and its use in Light-emitting Electrochemical Cells (LECs). The design is based on the 2′,6′-difluoro-2,3′-bipyridine skeleton as the cyclometallating ligand and a bis-imidazolium carbene-type ancillary ligand. Furthermore, bulky tert-butyl substituents are used to limit the intermolecular interactions. LECs have been driven both at constant voltage (6 V) and constant current (2.5 mA cm−2). The performances are significantly improved with the latter method, resulting overall in one of the best reported greenish-blue LECs having fast response (17 s), light intensity over 100 cd m−2 an…
Dual-emitting Langmuir-Blodgett film-based organic light-emitting diodes.
Langmuir-Blodgett (LB) films containing alternating layers of the metallosurfactants bis(4,4'-tridecyl-2,2'-bipyridine)-(4,4'-dicarboxy-2,2'-bipyridine) ruthenium(II)-bis(chloride) (1) and bis[2-(2,4-difluorophenyl)pyridine](4,4'-dinonadecyl-2,2'-bipyridine)iridium(III) chloride (2) have been prepared. Langmuir monolayers at the air-water interface of 1 and 2 with different anions in the subphase have been characterized by pi-A compression isotherms and Brewster angle microscopy (BAM). The transferred LB films have been characterized by IR, UV-vis and emission spectroscopy, and atomic force microscopy (AFM). Electroluminescent devices formed by LB films containing alternating layers of thes…
Observation of Ligand-Centred Fluorescence and Intramolecular Relaxation at Sub-Vibrational Time Scales
Using broadband photoluminescence upconversion, we observe fluorescence from a high-lying ligand-centred state in Ir(ppy)3. This result allows us to clock the electronic relaxation to the lowest 3MLCT state, occurring at sub-vibrational time scales.
Low Current Density Driving Leads to Efficient, Bright and Stable Green Electroluminescence
Electroluminescent devices have the potential to reshape lighting and display technologies by providing low-energy consuming solutions with great aesthetic features, such as flexibility and transparency. In particular, light-emitting electrochemical cells (LECs) are among the simplest electro-luminescent devices. The device operates with air-stable materials and the active layer can be resumed to an ionic phosphorescent emitter. As a consequence, LECs can be assembled using solution-process technologies, which could allow for low-cost and large-area lighting applications in the future. High efficiencies have been reported at rather low luminances (<50 cd m(-2)) and at very low current densi…
An inconvenient influence of iridium(III) isomer on OLED efficiency.
The recently reported heteroleptic cyclometallated iridium(III) complex [Ir(2-phenylpyridine)(2)(2-carboxy-4-dimethylaminopyridine)] N984 and its isomer N984b have been studied more in detail. While photo- and electrochemical properties are very similar, DFT/TDDFT calculations show that the two isomers have different HOMO orbital characteristics. As a consequence, solution processed OLEDs made using a mixture of N984 and isomer N984b similar to vacuum processed devices show that the isomer has a dramatic detrimental effect on the performances of the device. In addition, commonly used thermogravimetric analysis is not suitable for showing the isomerization process. The isomer could impact pe…
Tuning the photophysical properties of cationic iridium(iii) complexes containing cyclometallated 1-(2,4-difluorophenyl)-1H-pyrazole through functionalized 2,2′-bipyridineligands: blue but not blue enough
Four new heteroleptic iridium(III) complexes in the family [Ir(dfppz)(2)((NN)-N-boolean AND)](+), where Hdfppz = 1-(2,4-difluorophenyl)-1H-pyrazole and (NN)-N-boolean AND = 6-phenyl-2,2'-bipyridine (1), 4,4'-(di-tert-butyl)-6-phenyl-2,2'-bipyridine (2), 4,4'-(di-tert-butyl)-6,6'-diphenyl-2,2'-bipyridine (3) and 4,4'-bis(dimethylamino)-2,2'-bipyridine (4), have been synthesized as the hexafluoridophosphate salts and fully characterized. Single crystal structures of ligand 3 and the precursor [Ir-2(dfppz)(4)(mu-Cl)(2)] have been determined, along with the structures of the complexes 4{[Ir(dfppz)(2)(1)][PF6]}center dot 3CH(2)Cl(2), [Ir(dfppz)(2)(3)][PF6]center dot CH2Cl2 and [Ir(dfppz)(2)(4)][…
Ligand-Centred Fluorescence and Electronic Relaxation Cascade at Vibrational Time Scales in Transition-Metal Complexes
Using femtosecond-resolved photoluminescence up-conversion, we report the observation of the fluorescence of the high-lying ligand-centered (LC) electronic state upon 266 nm excitation of an iridium complex, Ir(ppy)(3), with a lifetime of 70 +/- 10 fs. It is accompanied by a simultaneous emission of all lower-lying electronic states, except the lowest triplet metal-to-ligand charge-transfer ((MLCT)-M-3) state that shows a rise on the same time scale. Thus, we observe the departure, the intermediate steps, and the arrival of the relaxation cascade spanning similar to 1.6 eV from the (LC)-L-1 state to the lowest 3MLCT state, which then yields the long-lived luminescence of the molecule. This …
Correlating the Lifetime and Fluorine Content of Iridium(III) Emitters in Green Light-Emitting Electrochemical Cells
In light-emitting electrochemical cells, the lifetime of the device is intrinsically linked to the stability of the phosphorescent emitter. In this study, we present a series of ionic iridium(III) emitters based on cyclometalating phenylpyridine ligands whose fluorine substituents are varied in terms of position and number. Importantly, despite these structural modifications, the emitters exhibit virtually identical electrochemical and spectroscopic properties, which allows for proper comparison in functional devices. Quantum chemical calculations support the properties measured in solution and suggest great similarities regarding the electronic structures of the emitters. In electrolumines…
Fluorine-free blue-green emitters for light-emitting electrochemical cells
Date of Acceptance: 29/05/2014 There is presently a lack of efficient and stable blue emitters for light-emitting electrochemical cells (LEECs), which limits the development of white light emitting systems for lighting. Cyclometalated iridium complexes as blue emitters tend to show low photoluminescence efficiency due to significant ligand-centred character of the radiative transition. The most common strategy to blue-shift the emission is to use fluorine substituents on the cyclometalating ligand, such as 2,4-difluorophenylpyridine, dFppy, which has been shown to decrease the stability of the emitter in operating devices. Herein we report a series of four new charged cyclometalated iridium…
An Ester-Substituted Iridium Complex for Efficient Vacuum-Processed Organic Light-Emitting Diodes
An orange-red-emitting iridium complex (N958) was prepared, and its photophysical and device-based characteristics were investigated. Despite N958 displaying quite poor photophysical properties in solution (acetonitrile), organic light-emitting diode (OLED) devices based on the complex exhibit an efficiency close to 10%.
CCDC 968510: Experimental Crystal Structure Determination
Related Article: Filippo Monti, Florian Kessler, Manuel Delgado, Julien Frey, Federico Bazzanini, Gianluca Accorsi, Nicola Armaroli, Henk J. Bolink, Enrique Ortí, Rosario Scopelliti, Md. Khaja Nazeeruddin, and Etienne Baranoff|2013|Inorg.Chem.|52|10292|doi:10.1021/ic400600d
CCDC 1546695: Experimental Crystal Structure Determination
Related Article: Adam F. Henwood, Amlan K. Pal, David B. Cordes, Alexandra M. Z. Slawin, Thomas W. Rees, Cristina Momblona, Azin Babaei, Antonio Pertegás, Enrique Ortí, Henk J. Bolink, Etienne Baranoff, Eli Zysman-Colman|2017|J.Mater.Chem.C|5|9638|doi:10.1039/C7TC03110F
CCDC 1546696: Experimental Crystal Structure Determination
Related Article: Adam F. Henwood, Amlan K. Pal, David B. Cordes, Alexandra M. Z. Slawin, Thomas W. Rees, Cristina Momblona, Azin Babaei, Antonio Pertegás, Enrique Ortí, Henk J. Bolink, Etienne Baranoff, Eli Zysman-Colman|2017|J.Mater.Chem.C|5|9638|doi:10.1039/C7TC03110F
CCDC 968508: Experimental Crystal Structure Determination
Related Article: Filippo Monti, Florian Kessler, Manuel Delgado, Julien Frey, Federico Bazzanini, Gianluca Accorsi, Nicola Armaroli, Henk J. Bolink, Enrique Ortí, Rosario Scopelliti, Md. Khaja Nazeeruddin, and Etienne Baranoff|2013|Inorg.Chem.|52|10292|doi:10.1021/ic400600d
Blue-Emitting Cationic Iridium(III) Complexes Featuring Pyridylpyrimidine Cyclometalating Ligands and their Use in Sky-Blue and Blue-Green Light-Emitting Electrochemical Cells (LEECs) and Organic Light-Emitting Diodes (OLEDs) (dataset)
CCDC 968506: Experimental Crystal Structure Determination
Related Article: Filippo Monti, Florian Kessler, Manuel Delgado, Julien Frey, Federico Bazzanini, Gianluca Accorsi, Nicola Armaroli, Henk J. Bolink, Enrique Ortí, Rosario Scopelliti, Md. Khaja Nazeeruddin, and Etienne Baranoff|2013|Inorg.Chem.|52|10292|doi:10.1021/ic400600d
CCDC 1546698: Experimental Crystal Structure Determination
Related Article: Adam F. Henwood, Amlan K. Pal, David B. Cordes, Alexandra M. Z. Slawin, Thomas W. Rees, Cristina Momblona, Azin Babaei, Antonio Pertegás, Enrique Ortí, Henk J. Bolink, Etienne Baranoff, Eli Zysman-Colman|2017|J.Mater.Chem.C|5|9638|doi:10.1039/C7TC03110F
CCDC 1546697: Experimental Crystal Structure Determination
Related Article: Adam F. Henwood, Amlan K. Pal, David B. Cordes, Alexandra M. Z. Slawin, Thomas W. Rees, Cristina Momblona, Azin Babaei, Antonio Pertegás, Enrique Ortí, Henk J. Bolink, Etienne Baranoff, Eli Zysman-Colman|2017|J.Mater.Chem.C|5|9638|doi:10.1039/C7TC03110F
CCDC 968507: Experimental Crystal Structure Determination
Related Article: Filippo Monti, Florian Kessler, Manuel Delgado, Julien Frey, Federico Bazzanini, Gianluca Accorsi, Nicola Armaroli, Henk J. Bolink, Enrique Ortí, Rosario Scopelliti, Md. Khaja Nazeeruddin, and Etienne Baranoff|2013|Inorg.Chem.|52|10292|doi:10.1021/ic400600d
CCDC 968505: Experimental Crystal Structure Determination
Related Article: Filippo Monti, Florian Kessler, Manuel Delgado, Julien Frey, Federico Bazzanini, Gianluca Accorsi, Nicola Armaroli, Henk J. Bolink, Enrique Ortí, Rosario Scopelliti, Md. Khaja Nazeeruddin, and Etienne Baranoff|2013|Inorg.Chem.|52|10292|doi:10.1021/ic400600d
CCDC 968509: Experimental Crystal Structure Determination
Related Article: Filippo Monti, Florian Kessler, Manuel Delgado, Julien Frey, Federico Bazzanini, Gianluca Accorsi, Nicola Armaroli, Henk J. Bolink, Enrique Ortí, Rosario Scopelliti, Md. Khaja Nazeeruddin, and Etienne Baranoff|2013|Inorg.Chem.|52|10292|doi:10.1021/ic400600d