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Blue-green-emitting cationic iridium complexes with oxadiazole-type counter-anions and their use for highly efficient solution-processed organic light-emitting diodes
摘要： Cationic iridium complexes are promising phosphorescent dopants for solution-processed organic light-emitting diodes (OLEDs) and counter-anion control has emerged as a facile approach to tailor their properties for high-performance devices. A series of oxadiazole-type anions, 3-(5-phenyl-1,3,4-oxadiazol-2-yl)benzenesulfonate (OXD-SO3?), 3-(5-(4-(tert-butyl)phenyl)-1,3,4-oxadiazol-2-yl)benzenesulfonate (tBuOXD-SO3?) and (3-(5-(4-(tert-butyl)phenyl)-1,3,4-oxadiazol-2-yl)phenyl)trifluoroborate (tBuOXD-BF3?), have been prepared as counter-anions for blue-green-emitting cationic iridium complexes. The photophysical and electrochemical properties of the anions and the complexes have been comprehensively characterized. The anions do not affect the emission properties of the phosphorescent cation and efficiently transfer their energy to the cations in films. Solution-processed, double-layer OLEDs using the complexes as dopants have shown much higher (～1.4) efficiencies than the device using the reference complex with a PF6? counter-anion, owing to the improvement of carrier transport/recombination balance by the electron-trapping effect of oxadiazole-type anions. In particular, the blue-green device using the complex with the OXD-SO3? counter-anion affords a peak current efficiency of 37.6 cd A?1 and a peak external quantum efficiency (EQE) of 15.2%, which is the highest for solution-processed OLEDs based on cationic iridium complexes reported so far.
关键词： solution-processed OLEDs,oxadiazole-type counter-anions,phosphorescent dopants,cationic iridium complexes,high-performance devices
更新于2025-11-14 15:23:50
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Comparison of Structural and Optical Properties for N-embedded Polycyclic and Non-embedded Cationic Phosphorescent Iridium(III) Complexes
摘要： We designed and synthesized N-embedded polycyclic based cationic Ir-NO and non-embedded complexes Ir-N and Ir-O. Single crystal structures indicate that the N-embedded polycyclic unit in Ir-NO exhibits certain planarity and induces interesting π-π-stackings between 2,2’-bipyridine moieties of one molecule and two polycyclic units of the other molecule, and their shortest intermolecular distances are both 3.24 ?, which results in a stronger structural distortion of 2,2’-bipyridine ligand with a larger torsion angel (12.70o) in comparison with those of Ir-N (5.51o) and Ir-O (8.11o). Unpredictably, both Ir-N and Ir-O show deep red emission in solution whereas Ir-NO exhibits no emission. However, all complexes show significant luminescence in their respective polystyrene (PS) films, and Ir-NO displays a longer emission lifetime than those of Ir-N and Ir-O. DFT calculations reveal that unusual ligand-to-metal charge transfer (3LMCT) excited state character can be found in Ir-NO and Ir-N, which is in contrast to metal-to-ligand charge transfer (3MLCT) excited state property in Ir-O.
关键词： iridium complexes,N-embedded polycyclic ligands,phosphorescent cationic,polystyrene films
更新于2025-09-19 17:15:36
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Tuning the electrochemiluminescent properties of iridium complexes of N-heterocyclic carbene ligands
摘要： A series of five heteroleptic Ir(III) complexes of the general form Ir(dfppy)2(C^C) have been prepared (where dfppy represents 2-(2,4-difluorophenyl)pyridine and C^C represents a bidentate cyclometalated phenyl substituted imidazolylidene ligand). The cyclometalated phenyl ring of the imidazolylidene ligand was either unsubstituted or substituted with electron donating (OMe and Me) or electron withdrawing (Cl and F) groups in the 2 and 4 positions. The synthesised Ir(III) complexes have been characterised by elemental analysis, NMR spectroscopy, cyclic voltammetry and electronic absorption and emission spectroscopy. The molecular structures for four Ir(III) complexes were determined by single crystal X-ray diffraction. Each of the Ir(III) complexes exhibited intense photoluminescence in acetonitrile solution at room temperature with quantum yields (ΦPL) ranging from 58% to 86%. Cyclic voltammetry experiments revealed one oxidation process (formally ascribed to the metal centre), and two ligand-based reductions for each complex. Complexes 1–5 gave moderate to intense annihilation and co-reactant electrochemiluminescence (ECL). Consideration of the electrochemical, spectroscopic and theoretical investigations provide insights into the electrochemiluminescence behaviour.
关键词： iridium complexes,electrochemiluminescence,cyclic voltammetry,photoluminescence,N-heterocyclic carbene ligands
更新于2025-09-19 17:15:36
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Recent Development in Optoelectronic Devices || Introductory Chapter: Iridium Complexes as Organic Light Emitting Diodes (OLEDs): A Theoretical Analysis
摘要： A specific discipline of electronics, which focus on light-emitting or light-detecting devices, the term “Optoelectronics” is used in the broader perspective. Such devices include those that emit light (LEDs and light bulbs), channel light (fiber optic cables), detect light (photodiodes and photoresistors), or are controlled by light (optoisolators and phototransistors). An interesting combination of electronics and optics, Optoelectronics find varied applications in telecommunications, military services, medical field, solid state devices (sensors, IR emitters, and laser emitters), and automatic control systems. The other counterparts as photo resistors and photovoltaic devices are also used for various applications. Nowadays, photodetectors has confronted significant challenges regarding the realization of efficient and sensitive detection with low-noise for the ultraviolet (UV), visible, and infrared regimes of electromagnetic spectrum.
关键词： OLEDs,Optoelectronics,Phosphorescent Emission,Iridium Complexes,Theoretical Analysis
更新于2025-09-19 17:13:59
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Dibenzofuran-based iridium complexes as green emitters: Realizing PhOLEDs with high power efficiency and extremely low efficiency roll-off
摘要： In this work, a series of novel iridium (III) cyclometallated complexes BF-Ir1, BF-Ir2 and BF-Ir3 is developed by introducing a dibenzofuran moiety into the main ligand. The photophysical, thermal, and electroluminescent properties of these iridium (III) complexes are systematically investigated. Notably, the phosphorescent organic light-emitting diodes (PhOLEDs) with BF-Ir1, BF-Ir2 and BF-Ir3 as the green emitters displayed the maximum EQEs of 15.1%, 23.7% and 21.5%, respectively. In addition, an impressively high PE up to 96.8 lm W?1 is achieved in the device based on BF-Ir3. When the luminance reached 1000 and 10000 cd m?2, the corresponding EQE values of BF-Ir3-based PhOLEDs could be maintained at 20.7% and 18.5%. These results clearly demonstrate that dibenzofuran-based iridium (III) complexes have great potential for their application as green emitters in PhOLEDs to realize both high EQE and PE as well as low efficiency roll-off.
关键词： Iridium complexes,Power efficiency,PhOLEDs,Dibenzofuran
更新于2025-09-19 17:13:59
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Elucidating the Non-Radiative Deactivation Pathways in a Cationic Iridium Complex with 2,4-di(1 <i>H</i> -pyrazol-1-yl)Pyridine as the Ancillary Ligand
摘要： Deep insight into the non-radiative deactivation pathways in phosphorescent cationic iridium complexes is critically important for developing efficient blue-emitting complexes toward advanced applications. Here, we report the synthesis, photophysical and electrochemical characterizations of a blue-green-emitting cationic iridium complex [Ir(ppy)2(bipzpy)]PF6 (Hppy is 2-phenylpyridine and bipzpy is 2,4-di(1H-pyrazol-1-yl)pyridine). The non-radiative deactivation pathways in [Ir(ppy)2(bipzpy)]PF6 have been elucidated through extensive density functional theory calculations. The calculations reveal that the higher-lying charge-transfer (CT) state in [Ir(ppy)2(bipzpy)]PF6, which arises from Ir/ppy→bipzpy transitions, favors non-radiative deactivation because of its large structural distortion compared to the ground state. Both the CT state and the dark metal-centered (3MC) state can be thermally accessed by the lowest-lying emitting triplet state at room temperature, with the former being much more easily accessible, which causes additional non-radiative deactivations for the emitting triplet state. The active roles of the CT and 3MC states in the non-radiative deactivation pathways are, for the first time, confirmed in such blue-emitting complexes with pzpy-type ancillary ligands (pzpy is 2-(1H-pyrazol-1-yl)pyridine).
关键词： charge-transfer state,metal-centered state,density functional theory,blue-emitting complexes,phosphorescent cationic iridium complexes,non-radiative deactivation
更新于2025-09-10 09:29:36
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Excited-State Switching between Ligand-Centered and Charge Transfer Modulated by Metal–Carbon Bonds in Cyclopentadienyl Iridium Complexes
摘要： Three series of pentamethylcyclopentadienyl (Cp*) Ir(III) complexes with different bidentate ligands were synthesized and structurally characterized, [Cp*Ir(tpy)L]n+ (tpy = 2-tolylpyridinato; n = 0 or 1), [Cp*Ir(piq)L]n+ (piq = 1-phenylisoquinolinato; n = 0 or 1), and [Cp*Ir(bpy)L]m+ (bpy = 2,2′-bipyridine; m = 1 or 2), featuring a range of monodentate carbon-donor ligands within each series [L = 2,6-dimethylphenylisocyanide; 3,5-dimethylimidazol-2-ylidene (NHC); methyl)]. The spectroscopic and photophysical properties of these molecules and those of the photocatalyst [Cp*Ir(bpy)H]+ were examined to establish electronic structure?photophysical property relationships that engender productive photochemical reactivity of this hydride and its methyl analogue. The Ir(III) chromophores containing ancillary CNAr ligands exhibited features anticipated for predominantly ligand-centered (LC) excited states, and analogues bearing the NHC ancillary exhibited properties consistent with LC excited states containing a small admixture of metal-to-ligand charge-transfer (MLCT) character. However, the molecules featuring anionic and strongly σ-donating methyl or hydride ligands exhibited photophysical properties consistent with a high degree of CT character. Density functional theory calculations suggest that the lowest energy triplet states in these complexes are composed of a mixture of MLCT and ligand-to-ligand CT originating from both the Cp* and methyl or hydride ancillary ligands. The high degree of CT character in the triplet excited states of methyliridium complexes bearing C^N-cyclometalated ligands offer a striking contrast to the photophysical properties of pseudo-octahedral structures fac-Ir(C^N)3 or Ir(C^N)2(acac) that have lowest-energy triplet excited states characterized as primarily LC character with a more moderate MLCT admixture.
关键词： cyclopentadienyl iridium complexes,charge transfer,photophysical properties,Iridium(III) complexes,ligand-centered excited states
更新于2025-09-09 09:28:46