Two novel orange cationic iridium(III) complexes with multifunctional ancillary ligands used for polymer light-emitting diodes

Tang, Huaijun; Li, Yanhu; Zhao, Baofeng; Yang, Wei; Wu, Hongbin; Cao, Yong

doi:10.1016/j.orgel.2012.09.035

Cited by 39 publications

(24 citation statements)

References 40 publications

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“…For complex 2,C Ei s 32.29 cd A À1 at 10 3 cd m À2 ,w hich then reduces to 23.22 cd A À1 at 10 4 cd m À2 ,s uggesting an attenuation of 28.1 % ( Figure 7). [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] …”

Section: Quantum Chemical Calculationsmentioning

confidence: 99%

“…[35][36][37][38][39][40] However,i TMCs were deemed hard to evaporate due to their intrinsici onic nature and henceo nly appliedf or OLEDs with solution-processed rather than vacuum-deposited emissive material layers (EMLs), [41][42][43][44][45][46][47][48][49][50][51] until Wong et al and Zhang et al successively reported sublimable cationic iridium(III) complexes with large-sized ligands chelated to the iridium core. [35][36][37][38][39][40] However,i TMCs were deemed hard to evaporate due to their intrinsici onic nature and henceo nly appliedf or OLEDs with solution-processed rather than vacuum-deposited emissive material layers (EMLs), [41][42][43][44][45][46][47][48][49][50][51] until Wong et al and Zhang et al successively reported sublimable cationic iridium(III) complexes with large-sized ligands chelated to the iridium core.…”

Section: Introductionmentioning

confidence: 99%

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Toward High‐Performance Vacuum‐Deposited OLEDs: Sublimable Cationic Iridium(III) Complexes with Yellow and Orange Electroluminescence

Zhang

Liu

et al. 2018

Chemistry A European J

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Great advances in the development of efficient luminescent materials are the driving force behind organic light-emitting diodes (OLEDs). Sublimable ionic transition-metal complexes (iTMCs) have emerged as a large family of new emissive dopants applied for vacuum-deposited OLEDs, while the achievement of excellent performance remains arduous. A series of novel sublimable cationic iridium(III) complexes have been designed and synthesized, containing an imidazole-type ancillary ligand and tetraphenylborate-type negative counter-ions with large steric hindrance and well-dispersed charges. The photophysical properties, electrochemical behaviors, and thermal stability are fully investigated and discussed, then demonstrated by theoretical calculations. Yellow- and orange-emitting OLEDs thereof are fabricated by vacuum evaporation deposition, realizing a high external quantum efficiency of up to 11 %, maximum brightness over 27.3×10 cd m and low turn-on voltages below 2.4 V, among the best results of analogous phosphorescent OLEDs based on iTMCs. This work indicates the promising applications of sublimable iTMCs in state-of-the-art vacuum-deposited optoelectronic devices.

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Section: Quantum Chemical Calculationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Toward High‐Performance Vacuum‐Deposited OLEDs: Sublimable Cationic Iridium(III) Complexes with Yellow and Orange Electroluminescence

Zhang

Liu

et al. 2018

Chemistry A European J

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“…19 Film PL spectra resembled those of solutions except for a small red-shift (2-8 nm), which was probably caused by greater intermolecular interactions due to smaller distances between molecules in films. 20 Table 3 lists the PL results of Ir1 and Ir2 complexes and of reported analogs containing the same main ligand (bt) but different ancillary ligands, and thus, provides an overview of the emission wavelengths of cyclometallated iridium complexes. Ir1 and Ir2 complexes emitted blue-green phosphorescence, which was 54-67 nm blue-shifted emission versus those of (bt) 2 Ir(acac) and (bt) 2 Ir(pic) which are neutral cyclometallated iridium(III) complexes containing bt main ligand.…”

Section: Resultsmentioning

confidence: 99%

Photophysical Properties of Highly Efficient Blue-Green Emitting Cationic Iridium (III) Complexes Containing Two 2-Phenylbenzothiazole Ligands and One Diphosphine Ligand

Yun¹,

Song²,

Kim³

et al. 2014

Bulletin of the Korean Chemical Society

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Two novel phosphorescent heteroleptic cationic Ir(III) complexes, Ir(bt) 2 (dmpe) (Ir1) and Ir (bt) 2 (dppe) (Ir2), where bt is 2-phenylbenzothiazole, dmpe is 1,2-bis(dimethylphosphino)ethane, and dppe is 1,2-bis(diphenylphosphino)ethane, were designed and synthesized. Their photophysical and electrochemical properties and the X-ray structure of the Ir1 complex were investigated. The prepared Ir(III) complexes exhibited blue-green emissions at 503-538 nm with vibronic fine structures in dichloromethane solution and PMMA film, implying that the lowest excited states are dominated by ligand-based 3 π-π* transitions. The π-acceptor ability of the diphosphine ancillary ligand leads to blue-shift emission. The room temperature photoluminescent quantum yields (PLQYs) of Ir1 and Ir2 were 52% and 45%, respectively, in dichloromethane solution. These high PLQYs resulted from steric hindrances by the bulky cationic iridium complexes. The crystal structure of Ir1 was determined by X-ray crystallography, which revealed that central iridium adopted a distorted octahedral structure coordinated with two bt ligands (N^C) and one dmpe ligand (P^P) showing cis C-C and trans N-N dispositions. The bent nature of the dmpe ligand resulted in a relatively wide bite angle of 83.83 o of P-Ir-P.

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“…33--39 To the best of our knowledge the best performing solution--processed device using a cationic iridium complex as the emitter showed a maximum EQE of 7.1% and CE of 10.0 cd/m 2 . 39 This device used [Ir(npy) 2 (c--phen)]PF 6 , (npy is 2--(naphthalen--1--yl)pyridinato c-- 10]phenanthroline). Due to the use of strongly conjugated C^N ligands the emission colour of the device was in the red region with CIE coordinates of (0.57, 0.40) 39 and so a direct comparison to the current devices is not appropriate.…”

Section: Device Fabricationmentioning

confidence: 99%

“…39 This device used [Ir(npy) 2 (c--phen)]PF 6 , (npy is 2--(naphthalen--1--yl)pyridinato c-- 10]phenanthroline). Due to the use of strongly conjugated C^N ligands the emission colour of the device was in the red region with CIE coordinates of (0.57, 0.40) 39 and so a direct comparison to the current devices is not appropriate. Recently, Duan and co--workers reported the use of the blue--green [Ir(ppy) 2 (pzpy)][PF 6 ] (pzpy = 2--(1Hpyrazol--1--yl)pyridine) complex as the emitter in a a single--layer solution--processed OLED.…”

Section: Device Fabricationmentioning

confidence: 99%

Controlling the emission efficiency of blue-green iridium(iii) phosphorescent emitters and applications in solution-processed organic light-emitting diodes

et al. 2016

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We show that the emission efficiency of blue--green phosphorescent emitters can be controlled through coupling of the excited state to vibrational modes. We controlled this vibrational coupling through choice of different ligands and as a result, complexes with CF 3 --groups on the ancillary ligand were essentially non--emissive (Φ PL < 1%), whereas with isosteric CH 3 --groups the complexes were strongly emissive (Φ PL > 50%). Emission of the complexes can be drastically improved (30 times higher Φ PL compared to degassed solution for the CF 3 --containing complexes) by blending them with an inert solid host such as PMMA, which mitigates metal--ligand vibrations. Solution--processed organic light--emitting diodes made from these materials showed efficiency as high as 6.3%. Page 14 of 44 Journal of Materials Chemistry C Journal Name ARTICLEThis journal is © The Royal Society of Chemistry 20xxJ. Name., 2013, 00, 1--3 | 2Please do not adjust marginsPlease do not adjust margins IntroductionIridium complexes have attracted significant attention as potent emitters in organic light--emitting diodes (OLEDs) 1--3 and light--emitting electrochemical cells (LEECs), 4--7 which are electroluminescent devices targeted for next generation flat panel displays and solid--state lighting. This is due to their high photoluminescence quantum yield (Φ PL ) and short radiative lifetime, facile colour tunability across the entirety of the visible spectrum, and good thermal and photo stability. 8 Importantly, both singlet and triplet excitons in these complexes contribute to device efficiencies, 9--12 which enables them to attain nearly 100% internal quantum efficiency. 13 However, the reported OLEDs based on iridium complexes can in many cases show low device efficiency due to rapid non--radiative decay. 10,14,15 One reason for the reduced efficiencies observed is due to enhanced coupling of the excited state to vibrational modes. 10,14--16 Many different methods such as controlling isomer geometry or using rigid structures including inert hosts like poly(methylmethacrylate) (PMMA) and poly(styrene) have been reported for controlling the magnitude of vibrational coupling, which lead to moderate improvement of the quantum yield. 1,17 However, in order to establish a structure--property relationship for achieving both high Φ PL and device efficiency, detailed photophysical and device studies on structurally related complexes are required. Here we show that blue--green cationic iridium(III) complexes of the form [Ir(C^N) 2 (N^N)]PF 6 with the same cyclometallating, C^N, ligands but with different saturated strongly--donating guanidylpyridine (gpy) N^N ligands 18 can be used to control the emission efficiency. We find that there is severe quenching of PL in complexes with a CF 3 on the gpy ligand in solution, which we attribute to vibrational coupling. We show that this can be overcome by embedding the complex in an inert matrix. Therefore, we embedded the complexes within PMMA and observed a significant enhancement of the ...

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Two novel orange cationic iridium(III) complexes with multifunctional ancillary ligands used for polymer light-emitting diodes

Cited by 39 publications

References 40 publications

Toward High‐Performance Vacuum‐Deposited OLEDs: Sublimable Cationic Iridium(III) Complexes with Yellow and Orange Electroluminescence

Toward High‐Performance Vacuum‐Deposited OLEDs: Sublimable Cationic Iridium(III) Complexes with Yellow and Orange Electroluminescence

Photophysical Properties of Highly Efficient Blue-Green Emitting Cationic Iridium (III) Complexes Containing Two 2-Phenylbenzothiazole Ligands and One Diphosphine Ligand

Controlling the emission efficiency of blue-green iridium(iii) phosphorescent emitters and applications in solution-processed organic light-emitting diodes

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