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1.
Chem Commun (Camb) ; 55(85): 12873-12876, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31599287

RESUMO

A brand new europium(iii) ß-diketonate complex undergoes a single-crystal-to-single-crystal transformation via [2+2] cycloaddition after UV irradiation, triggering strong Eu(iii) red emission turn-on, which is highly photostable even after 50 hours of irradiation. A photo-patterning process is successfully conducted for security printing application in materials science.

2.
Artigo em Inglês | MEDLINE | ID: mdl-31559680

RESUMO

Pure organic materials with intrinsic room-temperature phosphorescence typically rely on heavy atoms or heteroatoms. Two different strategies towards constructing organic room-temperature phosphorescence (RTP) species based upon the through-space charge transfer (TSCT) unit of [2.2]paracyclophane (PCP) were demonstrated. Materials with bromine atoms, PCP-BrCz and PPCP-BrCz, exhibit RTP lifetime of around 100 ms. Modulating the PCP core with non-halogen-containing electron-withdrawing units, PCP-TNTCz and PCP-PyCNCz, successfully elongate the RTP lifetime to 313.59 and 528.00 ms, respectively, the afterglow of which is visible for several seconds under ambient conditions. The PCP-TNTCz and PCP-PyCNCz enantiomers display excellent circular polarized luminescence with dissymmetry factors as high as -1.2×10-2 in toluene solutions, and decent RTP lifetime of around 300 ms for PCP-TNTCz enantiomers in crystalline state.

3.
Chem Commun (Camb) ; 55(57): 8215-8218, 2019 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-31231733

RESUMO

Two series of chiral cyclometalated iridium(iii) complexes based on sulfur atom containing enantiopure BINOL derivatives were rapidly synthesized, which are endowed with varied chiroptical properties. Moreover, the circularly polarized OLEDs using enantiomers show a maximum luminance of above 40 000 cd m-2 and an external quantum efficiency of 23.6% with low efficiency roll-off as well as obvious CPEL properties.

4.
ACS Appl Mater Interfaces ; 11(22): 20192-20199, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-31070035

RESUMO

Three iridium(III) complexes (Ir(4tfmpq)2mND, Ir(4tfmpq)2mmND, and Ir(4tfmpq)2mpND) with the 4-(4-(trifluoromethyl)phenyl)quinazoline (4tfmpq) main ligand and 1,5-naphthyridin-4-ol derivatives (mND: 8-methyl-1,5-naphthyridin-4-ol, mmND: 2,8-dimethyl-1,5-naphthyridin-4-ol, mpND: 8-methyl-2-phenyl-1,5-naphthyridin-4-ol) as ancillary ligands were studied. The complexes (Ir(4tfmpq)2mND, Ir(4tfmpq)2mmND, and Ir(4tfmpq)2mpND) emit pure red emissions of 626-630 nm with high photoluminescence quantum yields of 85.2-93.4% in CH2Cl2 and better electron mobilities than that of tri(8-hydroxyquinoline)aluminum. By employing three pure red emitters, all the phosphorescent organic light-emitting diodes exhibited superior performances with a maximum external quantum efficiency of 31.48% and the efficiency roll-off is very mild, which are among the best results ever reported for pure red organic light-emitting diodes using Ir(III) complexes. In addition, CIE( x, y) coordinates of (0.670, 0.327) are also close to the standard red emission required by the National Television System Committee.

5.
Dalton Trans ; 48(22): 7583-7588, 2019 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-31066420

RESUMO

In this work, with sulfur-containing ancillary ligands of triethylamine salts of bis(4-methoxyphenyl)-phosphinodithioic acid (omess) and bis(3,5-di-tert-butyl-4-methoxyphenyl)phosphinodithioic acid (tbuss), two four-membered red iridium(iii) complexes (tfmpqz)2Ir(omess) and (tfmpqz)2Ir(tbuss) with Ir-S-P-S structures were synthesized rapidly at room temperature within 5 min, in which 4-(4-(trifluoromethyl)phenyl)quinazoline (tfmpqz) was used as the main ligand. The calculated Gibbs free energy changes of the complex formation reactions prove that they are exothermic and thermodynamically beneficial processes. Both Ir(iii) complexes show almost the same PL emissions at 624 and 623 nm with high phosphorescence quantum yields of 0.60 and 0.72, respectively. Using the two complexes as emitters, both organic light-emitting devices (OLEDs) with the structure of ITO/HATCN (hexaazatriphenylenehexacabonitrile, 5 nm)/TAPC ((bis(4-(N,N-ditolylamino)phenyl)cyclohexane, 30 nm)/(tfmpqz)2Ir(omess) or (tfmpqz)2Ir(tbuss):26DCzppy (2,6-bis-(3-(carbazol-9-yl)phenyl)pyridine) (12 wt%, 10 nm)/TmPyPB (1,3,5-tri((3-pyridyl)-phen-3-yl)benzene, 30 nm)/LiF (1 nm)/Al (100 nm) achieve good performances. Particularly, due to the introduction of tert-butyl groups into the (tfmpqz)2Ir(tbuss) complex, its device exhibits better device properties with a maximum luminance of 26 184 cd m-2, maximum current efficiency of 30.24 cd A-1, maximum power efficiency of 22.61 lm W-1 and maximum external quantum efficiency of 21.50% with CIE coordinates at (0.65, 0.34).

6.
Adv Mater ; 31(28): e1900524, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31106503

RESUMO

Circularly polarized organic light-emitting diodes (CP-OLEDs) are particularly favorable for the direct generation of CP light, and they demonstrate a promising application in 3D display. However, up to now, such CP devices have suffered from low brightness, insufficient efficiency, and serious efficiency roll-off. In this study, a pair of octahydro-binaphthol (OBN)-based chiral emitting enantiomers, (R/S)-OBN-Cz, are developed by ingeniously merging a chiral source and a luminophore skeleton. These chirality-acceptor-donor (C-A-D)-type and rod-like compounds concurrently generate thermally activated delayed fluorescence with a small ΔEST of 0.037 eV, as well as a high photoluminescence quantum yield of 92% and intense circularly polarized photoluminescence with dissymmetry factors (|gPL |) of ≈2.0 × 10-3 in thin films. The CP-OLEDs based on (R/S)-OBN-Cz enantiomers not only display obvious circularly polarized electroluminescence signals with a |gEL | of ≈2.0 × 10-3 , but also exhibit superior efficiencies with maximum external quantum efficiency (EQEmax ) up to 32.6% and extremely low efficiency roll-off with an EQE of 30.6% at 5000 cd m-2 , which are the best performances among the reported CP devices to date.

7.
Dalton Trans ; 48(26): 9744-9750, 2019 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-30984967

RESUMO

The lack of efficient blue-emitting materials is one of the most important issues faced when extending the application of organic light-emitting diodes (OLEDs). Therefore, in this study, the ancillary ligand bis(diphenylphorothioyl)amide (Stpip) was utilized in iridium(iii) complexes with 2-(2,4-difluorophenyl)pyridine (dfppy) and 2-(2,4-difluorophenyl)pyrimidine (dfppm) as the main ligands, respectively. The two complexes, (dfppy)2Ir(Stpip) and (dfppm)2Ir(Stpip), exhibit sky-blue emission peaks at 466 and 474 nm with photoluminescence quantum yields of 12% and 89%, respectively. Due to the strong coordination capability between sulfur and iridium atoms, both complexes can be prepared with extremely high production yields under mild conditions. Furthermore, a double light-emitting layer device using (dfppm)2Ir(Stpip) as the emitter exhibits a maximum external quantum efficiency (EQEmax) of 19.4% with Commission Internationale de l'Eclairage (CIE) coordinates of (0.13, 0.27). Specifically, the EQE remains at 19.2% at a practical brightness of 1000 cd m-2, indicating an inappreciable efficiency roll-off.

8.
Chemistry ; 25(22): 5672-5676, 2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-30829426

RESUMO

Chiral materials with circularly polarized luminescence (CPL) are potentially applicable for 3D displays. In this study, by decorating the pyridinyl-helicene ligands with -CF3 and -F groups, the platinahelicene enantiomers featured superior configurational stability, as well as high sublimation yield (>90 %) and clear CPPL properties, with dissymmetry factors (|gPL |) of approximately 3.7×10-3 in solution and about 4.1×10-3 in doped film. The evaporated circularly polarized phosphorescent organic light-emitting diodes (CP-PhOLEDs) with two enantiomers as emitters exhibited symmetric CPEL signals with |gEL | of (1.1-1.6)×10-3 and decent device performances, achieving a maximum brightness of 11 590 cd m-2 , a maximum external quantum efficiency up to 18.81 %, which are the highest values among the reported devices based on chiral phosphorescent PtII complexes. To suppress the effect of reverse CPEL signal from the cathode reflection, the further implementation of semitransparent aluminum/silver cathode successfully boosts up the |gEL | by over three times to 5.1×10-3 .

9.
Dalton Trans ; 48(5): 1892-1899, 2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30652714

RESUMO

Two new cyclometalated platinum(ii) complexes ((TN3T)Pt(dptp), (4tfmppy)Pt(dptp)) with 2',6'-bis(trifluoromethyl)-2,3'-bipyridine (TN3T) and 4-trifluoromethylphenylpyridine (4tfmppy) as the cyclometalated ligands and the nitrogen heterocycle 2-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)phenol (dptp) as the ancillary ligand were developed. Both complexes are green phosphors with high photoluminescence quantum efficiency yields (λmax = 532 nm, Φp = 65% for (TN3T)Pt(dptp) and λmax = 502 nm, Φp = 71% for (4tfmppy)Pt(dptp)) in CH2Cl2 solutions at room temperature, respectively. Organic light-emitting diodes (OLEDs) with single-emitting layer and double-emitting layer structures were fabricated with good performances. Particularly, the double-emitting layer device D2 based on the complex (4tfmppy)Pt(dptp) with 6 wt% doped concentration shows superior performances with a maximum EQE of 26.90% with mild efficiency roll-off. This study demonstrates that the ancillary ligand attached with a 4-phenyl-4H-1,2,4-triazole group could facilitate charge trapping across the bulk of the device for efficient OLEDs.

10.
Chemistry ; 25(22): 5623-5642, 2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-30648301

RESUMO

Thermally activated delayed fluorescence (TADF) is one of the most intriguing and promising discoveries towards realization of highly-efficient organic light emitting diodes (OLED) utilizing small molecules as emitters. It has the capability of manifesting all excitons generated during the electroluminescent processes, consequently achieving 100 % of internal quantum efficiency. Since the report of the first efficient OLED based on a TADF small molecule in 2012 by Adachi et al., the quest for optimal TADF materials for OLED application has never stopped. Various TADF molecules bearing different design concepts and strategies have been designed and produced, with the aim to boost the overall performances of corresponding OLEDs. In this minireview, the general principles of TADF molecular design based on three basic categories of TADF species: twisted intramolecular charge transfer (TICT), through-space charge transfer (TSCT) and multi-resonance induced TADF (MR-TADF) are discussed in detail. Several key aspects with respect to each category, as well as some effective methods to enhance the efficiency of TADF materials and corresponding OLEDs from the molecular engineering perspectives, are summarized and discussed to exhibit a general landscape of TADF molecular design to a wide variety of scientific researchers within this particular disciplinary area.

11.
Dalton Trans ; 47(46): 16543-16550, 2018 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-30412209

RESUMO

Aiming to balance the injection and transport of electrons and holes, nitrogen heterocycle and 1,3,4-oxadiazole derivatives were introduced in iridium(iii) complexes to obtain organic light-emitting diodes (OLEDs) with high performances. Thus, two novel Ir(iii) complexes (Ir(tfmphpm)2(pop) and Ir(tfmppm)2(pop)) with green emissions using 2-(3,5-bis(trifluoromethyl)phenyl)pyrimidine (tfmphpm) and 2-(2,6-bis(trifluoromethyl)pyridin-4-yl)pyrimidine (tfmppm) as cyclometalating ligands, and 2-(5-phenyl-1,3,4-oxadiazol-2-yl)phenol (pop) as an ancillary ligand were synthesized. Both emitters show high photoluminescence efficiencies up to 94% and good electron mobility. The devices using two emitters with the structure of ITO (indium-tin-oxide)/MoO3 (molybdenum oxide, 5 nm)/TAPC (di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane, 30 nm)/mCP (1,3-bis(9H-carbazol-9-yl)benzene, 5 nm)/Ir(iii) complexes (6 wt%) : PPO21 (3-(diphenylphosphoryl)-9-(4-(diphenylphosphoryl)phenyl)-9H-carbazole, 10 nm)/TmPyPB (1,3,5-tri(m-pyrid-3-yl-phenyl) benzene, 40 nm)/LiF (1 nm)/Al (100 nm) display good electroluminescence performances with a maximum luminance of 48 981 cd m-2, a maximum current efficiency of 92.79 cd A-1 and a maximum external quantum efficiency up to 31.8%, respectively, and the efficiency roll-off ratio is low, suggesting that they have potential application in OLEDs.

12.
Angew Chem Int Ed Engl ; 57(35): 11316-11320, 2018 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-29974588

RESUMO

Multi-resonance induced by boron and nitrogen atoms in opposite resonance positions endows a thermally activated delayed fluorescence (MR-TADF) emitter with a strikingly small full width at half maximum of only 26 nm and excellent photoluminescence quantum yield of up to 97.48 %. The introduction of a carbazole unit in the para position of the B-substituted phenyl-ring can significantly boost up the resonance effect without compromising the color fidelity, subsequently enhancing the performances of the corresponding pure blue TADF-OLED, with an outstanding external quantum efficiency (EQE) up to 32.1 % and low efficiency roll-off, making it one of the best TADF-OLEDs in the blue region to date. Furthermore, utilizing this material as host for a yellow phosphorescent emitter, the device also shows a significantly reduced turn-on voltage of 3.2 V and an EQEmax of 22.2 %.

13.
Dalton Trans ; 47(24): 8032-8040, 2018 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-29872814

RESUMO

Four bis-cyclometalated iridium(iii) complexes, (bt)2Ir(tpip), (fbt)2Ir(tpip), (cf3bt)2Ir(tpip) and (dfbt)2Ir(tpip) (bt = 2-phenylbenzo[d]thiazole, fbt = 6-fluoro-2-phenylbenzo[d]thiazole, cf3bt = 2-phenyl-6-(trifluoromethyl)benzo[d]thiazole, dfbt = 5,7-difluoro-2-phenylbenzo[d]thiazole, tpip = tetraphenylimidodiphosphinate) have been synthesized and investigated. All complexes emit yellow light peaks at 564-574 nm with quantum efficiencies (Φem) of 27.1-48.4% and excited state lifetimes of 2.40-2.81 µs in degassed CH2Cl2 solution at room temperature. Correspondingly, organic light-emitting diodes (OLEDs) using these complexes as emitters achieve yellow electrophosphorescence with good device characteristics. Due to its highest photoluminescence quantum yield (48.4%), the device based on (dfbt)2Ir(tpip) displays the best device performance with a maximum current efficiency (ηc, max) of up to 69.8 cd A-1 and a maximum external quantum efficiency (EQEmax) of up to 24.3%. Furthermore, all devices showed low efficiency roll-off ratios. The EQE could still be retained at 17.7%, 16.4%, 18.3% and 20.6% for four devices at a luminance of 1000 cd m-2. These results suggest that these materials have potential application in efficient OLEDs.


Assuntos
Benzotiazóis/química , Complexos de Coordenação/química , Irídio/química , Eletroquímica , Ligantes , Luminescência
14.
Dalton Trans ; 47(22): 7587-7593, 2018 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-29790538

RESUMO

Two novel iridium(iii) complexes Ir(BTBP)2mepzpy and Ir(BTBP)2phpzpy were successfully synthesized, in which 2',6'-bis(trifluoromethyl)-2,4'-bipyridine (BTBP) was used as the main ligand, and 2-(3-methyl-1H-pyrazol-5-yl)pyridine (mepzpy) and 2-(3-2-(3-phenyl-1H-pyrazol-5-yl))pyridine (phpzpy) were introduced as the ancillary ligands, respectively. Both Ir(iii) complexes displayed bluish green emission peaks at 486 and 487 nm with high quantum efficiencies of 0.73 and 0.69, respectively. The organic light-emitting diodes (OLEDs) with the structure of ITO/HATCN (hexaazatriphenylenehexacarbonitrile, 5 nm)/TAPC (bis[4-(N,N-ditolylamino)-phenyl]cyclohexane, 40 nm)/Ir(BTBP)2mepzpy or Ir(BTBP)2phpzpy (10 wt%): 2,6-DCzPPy (2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine, 10 nm)/TmPyPB (1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene, 30 nm)/LiF (1 nm)/Al (100 nm) exhibited high efficiencies with low efficiency roll-off. Especially, the device based on the Ir(BTBP)2mepzpy complex achieved a maximum current efficiency of 58.17 cd A-1 and a maximum external quantum efficiency of 25.33% with Commission Internationale de 1'Eclairage coordinates of (0.19, 0.43). These results indicate that novel cyclometalated Ir(iii) complexes for high efficiency OLEDs with low efficiency roll-off were obtained by our rational design.

15.
Dalton Trans ; 47(12): 4045-4048, 2018 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-29479610

RESUMO

Four novel chiral iridium(iii) complexes with triplex stereogenic centers were synthesized by introducing chiral carbon atoms into cyclometalated and ancillary ligands, and separated into eight isomers, which coincide with the old Chinese philosophy Eight Trigrams. The electron circular dichroism and circularly polarized luminescence spectra of four pairs of isomers show perfect mirror images with a dissymmetry factor (glum factor) of around 0.003.

16.
Dalton Trans ; 46(43): 14916-14925, 2017 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-29043334

RESUMO

Two novel iridium(iii) complexes, Ir(tfmpiq)2(acac) (tfmpiq = 1-(2,6-bis(trifluoromethyl)pyridin-4-yl)isoquinoline, acac = acetylacetone) and Ir(tfmpqz)2(acac) (tfmpqz = 4-(2,6-bis(trifluoromethyl)pyridin-4-yl)quinazoline), were synthesized and thoroughly investigated. Both complexes emit orange-red photoluminescence with high quantum yields (Ir(tfmpiq)2(acac): λmax: 587 nm, ηPL: 42%; Ir(tfmpqz)2(acac): λmax: 588 nm, ηPL: 91%). Furthermore, the complex containing quinazoline shows higher electron mobility than that with isoquinoline. The organic light-emitting diodes (OLEDs) with single- or double-emitting layers (EML) were fabricated using two new emitters. The double-EML device using Ir(tfmpqz)2(acac) with the structure of ITO (indium-tin-oxide)/MoO3 (molybdenum oxide, 3 nm)/TAPC (di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane, 50 nm)/Ir(tfmpqz)2(acac) (1 wt%):TcTa (4,4',4''-tris(carbazole-9-yl)triphenylamine, 10 nm)/Ir(tfmpqz)2(acac) (1 wt%):2,6DCzPPy (2,6-bis(3-(carbazol-9-yl)phenyl)pyridine, 10 nm)/TmPyPB (1,3,5-tri(m-pyrid-3-yl-phenyl)benzene, 50 nm)/LiF (1 nm)/Al (100 nm) displays good electroluminescence performances with a maximum luminance of 96 609 cd m-2, a maximum current efficiency of 59.09 cd A-1, a maximum external quantum efficiency of 20.2%, a maximum power efficiency of 53.61 lm W-1, and the efficiency roll-off ratio is mild.

17.
Chem Commun (Camb) ; 53(49): 6637-6640, 2017 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-28585623

RESUMO

On account of the broad utilities of organophosphorus compounds, the development of highly efficient and concise phosphination methods is significantly important and urgent. Herein, we disclose a novel method for the synthesis of phosphorylated heterocycles: versatile intermediate propargylamines serving as a new type of radical acceptors incorporated in P-radicals via a photocatalytic strategy. This reaction proceeds through a cascade phosphinoylation/cyclization/oxidation/aromatization pathway using readily available starting materials under mild conditions of light with excellent atom economy, catalyzed by AgOAc or fac-Ir(ppy)3. One of the phosphorylated quinolines was selected, as an example, as an electron-transporting material for fabricating phosphorescence organic light-emitting diodes displaying excellent electroluminescence performances with a maximum external quantum efficiency of 21.9% with negligible efficiency roll-off ratios.

18.
Dalton Trans ; 46(3): 845-853, 2017 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-28001164

RESUMO

Using 2',6'-bis(trifluoromethyl)-2,4'-bipyridine as a monoanionic cyclometalated ligand, 2-(5-(4-(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)phenol and 2-(5-(4-(trifluoromethyl) phenyl)-1,3,4-thiadiazol-2-yl)phenol as ancillary ligands, two new heteroleptic iridium(iii) complexes (Ir1 and Ir2) were prepared and investigated. The ancillary ligand variations affected their emissions greatly, and the complexes Ir1 and Ir2 emitted green (503 nm) and orange (579 nm) lights, respectively. Moreover, the electron mobility of the two complexes is as high as that of the electron transport material Alq3 (tris-(8-hydroxyquinoline)aluminium), which is useful for their performances in organic light-emitting diodes (OLEDs). The OLEDs with Ir1 as the emitter showed excellent performances with a maximum current efficiency of 74.8 cd A-1, a maximum external quantum efficiency of 27.0%, a maximum power efficiency of 33.4 lm W-1, and the efficiency roll-off is mild. These results suggest that complexes with 1,3,4-oxadiazole/1,3,4-thiadiazole derivatives have potential application as efficient emitters in OLEDs.

19.
Sci Rep ; 6: 38478, 2016 12 08.
Artigo em Inglês | MEDLINE | ID: mdl-27929124

RESUMO

Due to the high quantum efficiency and wide scope of emission colors, iridium (Ir) (III) complexes have been widely applied as guest materials for OLEDs (organic light-emitting diodes). Contrary to well-developed Ir(III)-based red and green phosphorescent complexes, the efficient blue emitters are rare reported. Like the development of the LED, the absence of efficient and stable blue materials hinders the widely practical application of the OLEDs. Inspired by this, we designed two novel ancillary ligands of phenyl(pyridin-2-yl)phosphinate (ppp) and dipyridinylphosphinate (dpp) for efficient blue phosphorescent iridium complexes (dfppy)2Ir(ppp) and (dfppy)2Ir(dpp) (dfppy = 2-(2,4-difluorophenyl)pyridine) with good electron transport property. The devices using the new iridium phosphors display excellent electroluminescence (EL) performances with a peak current efficiency of 58.78 cd/A, a maximum external quantum efficiency of 28.3%, a peak power efficiency of 52.74 lm/W and negligible efficiency roll-off ratios. The results demonstrated that iridium complexes with pyridinylphosphinate ligands are potential blue phosphorescent materials for OLEDs.

20.
Dalton Trans ; 46(1): 150-157, 2016 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-27901155

RESUMO

Two new platinum(ii) cyclometalated complexes with 2-(4-trifluoromethyl)phenylpyridine (4-tfmppy) as the main ligand and tetraphenylimidodiphosphinate (tpip) (Pt-tpip) and tetra(4-fluorophenyl)imidodiphosphinate (ftpip) (Pt-ftpip) as ancillary ligands were developed. Both complexes were green phosphors with photoluminescence quantum efficiency yields of 71.5% and 79.2% in CH2Cl2 solution at room temperature, respectively. The organic light-emitting diodes with a double emissive layers structure of ITO/TAPC (1,1-bis(4-(di-p-tolylamino)phenyl)cyclohexane), 40 nm/Pt-tpip or Pt-ftpip: TcTa (4,4',4''-tri(9-carbazoyl)-triphenylamine) (5 wt%, 10 nm)/Pt-tpip or Pt-ftpip: 2,6DCzPPy (2,6-bis(3-(carbazol-9-yl)phenyl)pyridine) (5 wt%, 10 nm)/TmPyPB (1,3,5-tri(m-pyrid-3-yl-phenyl)benzene, 40 nm)/LiF (1 nm)/Al (100 nm) showed good performances. In particular, the device based on the Pt-ftpip complex with a 5 wt% doped concentration showed superior performance with a low drive voltage of 3.3 V, a maximum current efficiency of 48.3 cd A-1, a maximum external quantum efficiency of 14.0%, and a maximum power efficiency of 35.7 lm W-1, respectively. Even at a brightness of 1000 cd m-2, a current efficiency of 47.0 cd A-1 could still be obtained, suggesting that the ancillary ligands (tpip and ftpip) can be employed well in Pt(ii) complexes, which could find potential applications in OLEDs.

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