Os(II) Based Green to Red Phosphors: A Great Prospect for Solution‐Processed, Highly Efficient Organic Light‐Emitting Diodes

Du, Bo-Sian; Liao, Jia-Ling; Huang, Meei-Feng; Lin, Chih‐Hsun; Lin, Hao‐Wu; Chi, Yun; Pan, Hsiao‐An; Fan, Gang-Lun; Wong, Ken‐Tsung; Lee, Gene‐Hsiang; Chou, Pi‐Tai

doi:10.1002/adfm.201200718

Cited by 98 publications

(43 citation statements)

References 67 publications

(29 reference statements)

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“…However, TADF-FlOLED is expected to suffer from unstable efficiencies with driving voltages and temperatures. Thus, phosphorescent OLEDs (PhOLEDs) still dominate high efficiency devices [6][7][8] because of the 100% theoretical IQE [9,10].…”

Section: Introductionmentioning

confidence: 99%

Influences of fluorination on homoleptic iridium complexes with C∧N=N type ligand to material properties, ligand orientation and OLED performances

et al. 2014

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Two new iridium complexes with C^N=N type ligand (i.e., Ir(BFPPya) 3 {tris[3,6-bis(4-fluorophenyl)pyridazine]iridium(III)} and Ir(BDFPPya) 3 {tris[3,6-bis (2,4-di-fluorophenyl)pyridazine]iridium(III)}) attaching with fluorine atoms, were synthesized and the effects of fluorination on the material properties and device performance were investigated. Compared with our previously reported fluorine-free analogue material, that is Ir(BPPya) 3 {tris[3,6-bis(phenyl)pyridazine]iridium(III)}, blue shifts in the emission spectra as well as in the long wavelength region of the absorptions were observed. The photoluminescence quantum yield (PLQY) (0.44 and 0.84 vs 0.29), phosphoresces lifetime (0.88 and 1.31 vs 0.66 s), and oxidation potential (1.10 and 1.37 vs 0.95 V) increased obviously after fluorinating the ligand. In contrast, the thermal stability of the iridium complexes decreased slightly (Td: 435 and 402 vs 440 °C). In the density functional theory (DFT) calculations, by comparing the steric shape of the three ligands within one optimized molecule, orientational differences among the complexes were observed. In OLED device studies, bluish green electroluminescence with peak emission of 500 nm, using the electron-transporting host of TPBI [2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)] and the most fluorinated dopant of Ir(BDFPPya) 3 , was achieved with maximum efficiency of 20.3 cd/A. On one hand this efficiency is not satisfactory considering a high PLQY of 0.84. On the other hand with the similar device structure, that the (HOMO-LUMO)s of all the dopants are wrapped within that of the host TPBI, and all the triplet energies of the dopants are smaller than that of the host TPBI, it is abnormal that the ordering of device efficiencies is contradictory to that of PLQY. Assisting with the phosphorescent spectrum of TPBI and the absorption spectra of the dopant, the contradiction was interpreted reasonably.

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Section: Introductionmentioning

confidence: 99%

Influences of fluorination on homoleptic iridium complexes with C∧N=N type ligand to material properties, ligand orientation and OLED performances

et al. 2014

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“…[3] In fluorescent OLEDs, radiative decay of the 75 %t riplet excitons is spin-forbidden and only the 25 %s inglet excitonsl uminesce,w hereas phosphorescent OLEDs can facilitate the singlet-triplet mixingb ye ffective spin-orbit coupling, harvest both singleta nd triplet excitons, thus achieve near-unity internalq uantum efficiency (IQE). [6][7][8][9][10][11][12][13] Neutral complexes of ruthenium(II), [14][15][16] osmium(II), [17][18][19][20] iridium(III), [21][22][23][24][25][26][27] and platinum(II) [4,[28][29][30][31][32][33][34] have been rapidlyd eveloped and widely employed as phosphorescent dopants for polychromic OLEDs. [6][7][8][9][10][11][12][13] Neutral complexes of ruthenium(II), [14][15][16] osmium(II), [17][18][19][20] iridium(III), …”

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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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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“…As can be seen, all three TFOS sensitizers showed dual MLCT transitions at % 425 and 510 nm, and with molar absorption coefficients greater than 1.1 10 4 mol À1 cm À1 , which were more-orless comparable to the MLCT bands observed in the N719 reference sensitizer. [16] Furthermore, the red-shifting of 3 MLCT absorption for TFOS-2 versus TFOS-1 was clearly attributed to the electron-donating effect of the tert-butyl substituent, which destabilized the HOMO localized at the Os II metal. We attributed this broad peak to the spin-forbidden 3 MLCT absorption, for which the increased absorptivity was clearly the result of enhanced spin-orbit coupling, induced by the heavy-atom effect of the Os II core.…”

Section: Photophysical and Electrochemical Propertiesmentioning

confidence: 97%

Design of Os^II‐based Sensitizers for Dye‐Sensitized Solar Cells: Influence of Heterocyclic Ancillaries

Hu¹,

Wang²,

Planells³

et al. 2013

ChemSusChem

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A series of Os(II) sensitizers (TFOS-x, in which x=1, 2, or 3) with a single 4,4'-dicarboxy-2,2'-dipyridine (H2 dcbpy) anchor and two chelating 2-pyridyl (or 2-pyrimidyl) triazolate ancillaries was successfully prepared. Single-crystal X-ray structural analysis showed that the core geometry of the Os(II) -based sensitizers consisted of one H2 dcbpy unit and two eclipsed cis-triazolate fragments; this was notably different from the Ru(II) -based counterparts, in which the azolate (both pyrazolate and triazolate) fragments are located at the mutual trans-positions. The basic properties were extensively probed by using spectroscopic and electrochemical methods as well as time-dependent density functional theory (TD-DFT) calculations. Fabrication of dye-sensitized solar cells (DSCs) was then attempted by using the I(-) /I3 (-) -based electrolyte solution. One such DSC device, which utilized TFOS-2 as the sensitizer, showed promising performance characteristics with a short-circuit current density (JSC ) of 15.7 mA cm(-2) , an open-circuit voltage of 610 mV, a fill factor of 0.63, and a power conversion efficiency of 6.08 % under AM 1.5G simulated one-sun irradiation. Importantly, adequate incident photon-to-current conversion efficiency performances were observed for all TFOS derivatives over the wide spectral region of 450 to 950 nm, showing a panchromatic light harvesting capability that extended into the near-infrared regime. Our results underlined a feasible strategy for maximizing JSC and increasing the efficiency of DSCs.

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Os(II) Based Green to Red Phosphors: A Great Prospect for Solution‐Processed, Highly Efficient Organic Light‐Emitting Diodes

Cited by 98 publications

References 67 publications

Influences of fluorination on homoleptic iridium complexes with C∧N=N type ligand to material properties, ligand orientation and OLED performances

Influences of fluorination on homoleptic iridium complexes with C∧N=N type ligand to material properties, ligand orientation and OLED performances

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

Design of Os^II‐based Sensitizers for Dye‐Sensitized Solar Cells: Influence of Heterocyclic Ancillaries

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Os(II) Based Green to Red Phosphors: A Great Prospect for Solution‐Processed, Highly Efficient Organic Light‐Emitting Diodes

Cited by 98 publications

References 67 publications

Influences of fluorination on homoleptic iridium complexes with C∧N=N type ligand to material properties, ligand orientation and OLED performances

Influences of fluorination on homoleptic iridium complexes with C∧N=N type ligand to material properties, ligand orientation and OLED performances

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

Design of OsII‐based Sensitizers for Dye‐Sensitized Solar Cells: Influence of Heterocyclic Ancillaries

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Design of Os^II‐based Sensitizers for Dye‐Sensitized Solar Cells: Influence of Heterocyclic Ancillaries