Endothermic energy transfer: A mechanism for generating very efficient high-energy phosphorescent emission in organic materials

Adachi, Chihaya; Kwong, Raymond C.; Djurovich, Peter; Adamovich, Vadim; Baldo, Marc A.; Thompson, Mark E.; Forrest, Stephen R.

doi:10.1063/1.1400076

Cited by 1,046 publications

(700 citation statements)

References 11 publications

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“…The quantum yields of solutions of 1 and 2 were measured using FIrpic (0.6) as a reference. 18 Compound 1 showed Φ PL values in the range of 60-28%, whereas compound 2 showed Φ PL values of 70, 67, and 59% at each concentration, as shown in Figure 5. The decrease in emission of compound 1 compared with compound 2 was promoted at high concentration.…”

Section: Mlctmentioning

confidence: 99%

Homoleptic Iridium(III) Compounds Bearing Bulky Bipyridine Ligand for Potential Application to Organic Light‐emitting Diodes

Kim

Park

et al. 2017

Bulletin Korean Chem Soc

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Two sky-blue phosphorescent iridium compounds, fac-tris(2 0 ,6 0 -diisopropoxy-2,3 0 -bipyridinato)-N,C 4 )Ir (III) (1) and fac-tris(2 0 ,6 0 -diisopropoxy-4-tert-butyl-2,3 0 -bipyridinato)-N,C 4 )Ir(III) (2), were synthesized by a one-pot reaction of a reactive Ir(I) compound with a corresponding bipyridine ligand, to investigate their photophysical and electrochemical properties for potential application to white organic light-emitting diodes (WOLEDs). Their structures were confirmed by varied spectroscopic methods. Results indicated that both compounds possess facial geometry. The absorption, emission, thermal stability, and electrochemical properties were also investigated systematically. The two compounds showed sky-blue emission with λ max = 462-463 nm; their photoluminescence quantum efficiencies relative to that of FIrpic werẽ 0.3-0.4. Compound 2 with a bulky substituent displayed the suppression of concentration quenching at high concentration, and its emission was less shifted to longer wavelengths compared to compound 1. Owing to the bulky substituent, the quantum efficiency of 2 is higher than that of its nonsubstituted counterpart. Therefore, the introduction of the bulky substituent in the ligand framework is an important strategy for developing high-efficiency blue phosphorescent materials. The two compounds developed in this study show high thermal and electrochemical stability, making them suitable candidates for OLED applications.

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Section: Mlctmentioning

confidence: 99%

Homoleptic Iridium(III) Compounds Bearing Bulky Bipyridine Ligand for Potential Application to Organic Light‐emitting Diodes

Kim

Park

et al. 2017

Bulletin Korean Chem Soc

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“…27 Its is ϳ1 s, and its emission peaks at ϳ470 nm, i.e., close to that of the fluorescent material DPVBi. We therefore fabricated Firpic-based OLEDs as well, with the structure Glass/͓150 nm ITO͔/͓5nm CuPc͔/͓35 nm NPD͔/͓50, 60, 70, and 80 nm FIrpic-doped CBP͔/͓30 nm BCP͔/͓6 nm Alq 3 ͔/͓1 nm CsF͔/Al.…”

Section: El Decay Time Measurements Of Phosphorescent Oledmentioning

confidence: 99%

Spectrally narrowed edge emission from leaky waveguide modes in organic light-emitting diodes

Gan

Tian

Lynch

et al. 2009

Journal of Applied Physics

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A dramatic spectral line narrowing of the edge emission at room temperature from tris(quinolinolate) Al (Alq3), N,N′-diphenyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine (NPD), 4,4′-bis(2,2′-diphenyl-vinyl)-,1′-biphenyl (DPVBi), and some guest-host small molecular organic light-emitting diodes(OLEDs), fabricated on indium tin oxide (ITO)-coated glass, is described. In all but the DPVBi OLEDs, the narrowed emission band emerges above a threshold thickness of the emitting layer, and narrows down to a full width at half maximum of only 5-10 nm. The results demonstrate that this narrowed emission is due to irregular waveguide modes that leak from the ITO to the glass substrate at a grazing angle. While measurements of variable stripe length l devices exhibit an apparent weak optical gain 0≤g≤1.86 cm−1, there is no observable threshold current or bias associated with this spectral narrowing. In addition, in the phosphorescent guest-host OLEDs, there is no decrease in the emission decay time of the narrowed edge emission relative to the broad surface emission. It is suspected that the apparent weak optical gain is due to misalignment of the axis of the waveguided mode and the axis of the collection lens of the probe. However, it is not clear if such a misalignment can account for all the effects of the observed evolution of the edgeemission spectra with l. KeywordsAmes Laboratory, Organic light emitting diodes, Glass waveguides, Spontaneous emission, Cathodes, Emission spectra A dramatic spectral line narrowing of the edge emission at room temperature from tris͑quinolinolate͒ Al ͑Alq 3 ͒, N , , 4Ј-diamine ͑NPD͒, 4,4Ј-bis͑2,2Ј-diphenyl-vinyl͒-,1Ј-biphenyl ͑DPVBi͒, and some guest-host small molecular organic light-emitting diodes ͑OLEDs͒, fabricated on indium tin oxide ͑ITO͒-coated glass, is described. In all but the DPVBi OLEDs, the narrowed emission band emerges above a threshold thickness of the emitting layer, and narrows down to a full width at half maximum of only 5-10 nm. The results demonstrate that this narrowed emission is due to irregular waveguide modes that leak from the ITO to the glass substrate at a grazing angle. While measurements of variable stripe length l devices exhibit an apparent weak optical gain 0 Յ g Յ 1.86 cm −1 , there is no observable threshold current or bias associated with this spectral narrowing. In addition, in the phosphorescent guest-host OLEDs, there is no decrease in the emission decay time of the narrowed edge emission relative to the broad surface emission. It is suspected that the apparent weak optical gain is due to misalignment of the axis of the waveguided mode and the axis of the collection lens of the probe. However, it is not clear if such a misalignment can account for all the effects of the observed evolution of the edge-emission spectra with l.

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“…[4][5][6][7] In the case of iTMC, the fabrication consist in the deposition of a single layer of the iTMC material by spin coating onto ITO (Indium Tin Oxide) followed by a metallic cathode deposited by evaporation under vacuum. 8 In the case of the OLED devices, the fabrication consists in a multilayer architecture, including the emitter layer (neutral molecule or polymer), sandwiched between two electrodes. Organic layers are added to promote the electron and hole injection into the light emissive layer.…”

Section: Introductionmentioning

confidence: 99%

ANOMALOUS BEHAVIOR OF Ir(III) CYCLOMETALATED COMPLEXES: APPLICATION IN LIGHT-EMITTING ELECTROCHEMICAL CELLS

Dreyse

Loeb

Barrera

et al. 2014

J. Chil. Chem. Soc.

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The cationic Ir(III) complex with 7,8-benzoquinoline (bzq) as cyclometalating ligand and 4,4´-diterbutyl-2,2´-bipyridine (tBuB) as ancillary ligand, [Ir(bzq) 2 (tBuB)](PF 6 ) (1), was utilized in the fabrication of a light-emitting electrochemical cell (LEC). The photophysical properties and the characterization of the LEC device with this complex was compared with literature data for the analogous complex with 2-phenylpyridine (ppy), [Ir(ppy) 2 (tBuB)](PF 6 ) (2). Complex 1 showed blue shifted emission compared to complex 2. Surprisingly, complex 1 shows lower luminance, efficiency and stability in regard to 2. This behavior correlated well with the low values of quantum yield and lifetime, registered for complex 1 in solution. The performance observed is unexpected, taking into account the emission wavelengths recorded for each complex, and the lesser non radiative deactivation processes expected for a complex with a more rigid ligand as bzq. A possible explanation of this behavior is given in terms of the predominance of a fluorescent emission in the case of the complex 1 instead of a phosphorescent emission, as observed for complex 2.

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Endothermic energy transfer: A mechanism for generating very efficient high-energy phosphorescent emission in organic materials

Cited by 1,046 publications

References 11 publications

Homoleptic Iridium(III) Compounds Bearing Bulky Bipyridine Ligand for Potential Application to Organic Light‐emitting Diodes

Homoleptic Iridium(III) Compounds Bearing Bulky Bipyridine Ligand for Potential Application to Organic Light‐emitting Diodes

Spectrally narrowed edge emission from leaky waveguide modes in organic light-emitting diodes

ANOMALOUS BEHAVIOR OF Ir(III) CYCLOMETALATED COMPLEXES: APPLICATION IN LIGHT-EMITTING ELECTROCHEMICAL CELLS

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