High-performance fluorescent/phosphorescent (F/P) hybrid white OLEDs consisting of a yellowish-green phosphorescent emitter

Du, Xiaoyang; Zhao, Juewen; Yuan, Shaolin; Zheng, Caijun; Lin, Hui; Lee, Chun‐Sing

doi:10.1039/c6tc01421f

Cited by 38 publications

(19 citation statements)

References 57 publications

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“…To fulfill this requirement, 4,4′-bis(N-carbazolyl)biphenyl (CBP) and tris(2-phenylpyridine) iridium (Ir(ppy)3) were used as the host and trap material, respectively. The HOMO levels of CBP and Ir(ppy)3 are 6.0 eV and 5.6 eV, respectively (13), such that the difference in their HOMO levels is substantially larger than the thermal energy at room temperature. Thus, Ir(ppy)3 within CBP may act as the deep hole traps.…”

Section: Resultsmentioning

confidence: 99%

69‐1: Invited Paper: Trap‐dependent Electrical Characteristics of Organic Semiconductor Devices

Lee

2020

Symp Digest of Tech Papers

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Trap states strongly affect the electrical characteristics of organic semiconductor devices. Here, we report how the spatial distribution of the traps affects the current density-voltage (J-V) characteristics of single-charge carrier devices. We found that when the traps are located near a charge-injecting electrode, the electric field and thus the operating voltage of a device increase, leading to an increased device resistivity. We analyzed the J-V characteristics vs. position of the traps by assuming that the devices are space-charge-limited and the energy levels of the traps follow a Gaussian distribution.

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Section: Resultsmentioning

confidence: 99%

69‐1: Invited Paper: Trap‐dependent Electrical Characteristics of Organic Semiconductor Devices

Lee

2020

Symp Digest of Tech Papers

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“…For all compounds, the first two triplets (i.e., T 1 and T 2 ) are centered on the benzoxazole-based ancillary ligand, while T 3 and T 4 mainly involve the two cyclometalating phenylpyridine ligands (see SI, Tables S4. [1][2][3][4][5][6].…”

Section: Lowest-lying Triplet Statesmentioning

confidence: 99%

“…Cyclometalated iridium(III) complexes displaying sizeable phosphorescence emission have been the focus of intense research due to their strategic position at the crossroad of many attractive applications. These phosphorescent emitters have been indeed beneficially used in applicative fields including optoelectronics, [1][2][3][4][5] non-linear optics, [6] sensing, [7][8][9][10] or as particularly biocompatible probes for in vitro bioimaging. [11][12][13] This interest is largely due to the possibility to fine-tune their photophysical properties depending on subtle electronic modifications on the π-conjugated backbone of the ligands coordinated to the metal.…”

Section: Introductionmentioning

confidence: 99%

Phosphorescent Cyclometalated Iridium(III) Complexes Bearing Ethynyl‐Extended 2‐(2'‐Hydroxyphenyl) Benzoxazole Ancillary Ligands

et al. 2020

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This article describes the synthesis and full photophysical studies at room and low temperature of a series of iridium(III) complexes incorporating an ethynyl-extended benzoxazole-based ancillary ligand. The electronic nature of the terminal end-group of the ancillary ligand was modulated by the simple introduction of electron-donating (Me, NBu 2 ) or -withdrawing (CN) groups. For all complexes, TD-DFT calculations showed that the lowest-lying transition was ligand-centered [a] Dr.Scheme 2. Synthesis of cyclometalated iridium(III) complexes 4-6 and 7-9. Results and Discussion SynthesisThe synthesis of the cyclometalated iridium(III) complexes 4-6 and 7-9 is presented on Scheme 2. The synthetic targets can be obtained straightforwardly in one step, starting from the previously reported 2-(2′-hydroxyphenyl)benzoxazole (HBO) ligands 1-3, [29] respectively functionalized by p-ethynyl-tolyl (R = Me), p-ethynyl-phenyl-N-dibutylamino (R = NBu 2 ) or p-ethynylbenzonitrile (R = CN) groups. The formation of the targeted cyclometalated iridium(III) complexes can be readily achieved by reacting the iridium(III) chloro-bridged dimers precursors A or B with two equivalents of HBO chelates 1-3, in the presence of an excess of potassium carbonate in a mixture of methanol and dichloromethane at 40°C (Scheme 2). Pure iridium(III) complexes were obtained in 47-72 % yield after purification on a silica gel column chromatography. All dimers were characterized with 1 H-NMR spectroscopy and high-resolution mass spectrometry (HR-MS), reflecting their molecular structure in each case. Formation of the targeted complexes 4-6 and 7-9 was notably confirmed by assessing the disappearance of the downfield H-bonded phenolic proton present in the molecular structure of starting HBO ligands 1-3 by 1 H-NMR spectroscopy. All spectra can be found in the Supporting Information (SI). As reported for other similar Ir (III) cyclometalated complexes, it is expected that complexes 4-9 adopt a distorted octahedral geometry with the nitrogen atoms of the pyridine moiety in trans position. [30] Absorption Absorption spectra of HBO ligands 1-3 and iridium(III) heteroleptic complexes 4-9, recorded in acetonitrile solution at room column chromatography on SiO 2 eluting with CH 2 Cl 2 /pet. ether to yield complexes 4-9 as yellow powders in 47-72 % yield. Complex 4: Yellow powder. 58 %. 1 H-NMR (400 MHz, CDCl 3 ) δ (ppm) = 8.74 (d, 1H, CH Ar, J = 5.2 Hz), 8.14 (d, 1H, CH Ar, J = 2.4 Hz), 8.02 (d, 1H, CH Ar, J = 5.6 Hz), 7.79 (d, 1H, CH Ar, J = 8 Hz), 7.72 (d, 1H, CH Ar, J = 8 Hz), 7.51-7.60 (m, 4H, CH Ar), 7.37 (d, 1H, CH Ar, J = 8 Hz), 7.32 (d, 2H, CH Ar, J = 8 Hz), 7.23 (dd, 1H, CH Ar, J = 9 Hz), 7.05-7.08 (m, 3H, CH Ar), 6.97 (t, 1H, CH Ar, J = 6 Hz), 6.68-6.87 (m, 6H, CH Ar), 6.62 (d, 1H, CH Ar, J = 9.2 Hz), 6.40 (d, 1H, CH Ar, J = 7.6 Hz), 6.11 (d, 1H, CH Ar, J = 7.6 Hz), 6.01 (d, 1H, CH Ar, J = 8.4 Hz), 2.28 (s, 3H, CH 3 ). ESI-HRMS: calcd. for C 44 H 31 IrN 3 O 2 [M + H] 826.2043, found [M + H] 826.2052. Complex 5: Yellow powder. 72 %. 1 H-NMR (400 MHz, ...

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“…However, this design would limit the harvesting of excitons for radiative decay due to the nature of traditional fluorescent dye, and enhance the difficulty of designing efficient WOLEDs. [11][12][13] Recently, thermally delayed activated fluorescence (TADF) materials including intermolecular or intramolecular charge transferred materials have aroused much research interest. [3,5,[14][15][16][17] Since the bandgap between the singlet and triplet energy levels is sufficiently small in TADF dyes, triplet excitons can be efficiently up converted to the singlet state through a reverse intersystem crossing (RISC) process in a way that the TADF emitters can harvest nonradiative triplet excitons.…”

Section: Introductionmentioning

confidence: 99%

Hybrid Tandem White OLED with Long Lifetime and 150 Lm W⁻¹ in Luminous Efficacy Based on TADF Blue Emitter Stabilized with Phosphorescent Red Emitter

Huang

Zhang

Zhou

et al. 2020

Advanced Optical Materials

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Modern lighting requires high efficiency and long lifetime simultaneously. In this paper, highly efficient white organic light emitting diodes (WOLEDs) are demonstrated based on a modified hybrid tandem structure constructed with a phosphorescent yellow‐red unit using an exciplex host and a blue‐red unit based on a thermally activated delayed fluorescence (TADF) blue emitter, and the devices are properly built with internal and external light extraction structures. The resulting four‐color WOLED exhibits an external quantum efficiency and luminous efficacy of 126.2% and 150.7 Lm W−1, respectively, and the color rendering index is close to 80 at a brightness of 1000 cd m−2. This device also shows a very good color stability with increasing luminance up to 15 000 cd m−2 and there is only a small angular color variation for viewing angles changing from 0° to 70°. The T50 lifetime (defined as the time corresponding to 50% decrease in luminance from an initial value) of the WOLED at an initial luminance of 1000 cd m−2 is extrapolated as 12 600 h.

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High-performance fluorescent/phosphorescent (F/P) hybrid white OLEDs consisting of a yellowish-green phosphorescent emitter

Abstract: F/P WOLEDs with a high luminous efficiency and a high color rending index have been achieved by employing a yellowish green emitter.

Cited by 38 publications

References 57 publications

69‐1: Invited Paper: Trap‐dependent Electrical Characteristics of Organic Semiconductor Devices

69‐1: Invited Paper: Trap‐dependent Electrical Characteristics of Organic Semiconductor Devices

Phosphorescent Cyclometalated Iridium(III) Complexes Bearing Ethynyl‐Extended 2‐(2'‐Hydroxyphenyl) Benzoxazole Ancillary Ligands

Hybrid Tandem White OLED with Long Lifetime and 150 Lm W⁻¹ in Luminous Efficacy Based on TADF Blue Emitter Stabilized with Phosphorescent Red Emitter

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High-performance fluorescent/phosphorescent (F/P) hybrid white OLEDs consisting of a yellowish-green phosphorescent emitter

Abstract: F/P WOLEDs with a high luminous efficiency and a high color rending index have been achieved by employing a yellowish green emitter.

Cited by 38 publications

References 57 publications

69‐1: Invited Paper: Trap‐dependent Electrical Characteristics of Organic Semiconductor Devices

69‐1: Invited Paper: Trap‐dependent Electrical Characteristics of Organic Semiconductor Devices

Phosphorescent Cyclometalated Iridium(III) Complexes Bearing Ethynyl‐Extended 2‐(2'‐Hydroxyphenyl) Benzoxazole Ancillary Ligands

Hybrid Tandem White OLED with Long Lifetime and 150 Lm W−1 in Luminous Efficacy Based on TADF Blue Emitter Stabilized with Phosphorescent Red Emitter

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Product

Resources

About

Hybrid Tandem White OLED with Long Lifetime and 150 Lm W⁻¹ in Luminous Efficacy Based on TADF Blue Emitter Stabilized with Phosphorescent Red Emitter