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Elucidating the effects of guest-host energy level alignment on charge transport in phosphorescent OLEDs
摘要： The correct choice of guest and host molecules in the light-emitting layer is essential for developing high performance phosphorescent organic light emitting devices. However, the effects of the energy level alignment between the guest and the host are yet to be fully elucidated. In this Letter, we use kinetic Monte Carlo simulations to investigate guest-host systems in which the energy gap of the guest and host is fixed, and only the relative energies of the ionization potential/electron affinity are changed to elucidate their effect on charge transport. It was determined that the mobility balance in the blend was sensitive to the energy level alignment, allowing balanced active layer mobility to be achieved despite the hole and electron mobilities being different by around one order of magnitude. It was also found that the mobility of the faster carrier was more sensitive to the energy level alignment than that of the slower carrier due to reduced slower carrier thermalization under deep charge trapping on the guest.
关键词： guest-host energy level alignment,phosphorescent OLEDs,kinetic Monte Carlo simulations,charge transport
更新于2025-09-12 10:27:22
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Novel phosphorescent triptycene-based Ir( <scp>iii</scp> ) complexes for organic light-emitting diodes
摘要： A series of charge-neutral cyclometalated iridium(III) complexes (1–3 and 5–7) containing triptycene-substituted ligands (tbt and tpbi) and two parent complexes (4 and 8) were synthesized and characterized. The crystal structures indicated that π–π stacking interactions existed in ligand tbtH, but not in complex 6. However, a large intramolecular repulsion was found in complex 6. These triptycene-based complexes exhibited good thermal stability, which was higher compared with that of the parent complexes. These complexes showed green to yellow emission with peaks that ranged from 503 to 563 nm. The introduction of the rigid non-conjugate triptycene skeleton caused a slight emission red shift (<25 nm), but a significant increase in the PLQYs (>47%) was observed. The electroluminescent devices employing 2 and 6 as phosphors displayed impressive performance improvements and low efficiency roll-off because of the higher PLQYs and HOMO levels of these triptycene-based complexes. The maximum current and external quantum efficiencies of the devices based on complexes 2 and 6 were 41.7 cd A?1, 11.9% and 41.2 cd A?1, 12.6%, respectively, which were about 31% higher than that of the devices based on the parent complexes 4 and 8. This work provides a novel approach to develop highly efficient phosphors with a triptycene skeleton.
关键词： Ir(III) complexes,triptycene,thermal stability,phosphorescent,OLEDs,PLQYs
更新于2025-09-12 10:27:22
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OLEDs with Candle-Like Emission
摘要： Candle-like organic light-emitting diodes (OLEDs) emit much less blue light than other non-incandescent light sources. This type of OLED is characterized by low correlated color temperature (CCT), chromaticity tunability, and low melatonin (MLT) suppression. The light evokes a sense of warmth and creates a pleasant and calming ambience with its high-quality diffuse orange-red emission.
关键词： OLEDs,Color Temperature,Candle-Like Emission,Blue Light,Melatonin Suppression
更新于2025-09-12 10:27:22
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Towards Solution-Processed Top-Emitting OLEDs Using a Phosphorescent Iridium Complex
摘要： Phosphorescent inverted top-emitting OLEDs using green iridium complexes have been fabricated by spin coating and their performances compared to bottom-emitting OLEDs based on the same materials. Even if the current efficiency is lower, respectively 7.0 ± 1.1 cd.A-1 and 12.9 ± 1.9 cd.A-1, this paper demonstrates the feasibility to fabricate phosphorescent top-emitting OLEDs by using a solution process with a simple OLED structure and replacing indium tin oxide electrode by a low-cost reflective aluminum electrode. Optical characterization of the top-emitting OLEDs shows a low emission shift compared to the spectrum of bottom-emitting OLED. A low angle dependency of the electroluminescence peak wavelength is observed , showing it is possible to control and minimize the microcavity effects for solution-processed top-emitting OLEDs.
关键词： phosphorescent emitters,solution process,top-emitting organic light-emitting diodes (OLEDs)
更新于2025-09-12 10:27:22
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Human-eyes-friendly white electroluminescence from solution-processable hybrid OLEDs exploiting new iridium (III) complex containing benzoimidazophenanthridine ligand
摘要： This paper primarily deals with the development of highly efficient phosphorescent iridium (III) complex based on benzoimidazophenanthridine as main ligand. The potential of this complex, as phosphorescent emitter for optoelectronic applications, was screened by different methods, including luminescence spectrometry, cyclic voltammetry, thermogravimetric analysis, differential scanning calorimetry as well as photoelectron emission spectrometry. The possible application of the developed complex in single-colour vacuum-deposited organic light emitting diodes (OLEDs) exhibiting warm orange electrophosphorescence was demonstrated. The device was characterized with CIE1931 colour coordinates of (0.539, 0.459), colour temperature of 2088 K and maximum external quantum efficiency of 17.5 %. Good performance in OLEDs can be partly explained by efficient orange phosphorescence with quantum yield of 60 % at room temperature. This paper also deals with the development of white hybrid solution-processable organic light-emitting devices, exploiting ultralow concentration of newly synthesized iridium (III) complex as phosphorescent dopant in combination with blue fluorescencent emitter(host), and green emitter exhibiting thermally activated delayed fluorescence emitter. It was designed and fabricated by spin coating white hybrid devices, and was characterized by high quality (human-eyes-friendly) electroluminescence achieving CIE1931 coordinates of (0.335, 0.392), colour temperature of 2910K and colour rendering index of 72 as well as high maximum external quantum efficiency of 8.7 %.
关键词： external quantum efficiency,electrophosphorescence,phosphorescent iridium (III) complex,benzoimidazophenanthridine,white hybrid OLEDs,solution-processable,organic light emitting diodes (OLEDs)
更新于2025-09-11 14:15:04
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Structurally simple OLEDs based on a new fluorinated poly(oxindolylidenearylene)
摘要： Organic light emitting diodes (OLEDs) based on a new polymer; are reported. This new polymer; Poly[(Benzo[c][1,2,5]thiadiazole-4,7-diylbis(9,9-dimethyl-9H-fluorene-7,2-diyl))-3,3-diyl(1-(3-(trifluoromethyl)phenyl)-2-oxindole)] (PF-2F), was used as emissive layer (EML), with a relatively simple architecture ITO/PEDOT:PSS/polymer/(LiF or PFN)/A, which is a modified version of our previously reported; PF-1: Poly[(Benzo[c][1,2,5]thiadiazole-4,7-diylbis(9,9-dimethyl-9H-fluorene-7,2-diyl(1-phenyl-2-oxindole)], applied in OLEDs and lasing devices. The main difference between these two polymers, is the trifluoromethyl (CF3) group addition to the PF-2F. CF3 leads to improved OLEDs electroluminescence and better EQEmax; due to enhanced mechanical properties, higher solubility and higher fluorescence quantum yield (FLQY). PF-1 and PF-2F polymers have an excellent FLQY: ~1. Polymer films (by spin coating) show low roughness value (~ 1-2 nm), just like polymers in OLEDs. OLEDs based on the modified polymer (with yellow-green electroluminescence (EL) emission) showed luminances of up to 1937 cd/m2, current efficiencies of up to 35 cd/A and maximum external quantum efficiency (EQEmax) of up to 2.6 %. Additionally, promising preliminary results on flexible OLEDs using PF-2F and PEDOT: PSS conductive (PH1000) (as anode) are reported.
关键词： Donor-Acceptor,Spin coating,Fluorinated polymer PF-2F,simple OLEDs
更新于2025-09-11 14:15:04
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The photophysical properties and electronic structures of bis[1]benzothieno[6,7-d:6',7'-d']benzo[1,2-b:4,5-b']dithiophene (BBTBDT) derivatives as hole-transporting for organic light-emitting diodes (OLEDs)
摘要： By using the quantum methods DFT and TD-DFT in this paper, the optoelectronic properties and electronic structures of eight compounds Ci (i=1-8) based on bis[1]benzothieno[6,7-d:6',7'-d']benzo[1,2-b:4,5-b']dithiophene (BBTBDT) with D-π-D structure for Ci (i=1-5); and D-π-A for Ci (i=6-8) have been calculated and discussed theoretically in the aim to consider them as hole-transporting materials (HTM) in OLEDs. The calculated electronic levels by B3LYP of studied compounds show that the proper energy of Ci (i=6-8) is so matching for efficiency injecting into hole-injection layer (HIL). The compounds having D-π-A structure seem more efficient than those having D-π-D structure. The optoelectronic properties for studied compounds obtained by TD-CAM-B3LYP elucidate that C6, C7 and C8 compounds behave as electron donating molecules and induce charge transfer character in the UV-visible absorptions and emission electronic spectra. Furthermore, the calculated reorganization energies, ionization potential (IP) and electron affinity (EA) also provide that the extended C6, C7 and C8 compounds have the highest charge-transporting ability among all compounds. It is found that the D-π-A more influence on the electronic and optoelectronic properties than the D-π-D structure. The assumed compound C7 is found to be a good candidate for blue-emitting material. Understanding these properties is important to design HTMs with exceptional properties, such as stability and high efficiency.
关键词： B3LYP,DFT,bis[1]benzothieno[6,7-d:6',7'-d']benzo[1,2-b:4,5-b']dithiophene (BBTBDT),OLEDs
更新于2025-09-11 14:15:04
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[IEEE 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Berlin, Germany (2019.6.23-2019.6.27)] 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - High-Color-Purity Microfluidic Quantum Dots Light-Emitting Diodes Using the Electroluminescence of the Liquid Organic Semiconductor Backlight
摘要： We proposed microfluidic quantum dots light-emitting diodes using a liquid organic semiconductor (LOS) and quantum dots (QDs) solutions. LOS and QDs solutions were used as a backlight and a luminophore, respectively. Channels for the QDs solutions were stacked on the LOS backlight. With applying voltage, red photoluminescence (PL) emissions of the QDs solution excited by the LOS backlight, was observed. The full width at half maximum of the red-PL emission was 29.8 nm, which is narrower than that of the LOS backlight by 40%. The proposed device is expected to provide highly-bright flexible displays with high-color-purity.
关键词： liquid organic semiconductor (LOS),Liquid organic light-emitting diodes (OLEDs),high-color-purity,functional organic liquid,quantum dots light-emitting diodes (QLEDs)
更新于2025-09-11 14:15:04
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Unveiling the Root Cause of the Efficiency-Lifetime Trade-Off in Blue Fluorescent Organic Light-Emitting Diodes
摘要： The origin of efficiency-lifetime trade-off in triplet–triplet fusion (TTF) type blue fluorescent organic light-emitting diodes (OLEDs) was investigated and the device structure to resolve the issue was developed. The efficiency and lifetime were simultaneously improved in the blue OLEDs by developing a multilayer hole transport stack which can adjust carrier densities and recombination zone in the emitting layer (EML). It was found that electron leakage from EML and high spatial density of excitons in the vicinity of the electron blocking layer for high TTF rates by narrow recombination zone are the detrimental factors for efficiency-lifetime trade-off. A multilayer hole transport stack employing a deep highest occupied molecular orbital hole transport layer and an electron blocking layer combined with an appropriate hole blocking layer simultaneously improved the power efficiency by 16% at 500 cd/m2 and lifetime by almost 100% (from 73 h up to 145 h). In addition, the low efficiency in the low luminance region was also completely controlled, resulting in negligible efficiency variation in the entire luminance range.
关键词： Efficiency-lifetime trade off,Blue fluorescent OLEDs,Triplet–triplet fusion
更新于2025-09-11 14:15:04
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Aggregation-Induced Delayed Fluorescence Luminogens with Accelerated Reverse Intersystem Crossing for High-Performance OLEDs
摘要： A fast reverse intersystem crossing (RISC) is of high importance for delayed fluorescence emitters in terms of increasing exciton utilization and suppressing efficiency roll-off. Herein, new robust luminogens comprised of carbonyl, phenoxazine and chlorine-substituted carbazole derivatives are synthesized and characterized. They own distinct aggregation-induced delayed fluorescence (AIDF) feature, and exhibit high photoluminescence efficiencies and short delayed fluorescence lifetimes in neat films. The RISC is conspicuously accelerated owing to their tiny singlet-triplet energy splitting and greatly enhanced spin-orbit coupling by heavy atom effect in neat films. They can function efficiently as light-emitting layers in nondoped OLEDs, providing excellent maximum electroluminescence (EL) efficiencies of 20.4–21.7%, and can also perform outstandingly in doped OLEDs in a wide doping concentration range (5–90 wt%), affording impressive EL efficiencies of up to 100.1 cd A–1, 104.8 lm W–1 and 29.1%, with small efficiency roll-off. These findings demonstrate the AIDF luminogens with fast RISC are promising candidates to fulfill various demands of production and application of OLEDs.
关键词： OLEDs,Reverse Intersystem Crossing,Luminogens,Aggregation-Induced Delayed Fluorescence,High-Performance
更新于2025-09-11 14:15:04