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Bright Deep Blue TADF OLEDs: The Role of Triphenylphosphine Oxide in NPB/TPBi:PPh <sub/>3</sub> O Exciplex Emission
摘要： Very bright (≈14 000 cd m?2) deep blue exciplex organic light emitting diodes (OLEDs) peaking at ≈435 nm, where the photopic response is ≈0.033, and with CIE color coordinates (0.1525, 0.0820), are described. The OLED properties are interestingly linked to PPh3O (triphenylphosphine oxide) and attributes of the emitting layer (EML) comprising NPB interfacing host:guest TPBi:PPh3O 5:1 weight ratio. A neat PPh3O layer that is central for device performance follows the EML (NPB/TPBi:PPh3O 5:1/PPh3O). The bright electroluminescence originates from NPB/TPBi:PPh3O exciplexes involving triplets via thermally activated delayed fluorescence, as evident from the strong quenching of the photoluminescence (PL) by oxygen and interestingly, the monomolecular emission process. The transient PL decay times of a NPB/TPBi:PPh3O 5:1/PPh3O film are 43 ns in air versus 136, 610, and weak ≈2000 ns in N2. For comparison, the respective PL decay times of films of NPB:TPBi are 16 ns in air versus 131 and 600 ns in N2, and of NPB:PPh3O they are 29 ns in air versus 56, 483, and weak ≈2000 ns in N2. It is suspected that slow emitting states are associated with a PPh3O aggregate interacting with NPB.
关键词： all-organic OLEDs,exciplex TADF OLEDs,bright deep blue OLEDs
更新于2025-09-12 10:27:22
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The effect of molecular structure on the properties of quinoxaline-based molecules for OLED applications
摘要： Different donor-acceptor-donor (D-A-D) and donor-π-bridge-acceptor-π-bridge-donor (D-π-A-π-D) systems based on quinoxaline acceptor are compared. A significant difference in electrochemical and photophysical properties was found depending on molecular structure. A luminescence shift from 539 nm up to 671 nm was observed upon extension of conjugation length. The studied compounds were tested in fluorescent organic light emitting diodes (OLEDs) demonstrating an external quantum efficiency up to 4.5 % for the deep red non-doped device and 7% for the doped into the exciplex host device. A quantum-chemical interpretation of the electroluminescence spectra for the fabricated OLEDs was carried out including modelling of excimers and exciplexes.
关键词： OLEDs,conjugation length,Quinoxaline,donor-acceptor,organic emitter,exciplex
更新于2025-09-12 10:27:22
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Molecular Engineering of Thermally Activated Delayed Fluorescence Emitters with Aggregation-Induced Emission via Introducing Intramolecular Hydrogen-Bonding Interactions for Efficient Solution-Processed Nondoped OLEDs
摘要： Purely organic luminescent materials concurrently exhibiting thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) features are in great demand due to their high efficiency in aggregation-state toward efficient non-doped OLEDs. Herein, a class of thermally activated delayed fluorescence (TADF) emitters adopting phenyl(pyridyl)methanone as electron-accepting segment and di(tert-butyl)carbazole and 9,9-dimethyl-9,10-dihydroacridine (or phenoxazine) as electron-donating groups are designed and synthesized. The existence of intramolecular hydrogen bonding is conducive to minish the energy difference between singlet and triplet (ΔEst), suppress non-radiative decay and increase the luminescence efficiency. By using 3CPyM-DMAC as emitter, the non-doped device via solution process realize high current efficiency (CE) and external quantum efficiency (EQE) of 35.4 cd A-1 and 11.4 %, respectively, which is superior to that of CBM-DMAC with CE and EQE of 14.3 cd A-1 and 6.7 %. This work demonstrates a promising tactics to the establishment of TADF emitters with AIE features via introducing intramolecular hydrogen-bonding.
关键词： organic light-emitting diodes (OLEDs),nondoped,thermally activated delayed fluorescence (TADF),solution processed,aggregation-induced emission (AIE)
更新于2025-09-12 10:27:22
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The one-pot synthesis of homoleptic phenylphthalazine iridium(III) complexes and their application in high efficiency OLEDs
摘要： A series of homoleptic cyclometalated iridium (III) complexes bearing a 1-phenylphthalazine framework have been synthesized with a facile one-pot method and characterized by X-ray single crystal diffraction. All complexes exhibited orange or red emission peaks at 583–623 nm with short lifetimes of 1.3–2.6 μs and high photoluminescence quantum yields of 41%–82%. These complexes exhibit good thermal stability with high Td of 275–394 °C. The electronic states and orbital distributions of these iridium (III) complexes were studied by density functional theory. These complexes were used as emissive materials in Organic light-emitting diodes (OLEDs). The device based on 2 gave a peak current efficiency and external quantum efficiency (EQE) of 35.1 cd A?1 and 21.2%, respectively. The color coordinates of device based on 3 fully meet that of standard red of the National Television Standards Committee (NTSC). These results suggest that homoleptic phenylphthalazine iridium (III) complexes have potential application as efficient emitters in OLEDs.
关键词： One-pot reaction,OLEDs,Phenylphthalazine,Homoleptic cyclometalated iridium(III) complex
更新于2025-09-12 10:27:22
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Lowering the power of OLEDs
摘要： Lower power OLED displays could emerge from the latest work from an international collaboration between researchers at RIKEN, the University of California San Diego, the University of Tokyo, and the Institute for Molecular Science. Organic light emitting diodes (OLEDs) have been with us for many years now. They offer many advantages over other types of display based on inorganic LEDs and liquid crystal displays. They can be ?exible, thin, and preclude the need for a power-draining backlight. Writing in the journal Nature, the team explains how they have found a new way to manipulate the “excitons”-the electron-hole pairs that are key for charge transport within an OLED. The team points out that a current passing through an OLED device creates exciton pairs and when these drop down to a lower energy level, they emit visible light in a quantum process. OLED excitons arise in one of two patterns - the spins are either in the same direction or opposing. The former, so-called triplet excitons, are three times more common than the latter, the singlet excitons. Singlet excitons are formed only at higher energy and they can ultimately convert into triplets, but it would cut energy costs in a device if singlets were not formed at all. The team has now demonstrated that lowering the voltage so that only triplets are formed is possible where it was always assumed this would not work. They used electroluminescence measurements with a scanning tunneling microscope (STM) and an optical detection system to observe the formation of excitons. A model system with a single, isolated molecule of the organic semiconductor 3, 4, 9, 10-perylenetetracarboxylic-dianhydride (PTCDA) on metal-supported ultrathin insulating ?lm was key to their understanding. By imparting a negative charge to this supported molecule, they could use the STM tip to induce luminescence in the molecule, and monitored record the emission spectrum of the resulting excitons. Critically, at low voltage, only triplets form. Theoretical calculations support the suggested mechanism.
关键词： OLEDs,scanning tunneling microscope,PTCDA,singlet excitons,electroluminescence,triplet excitons,excitons
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 2nd International Conference on Electronics Technology (ICET) - Chengdu, China (2019.5.10-2019.5.13)] 2019 IEEE 2nd International Conference on Electronics Technology (ICET) - High Efficiency Fully Inkjet Printed Multilayer OLEDs Using A Printable Organic Electronic Transport Layer
摘要： High efficiency fully inkjet printed multilayer OLEDs have been successfully developed using a printable organic electronic transport layer (ETL). Through a proper selection of solvents, we prepared a jettable and stable ETL ink with commercially soluble electronic transport material. The fully inkjet printed multilayer green phosphorescent OLEDs showed a high luminous efficiency of 55.5 cd A-1 at a brightness of 1000 cd m-2 with an external quantum efficiency (EQE) of 14.8%. The results demonstrated that the solution deposition of inkjet printed ETL caused little damage to the underlying emission layer (EML).
关键词： solution deposition,printable electronic transport layer,multilayer OLEDs,fully inkjet printed
更新于2025-09-12 10:27:22
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Simulation of Multilayer Energy Efficient OLEDs for Flexible Electronics Applications
摘要： Organic light emitting (OLEDs) work on electro luminescence principles and these OLEDs are commercially available and can be used in display because of the low power consumption. Proposed research deals with the design of high-efficiency OLEDs, including electrical and optical design of OLEDs. The Luminescent efficiency of bilayer and Triple layer OLED experiment and analysis was done using the Silvaco TCAD tool in this research work. The simulation of electronics and optical features such luminescence power versus anode voltage, anode voltage versus anode current characteristics and exciton state of both bilayer and Triple layer OLEDs were discussed. The physical design, processes as well as principles of OLED has been discussed and operational distribution of Langevin recombination inside proposed structures were acquired and discussed.
关键词： Efficiency Improvement,Organic Light emitting diode (OLEDs),Multilayer,TCAD
更新于2025-09-12 10:27:22
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Exciplex hosts for blue phosphorescent organic light-emitting diodes
摘要： The host material of organic light-emitting diodes (OLEDs) has been advanced from a single host to a mixed host for high efficiency and long lifetime. Several types of mixed host have been reported in the literature, but the exciplex host has been popular as the mixed host of OLEDs. The exciplex host has been developed mostly for red and green phosphorescent OLEDs, and has upgraded device performances, but it is difficult to develop the exciplex host for blue phosphorescent OLEDs. Recently, several works demonstrated the potential of the exciplex host for blue phosphorescent OLEDs. In this paper, the exciplex host for blue OLEDs is reviewed, and its prospects are presented.
关键词： OLEDs,Exciplex host,quantum efficiency,blue phosphorescent device
更新于2025-09-12 10:27:22
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Inside or outside: Evaluation of the efficiency enhancement of OLEDs with applied external scattering layers
摘要： Improving the efficiency of organic light-emitting diodes (OLEDs) by enhancing light outcoupling is common practise and remains relevant as not all optical losses can be avoided. Especially, externally attached scattering layers combine several advantages. They can significantly increase the performance and neither compromise the electric operation nor add high costs during fabrication. Efficiency evaluations of external scattering layers are often done with lab scale OLEDs. In this work we therefore study different characterization techniques of red, green and blue lab scale OLEDs with attached light scattering foils comprising TiO2 particles. Although we observe an increased external quantum efficiency (EQE) with scattering foils, our analysis indicates that areas outside the active area have a significant contribution. This demonstrates that caution is required when efficiency conclusions are transferred to large area applications, for which effects that scale with the edges become less significant. We propose to investigate brightness profiles additionally to a standard EQE characterizations as latter only work if the lateral scattering length is much smaller than the width of the active area of the OLED. Our results are important to achieve more reliable predictions as well as a higher degree of comparability between different research groups in future.
关键词： external scattering layers,efficiency enhancement,OLEDs,EQE,light outcoupling
更新于2025-09-12 10:27:22
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Cruciform Molecules Bearing Bis(phenylsulfonyl)benzene Moieties for High‐Efficiency Solution Processable OLEDs: When Thermally Activated Delayed Fluorescence Meets Mechanochromic Luminescence
摘要： Four crucifix-shaped molecules, named TPA-BPSB, DMAc-BPSB, MTPA-BPSB and MDMAc-BPSB, bearing the same acceptor fragment of bis(phenylsulfonyl)benzene (BPSB) and different donor segments (TPA and MTPA are the diphenylamine derivatives while DMAc and MDMAc are the 9,9-dimethylacridine derivatives) are synthesized and characterized by NMR, mass spectra, and single crystal X-ray crystallography. The molecular structure–property relationship of these crucifix-shaped molecules is systematically explored. All compounds display thermally activated delayed fluorescence (TADF) in the region of 500–550 nm. In addition, charming mechanochromic luminescence properties are observed for all these TADF molecules under external stimuli, such as grinding and exposure to CH2Cl2 vapor. Four TADF molecules are used as the emitters in organic light-emitting diodes (OLEDs) fabricated via solution process. MTPA-BPSB-based device presents a best performance with a highest external quantum efficiency of ≈21%, which is among the highest efficiencies for reported BPSB-based solution-processable OLEDs so far. This research has an important significance in designing high-efficiency multifunctional TADF molecules.
关键词： bis(phenylsulfonyl)benzene,thermally activated delayed fluorescence,mechanochromic luminescence,crucifix-shaped molecules,solution processable OLEDs
更新于2025-09-12 10:27:22