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- 实验方案
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Substitutional effect of different bridging groups on optical and charge transfer properties of small bipolar molecules for OLEDs
摘要： In this work, a series of eight different bipolar molecules were designed and calculated using density functional theory (DFT) and time‐dependent functional theory (TD‐DFT) for organic light emitting diodes (OLEDs) as efficient luminescent and charge transfer materials. The eight donor‐π‐donor type small molecules (D1‐D8) were composed of triphenylamine (TPA) donor (D) unit connected to 1,8‐naphthalimides (NI) acceptor (A) unit though different π‐conjugated or R‐groups (as π‐spacer). The effect of substitutions made in π‐spacer was investigated on optical, electronic, and stability properties. This calculation analysis showed that different substitutions in π‐spacer resulted smaller Eg (range from 1.63 to 2.00 eV), broader absorption with the lowest excitation energy covering both visible and near infrared regions of solar spectrum, especially D3, D4, D5, and D6 molecules. The analyses of local densities of states, frontier molecular orbitals, and natural population analysis of orbitals revealed that studied molecules exhibited π‐π* electronic transitions of absorption in singlet excited states, but D5 and D6 also show intramolecular charge transfer (ICT) characteristics. The study of chemical indices, molecular electrostatic potential (MEP) surfaces, and charge transfer properties turned out that D4, D5, and D6 are expected to show good potential for luminescent and hole transport materials in the favor of OLEDs.
关键词： DFT,organic light emitting diodes (OLEDs),optical properties,absorption spectra,electronic structures
更新于2025-09-19 17:13:59
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5H-Benzo[d]Benzo[4,5]Imidazo[2,1-b][1,3]Thiazine as a Novel Electron-Acceptor Cored High Triplet Energy Bipolar Host Material for Efficient Solution-Processable Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes
摘要： Organic entities that can transport electrons are seldom available to develop adequate bipolar host materials applicable for solution-processable thermally activated delayed ?uorescence (TADF)-organic light-emitting diodes (OLEDs). Therefore, the introduction of new electron-af?ne entities that plausibly demonstrate high triplet energy (ET) is of urgent need. In this contribution, we introduced benzimidazo[1,2-a][3,1]benzothiazine (BBIT) as a novel electron-af?ne entity and developed two new bipolar host materials, CzBBIT and 2CzBBIT. Both host materials exhibit high ET of 3.0 eV, superior thermal robustness with the thermal decomposition temperature of up to 392?C, a glass transition temperature of up to 161?C, and high solubility in common organic solvents. Consequently, the solution-processable OLEDs fabricated using a recognized IAcTr-out as the green TADF emitter doped into CzBBIT as the host, realized a maximum external quantum ef?ciency (EQE) of 23.3%, while the 2CzBBIT:IAcTr-out blend ?lm-based device displayed an EQE of 18.7%. These outcomes corroborated that this work could shed light on the scienti?c community on the design of new electron-af?ne entities to establish the effective use of bipolar host materials toward pro?cient solution-processable TADF-OLEDs.
关键词： bipolar hosts,new electron-acceptor core,thermally activated delayed ?uorescence,organic light emitting diodes,solution process
更新于2025-09-19 17:13:59
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24.2: <i>Invited Paper:</i> High‐resolution OLED Display Fabricated by Electrohydrodynamic Printing Method
摘要： A high resolution OLED display was fabricated by using electrohydrodynamic printing method. The printed inks were poly(dibenzothiophene-S, S-dioxide-co-9,9-dioctyl-2,7-fluorene) (PPF-SO). Both of the printer operation voltage and the solvent properties dominated the ink’s printability and printing stability. Line widths of the printed polymers could be controlled. A mono-color display with resolution over 2000 PPI was realized. The electrohydrodynamic printing method for fabrication of OLED displays will be discussed in the presentation.
关键词： High resolution,Organic light-emitting diodes,Solution process,Electrohydrodynamic printing
更新于2025-09-19 17:13:59
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Influence of nonradiative Auger process in the lanthanide complexes lifetime near interfaces in organic light-emitting diode structures
摘要： The low efficiency of organic light-emitting diodes based on lanthanide complexes is generally attributed to the triplet-triplet annihilation processes in the regime of high concentration of excited states caused by their long lifetimes and optical losses near the interfaces of multilayer device structures. Despite the enormous effort to synthesize short-lived complexes and minimize the optical losses in the interfaces, it remains insufficient in understanding the exciton recombination processes that reduce the lifetime of these complexes. Herein, we investigated the influence of the exciton recombination processes on a Tb complex (Tb-C) lifetime in the regime of a highly excited state concentration as a function of the distance between the carrier layer and the interface by using a typical organic light-emitting diode structure. Our results show that a 10 nm-thick Alq3 layer decreases the exciton lifetime of the Tb-C, increasing approximately by 16 times the spontaneous emission decay rate of triplet exciton. The effects of interference and optical losses at the metallic interface contribute actively to the modulation of the emission intensity and lifetime decay. However, these effects alone do not explain the significant increase in the emission decay rate. The nonradiative Auger process at the Alq3/Tb-C interface seems to be largely accountable for the Tb-C lifetime reduction as the energy released by the terbium ion occurs by the excitation of an adjacent electron at higher energy. Furthermore, we propose a simple theoretical model to explain the observed effects. These results can provide a new approach to reduce the lanthanide complexes’ lifetime through the Auger electron process near the interface and thus improve the performance of organic light-emitting diodes.
关键词： exciton recombination,Auger process,organic light-emitting diodes,lifetime reduction,lanthanide complexes
更新于2025-09-19 17:13:59
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Modulating the luminance of organic light-emitting diodes via optical stimulation of a photochromic molecular monolayer at transparent oxide electrode
摘要： Self-assembled monolayers (SAMs) deposited on bottom electrodes are commonly used to tune charge carrier injection or blocking in optoelectronic devices. Beside the enhancement of device performance, the fabrication of multifunctional devices in which the output can be modulated by multiple external stimuli remains a challenging target. In this work, we report the functionalization of an indium tin oxide (ITO) electrode with a SAM of a diarylethene derivative designed for optically control the electronic properties. Following the demonstration of dense SAM formation and its photochromic activity, as a proof-of-principle, an organic light-emitting diode (OLED) embedding the light-responsive SAM-covered electrode was fabricated and characterized. Optically addressing the two-terminal device by irradiation with ultraviolet light doubles the electroluminescence. The original value can be restored reversibly by irradiation with visible light. This expanded functionality is based on the photoinduced modulation of the electronic structure of the diarylethene isomers, which impact the charge carriers’ confinement within the emissive layer. This approach could be successfully exploited in the field of opto-communication technology, for example to fabricate opto-electronic logic circuits.
关键词： photochromic,optoelectronic devices,diarylethene,Self-assembled monolayers,organic light-emitting diodes
更新于2025-09-19 17:13:59
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Nanosecond-time-scale delayed fluorescence molecule for deep-blue OLEDs with small efficiency rolloff
摘要： Aromatic organic deep-blue emitters that exhibit thermally activated delayed fluorescence (TADF) can harvest all excitons in electrically generated singlets and triplets as light emission. However, blue TADF emitters generally have long exciton lifetimes, leading to severe efficiency decrease, i.e., rolloff, at high current density and luminance by exciton annihilations in organic light-emitting diodes (OLEDs). Here, we report a deep-blue TADF emitter employing simple molecular design, in which an activation energy as well as spin–orbit coupling between excited states with different spin multiplicities, were simultaneously controlled. An extremely fast exciton lifetime of 750 ns was realized in a donor–acceptor-type molecular structure without heavy metal elements. An OLED utilizing this TADF emitter displayed deep-blue electroluminescence (EL) with CIE chromaticity coordinates of (0.14, 0.18) and a high maximum EL quantum efficiency of 20.7%. Further, the high maximum efficiency were retained to be 20.2% and 17.4% even at high luminance.
关键词： deep-blue OLEDs,organic light-emitting diodes (OLEDs),small efficiency rolloff,Nanosecond-time-scale delayed fluorescence,thermally activated delayed fluorescence (TADF)
更新于2025-09-19 17:13:59
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High-efficiency near-infrared fluorescent organic light-emitting diodes with small efficiency roll-off based on AIE-active phenanthro[9,10- <i>d</i> ]imidazole derivatives
摘要： The simultaneous realization of high-efficiency and low-cost in fluorescent organic light-emitting diodes (OLEDs) is still a formidable challenge in deep-red (DR)/near-infrared (NIR) region because of the intrinsic limitation of the energy-gap law and fluorescence quenching effect. Herein, three novel donor-acceptor-donor′ (D-A-D′) fluorophores, PIBz-10-PTZ, PIBz-10P-PTZ and PIBz-3-PTZ, by utilizing phenanthro[9,10-d]imidazole and phenothiazine as the donor, benzothiadiazole as the acceptor are synthesized. Owing to the unilateral steric hindrance between adjacent hydrogen atoms along the horizontal axis, PIBz-3-PTZ possesses a completely planar conformation and fully conjugated structure. PIBz-3-PTZ exhibits a strong DR emission and aggregation induced emission (AIE) property with a high photoluminescence quantum yield of 35% in neat thin film. The nondoped OLEDs achieved a maximum external quantum efficiency (EQE) of 2.02% with an emission peak at 672 nm and the brightness of up to 3403 cd m-2. In addition, the device was able to maintain an EQE of 1.69% at high luminance of 100 cd m-2, with a low efficiency roll-off of 16%, suggesting the nondoped device can keep the brightness.
关键词： Near-Infrared,High-Efficiency,AIE-active,Phenanthro[9,10-d]imidazole Derivatives,Organic Light-Emitting Diodes,Small Efficiency Roll-Off,Fluorescent
更新于2025-09-19 17:13:59
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Improved Charge Injection and Transport of Light-Emitting Diodes Based on Two-Dimensional Materials
摘要： Light-emitting diodes (LEDs) are considered to be the most promising energy-saving technology for future lighting and display. Two-dimensional (2D) materials, a class of materials comprised of monolayer or few layers of atoms (or unit cells), have attracted much attention in recent years, due to their unique physical and chemical properties. Here, we summarize the recent advances on the applications of 2D materials for improving the performance of LEDs, including organic light emitting diodes (OLEDs), quantum dot light emitting diodes (QLEDs) and perovskite light emitting diodes (PeLEDs), using organic ?lms, quantum dots and perovskite ?lms as emission layers (EMLs), respectively. Two dimensional materials, including graphene and its derivatives and transition metal dichalcogenides (TMDs), can be employed as interlayers and dopant in composite functional layers for high-e?ciency LEDs, suggesting the extensive application in LEDs. The functions of 2D materials used in LEDs include the improved work function, e?ective electron blocking, suppressed exciton quenching and reduced surface roughness. The potential application of 2D materials in PeLEDs is also presented and analyzed.
关键词： perovskite light emitting diodes,quantum dot light emitting diodes,organic light emitting diodes,two-dimensional materials
更新于2025-09-16 10:30:52
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High Efficiency Solution-Processed Organic Light-Emitting Diodes with Tetradentate Platinum(II) Emitters
摘要： The realization of high efficiency solution-processed organic light-emitting diodes (OLEDs) by using phosphorescent tetradentate Pt(II) emitters and bipolar organic hosts is demonstrated in this work. To investigate the effect of organic host on the platinum dopant, the performances of solution-processed Pt-OLEDs with various combination between four tetradentate Pt(II) emitters, including two newly developed tetra-Pt-S2 and tetra-Pt-S3, and three bipolar organic hosts m-TPAPy, o-TPAPy, and o-CzPy, have been analyzed and compared. Among the tetradentate Pt(II) complexes studied in this work, tetra-Pt-S3 exhibited the best electroluminescent performance attributable to its bulky molecular scaffold structure, high emission quantum yield, and good solubility in common organic solvents. High external quantum efficiencies (EQEs) of up to 22.4% were achieved in the solution-processed OLED with tetra-Pt-S3 emitter and m-TPAPy host at the dopant concentration of 4 wt%. At a high luminance of 1000 cd m-2, the EQE of this device decreased slightly to 21.0%.
关键词： high efficiency,platinum complexes,organic light-emitting diodes,solution-process,bipolar organic host
更新于2025-09-16 10:30:52
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Recent advances in circularly polarized electroluminescence based on organic light-emitting diodes
摘要： Since the first attempt that was made to obtain direct circularly polarized (CP) light from OLEDs by Meijer et al. in 1997, considerable efforts have been devoted to the development of circularly polarized organic light-emitting diodes (CP-OLEDs), particularly in the recent years. Circularly polarized electroluminescence (CPEL) based on OLEDs has attracted increasing interest for its efficient ability to generate CP light directly and wide potential applications in 3D displays, optical data storage, and optical spintronics. In this review, we systematically summarize the recent progress in chiral emitter based OLEDs with CPEL properties including CPEL based on chiral conjugated polymers, CPEL based on chiral metal complexes, and CPEL based on chiral simple organic molecules, especially chiral thermally activated delayed fluorescence (TADF) molecules. We believe that this review will provide a promising perspective of chiral emitter based OLEDs with CPEL properties for a broad range of scientists in different disciplinary areas and attract a growing number of researchers to this fast-growing research field.
关键词： chiral simple organic molecules,circularly polarized electroluminescence,thermally activated delayed fluorescence,chiral conjugated polymers,organic light-emitting diodes,chiral metal complexes
更新于2025-09-16 10:30:52