- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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High-efficiency blue phosphorescent organic light-emitting devices with low efficiency roll-off at ultrahigh luminance by reduced the triplet-polaron quenching
摘要： High performance phosphorescent organic light-emitting devices (PhOLEDs) at high luminance are still a remaining problem needing to be solved, especially blue PhOLEDs. Here, 5-(5-9H-carbazol-9-yl) pyridin-2-yl)-8-(9H-carbazol-9-yl) -5H-pyrido [3, 2-b] indole (p2PCB2CZ) with excellent characteristics as host is designed to realize a novel host-guest system without hole trapping effect in blue PhOLEDs. The device in which p2PCB2CZ and Bis (3, 5-difluoro-2-(2-pyridyl) phenyl-(2-carboxypyridyl)iridium(III) (FIrpic) is used as host and guest, respectively, is proposed to improve the performances of blue PhOLEDs at high luminance, especially ultrahigh luminance (>30000 cd/m2). The maximum external quantum efficiency (EQE) of this type blue PhOLEDs is 19.2%, while the maximum EQE of reference blue PhOLEDs is 18.7 %. Nevertheless, the p2PCB2CZ-based devices exhibit significant advantage at high luminance, because its EQE still attains to 10.8% even when the luminance increases to 30000 cd/m2, which is 1.67 times that of the reference device. From measurements based on steady-state and time-resolved spectroscopy, the reduction of triplet-polaron quenching in p2PCB2CZ-based devices is proved to the main reason for improving the performances of blue PhOLEDs at high luminance.
关键词： Ultrahigh luminance,Efficiency roll-off,Blue PhOLED,Hole trapping,Triplet-polaron quenching.
更新于2025-09-23 15:22:29
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High efficiency???low efficiency roll-off and long lifetime fluorescent white organic light-emitting diodes based on strategic management of triplet excitons via triplet-triplet annihilation up-conversion and phosphor sensitization
摘要： The simultaneous realization of high efficiency, low efficiency roll-off, long lifetime and stable electroluminescence (EL) spectra in fluorescent white organic light-emitting diodes (WOLEDs) is still a huge challenge. Here, we used a triplet-triplet annihilation up-conversion (TTA-UC) material as blue emission layer and phosphor sensitized fluorescent emitter as red emission layer and introduced a bipolar interlayer between them to fabricate high efficiency, low efficiency roll-off and long lifetime fluorescent WOLEDs. It is clearly seen that the bipolar interlayer not only efficiently distributed the singlet and triplet excitons, but also significantly stabilized the EL spectra. Thus, the resulting two-color fluorescent WOLEDs exhibited the maximum current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) of 26.9 cd A-1, 22.3 lm W-1 and 12.8%, and remained 25.9 cd A-1, 16.9 lm W-1 and 12.1% at the luminance of 1000 cd m-2 and 23.1 cd A-1, 10.6 lm W-1 and 10.7% at the luminance of 10000 cd m-2, respectively, and the operational lifetime LT50 (50% decay, initial luminance of 1000 cd m-2) was also up to 984 h. It can be seen that these devices also showed stable EL spectra with Commission Internationale de I’Eclairage (CIE) of (0.51, 0.41) from 1000 cd m-2 to 5000 cd m-2 luminance. Furthermore, the fabricated three-color fluorescent WOLEDs by further introducing a green fluorescent emitter, also showed high efficiencies of 15.5 cd A-1, 13.0 lm W-1 and 8.1% and stable EL spectra with CIE of (0.43, 0.36) form 1000 cd m-2 to 5000 cd m-2 luminance. More importantly, their CE and EQE exhibited an increasing tendency with the luminance, a fully negligible efficiency roll-off. This design strategy provides a potential route towards high performance fluorescent WOLEDs.
关键词： fluorescent WOLEDs,bipolar interlayer,high efficiency,triplet-triplet annihilation up-conversion,phosphor sensitization,long lifetime,low efficiency roll-off
更新于2025-09-23 15:21:01
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Novel strategy to improve the efficiency roll-off at high luminance and operational lifetime of hybrid white OLEDs via employing an assistant layer with triplet-triplet annihilation up-conversion characteristics
摘要： The efficiency roll-off at high luminance and operational lifetime remain a major challenge before the wide applications of white organic light-emitting diodes (WOLEDs) technology. Here we present a novel strategy to improve the efficiency roll-off at high luminance and operational lifetime by employing an assistant layer with triplet-triplet annihilation (TTA) up-conversion characteristics in emitters. It can be seen that at high luminance, the partial triplet energies in emitters will transfer to the TTA assistant layer and finally lead to the TTA emission, which reduces the exciton quenching at high luminance. Therefore, not only the efficiency roll-off, but also the operational lifetime are greatly improved. The resulting hybrid WOLEDs exhibited the maximum forward-viewing external quantum efficiency and power efficiency of 23.6% and 68.8 lm W?1, and they only dropped to 18.3% and 38.1 lm W?1 at 1000 cd m?2 and 17.1% and 25.9 lm W?1 at 5000 cd m?2, which are significantly higher than 10.5% and 17.9 lm W?1 at 5000 cd m?2 of WOLEDs without TTA assistant layer. Furthermore, the operational half-lifetime of the resulting hybrid WOLEDs also reached 600 hours at the luminance of 1000 cd m?2, which is nearly two-fold longer than that of the reference WOLEDs.
关键词： exciton diffusion,triplet-triplet annihilation up-conversion,Efficiency roll-off,white organic light-emitting diodes,lifetime
更新于2025-09-23 15:21:01
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Aggregation-induced Emission Polymers for High Performance PLEDs with Low Efficiency Roll-off
摘要： As the congener of organic light-emitting diodes, polymeric light-emitting diodes (PLEDs) possess a number of distinct merits such as low-cost wet fabrication process, which enable them applicable in large-area flexible display and lighting fields. However, most emissive polymers used in PLEDs suffer from the aggregation-caused quenching (ACQ) effect, which makes the device show large efficiency roll-off. In this work, two polymers of pTPE-TPA-Cz and pTPE-TPA-Flu featuring aggregation-induced emission (AIE) characteristics were facilely synthesized through Suzuki-Miyaura polycoupling reaction by incorporating the AIE unit of TPE-TPA in their main chains. The resultant polymers possess good film-forming ability, excellent thermal stability and high photoluminescence quantum yields (PLQY) in their film states, facilitating the fabrication of PLEDs through solution process. Indeed, the PLEDs using pTPE-TPA-Cz and pTPE-TPA-Flu as emitting layers (EMLs) could achieve a maximum external quantum efficiency (EQE) of 3.26% (doped EML) and current efficiency of 3.69 cd A-1 (non-doped EML). Notably, all the devices exhibit a quite low efficiency roll-off. This work indicates that AIE polymers are ideal candidates for the construction high performance PLEDs with low efficiency roll-off.
关键词： Aggregation-induced emission,Photoluminescence quantum yields,Solution process,Efficiency roll-off,Polymeric light-emitting diodes
更新于2025-09-23 15:21:01
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Bright CsPbI <sub/>3</sub> Perovskite Quantum Dot Light-Emitting Diodes with Top-Emitting Structure and a Low Efficiency Roll-Off Realized by Applying Zirconium Acetylacetonate Surface Modification
摘要： Zirconium acetylacetonate used as a co-precursor in the synthesis of CsPbI3 quantum dots (QDs) increased their photoluminescence quantum efficiency to values over 90%. The top-emitting device structure on a Si substrate with high thermal conductivity (to better dissipate Joule heat generated at high current density) was designed to improve the light extraction efficiency making use of a strong microcavity resonance between the bottom and top electrodes. As a result of these improvements, light-emitting diodes (LEDs) utilizing Zr-modified CsPbI3 QDs with an electroluminescence at 686 nm showed external quantum efficiency (EQE) of 13.7% at a current density of 108 mA cm?2, which was combined with low efficiency roll-off (maintaining an EQE of 12.5% at a high current density of 500 mA cm?2) and a high luminance of 14 725 cd m?2, and the stability of the devices being repeatedly lit (cycled on and off at high drive current density) has been greatly enhanced.
关键词： CsPbI3 perovskite quantum dots,top-emitting light-emitting diodes,surface modification,zirconium acetylacetonate,efficiency roll-off
更新于2025-09-23 15:21:01
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Boosting the Efficiency and Curtailing the Efficiency Roll-off in Green Perovskite Light-Emitting Diodes via Incorporating Ytterbium as Cathode Interface Layer
摘要： Perovskite light-emitting diodes (PeLEDs) exhibit high external quantum efficiencies (EQEs), emerging as a next-generation technology for lighting and display applications. Nevertheless, they suffer from severe efficiency roll-off at high luminance, particularly in case of blue and green emissions, which is one of the major bottlenecks in their industrial applications. Here, we attack this problem using a rare-earth metal, Yb, as cathode interface layer (CIL) for green PeLEDs. By adopting a new device configuration of ITO/TFB/FA-based Quasi-2D Perovskite/TPBi/Yb/Ag, we achieved a peak current efficiency (CE) of 22.3 cd/A with a corresponding EQE of 5.28% and a high maximum luminance of 19,160 cd/m2. Importantly, the maximum CE of 22 cd/A at 2,000 cd/m2 slightly decreased to 16.8 cd/A at 5,000 cd/m2 and maintained a still decent value of 12 cd/A at a very high luminance of 10,000 cd/m2, exhibiting a remarkably low efficiency roll-off. Our Yb-incorporated devices significantly outperformed the PeLEDs containing conventional CILs, including Mg and Liq, in terms of peak efficiency, efficiency roll-off and operational lifetime. We attribute this encouraging performance to barrier-free, efficient electron injection enabled by the low work function of Yb (2.6 eV) which led to a high electron current, nearly approaching the hole current in hole-dominant PeLEDs, as confirmed by the single-carrier device measurements. In addition, we also present Yb-incorporated PeLEDs containing Cs-based Quasi-2D perovskite as the emissive layer which displayed an impressive CE of 51.3 cd/A with a corresponding EQE of 16.4% and a maximum luminance of 14,240 cd/m2, and still demonstrated a reduced efficiency roll-off comparing to that of the Liq-based equivalent. These results unveil the inspiring prospects of Yb as an efficient CIL for PeLEDs towards high efficiency with reduced efficiency roll-off.
关键词： electron injection,ytterbium,quasi-2D,perovskite light-emitting diodes,stability,cathode interface layer,efficiency roll-off
更新于2025-09-23 15:21:01
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Suppressing Efficiency Roll-Off at High Current Densities for Ultra-Bright Green Perovskite Light-Emitting Diodes
摘要： Perovskite light-emitting diodes (PeLEDs) have undergone rapid development in the last several years with external quantum efficiencies (EQE) reaching over 21%. However, most PeLEDs still suffer from severe efficiency roll-off (droop) at high injection current densities, thus limiting their achievable brightness and presenting a challenge to their use in laser diode applications. In this work, we show that the roll-off characteristics of PeLEDs are affected by a combination of charge injection imbalance, nonradiative Auger recombination, and Joule heating. To realize ultrabright and efficient PeLEDs, several strategies have been applied. First, we designed an energy ladder to balance the electron and hole transport. Second, we optimized perovskite materials to possess reduced Auger recombination rates and improved carrier mobility. Third, we replaced glass substrates with sapphire substrates to better dissipate joule heat. Finally, by applying a current-focusing architecture, we achieved PeLEDs with a record luminance of 7.6 Mcd/m2. The devices can be operated at very high current densities (J) up to ~ 1 kA/cm2. Our work suggests a broad application prospect of perovskite materials for high-brightness LEDs and ultimately a potential for solution-processed electrically pumped laser diodes.
关键词： Joule heat,efficiency roll-off,Auger recombination,charge injection balance,high injection current density,ultrahigh brightness,perovskite light emitting diodes
更新于2025-09-23 15:19:57
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Investigation on OLEDs efficiency roll-off with interfacial charge storage and their time-resolved emission spectra
摘要： Organic light-emitting diodes (OLEDs) are the next generation technique of display and lighting, confronted with the bottle-neck problem of OLEDs efficiency roll-off. The nature of luminescence and efficiency roll-off of OLEDs are processes of electrons and energy, during which charge injection and storage play important roles. In order to study the mechanism of OLEDs efficiency roll-off with interfacial charge storage, organic light-emitting devices with Ir(ppy)3 doped CBP as the light-emitting layer were prepared, and PMMA layers of 5 nm, 6 nm, 8 nm and 9 nm were inserted as charge storage layers to control hole injection and hole accumulation. The OLEDs efficiency roll-off is obvious with the increase of the current density. The storage of the interfacial charges is analyzed by transient electroluminescence measurement. Luminescence spikes occur at both forward and reverse turn-off voltages, which is caused by electron diffusion and trap carriers release, respectively. The time-resolved emission spectra prove the relationship of interfacial charges and exciton quenching. The OLEDs efficiency roll-off is positively correlated with the interfacial charge storage especially at low current density. This is due to the effect of the accumulation of the interfacial charge especially under unbalanced charge injection of OLEDs, which is of importance to improve the OLEDs performance and to decrease the OLEDs efficiency roll-off in industry.
关键词： OLEDs efficiency roll-off,Transient electroluminescence measurement,Interfacial accumulated charges
更新于2025-09-23 15:19:57
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Rotation-restricted thermally activated delayed fluorescence compounds for efficient solution-processed OLEDs with EQEs of up to 24.3% and small roll-off
摘要： Two triphenylamine or 4,4’-di(tert-butyl)triphenylamine groups are introduced at 1,8-positions of 3,6-di(tert-butyl)-9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)carbazole to yield two emitters containing a cofacial donor-acceptor-donor chromophore, which exhibit strong TADF characteristic dominated by through-space charge-transfer. The solution-processed OLEDs achieve the maximum external quantum efficiencies of up to 17.4% and 24.3% with small efficiency roll-off rate.
关键词： Thermally Activated Delayed Fluorescence,solution-processed,efficiency roll-off,OLEDs
更新于2025-09-23 15:19:57
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Imidazo[1,2-a]pyridine as an electron acceptor to construct?? high-performance deep-blue organic light-emitting diodes with negligible efficiency roll-off
摘要： Two novel bipolar deep-blue fluorescent emitters, IP-PPI and IP-DPPI featuring different lengths of phenyl bridge, were designed and synthesized, in which imidazo[1,2-a]pyridine (IP) and phenanthroimidazole (PI) were proposed as an electron-acceptor and an electron donor respectively. Both of them exhibited outstanding thermal stability and high emission quantum yield. All the devices based on these two materials showed negligible efficiency roll-off with increasing current density. Impressively, non-doped organic light-emitting diodes (OLEDs) based on IP-PPI and IP-DPPI exhibited EQE of 4.85% and 4.74% with CIE coordinates of (0.153, 0.097) and (0.154, 0.114) at 10000 cd m-2, respectively. Besides, the 40 wt% IP-PPI doped device maintained high EQE of 5.23% with CIE coordinates of (0.154, 0.077) at 10000 cd m-2. The doped device based on 20 wt% IP-DPPI exhibited higher deep-blue electroluminescence (EL) performance with maximum EQE up to 6.13% at CIE of (0.153, 0.078) and remained EQE of 5.07% at 10000 cd m-2. To the best of our knowledge, these performances are among the state-of-the art devices with CIEy ≤ 0.08 at a high brightness of 10000 cd m-2. Furthermore, by doping a red phosphorescent dye Ir(MDQ)2 into IP-PPI and IP-DPPI hosts, high-performance red PhOLEDs with EQE of 20.8% and 19.1% were achieved, respectively. This work may provide a new approach for designing highly efficient deep-blue emitters with negligible roll-off for OLED applications.
关键词： negligible efficiency roll-off,imidazo[1,2-a]pyridine,OLEDs,deep-blue
更新于2025-09-23 15:19:57