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Electrostatic potential dispersing pyrimidine-5-carbonitrile acceptor for high efficiency and long lifetime thermally activated delayed fluorescence organic light-emitting diodes
摘要： Pyrimidine-5-carbonitrile was developed as an electrostatic potential managing and strong acceptor moiety of thermally activated delayed fluorescence (TADF) emitters for high efficiency and long lifetime in devices. Two types of TADF emitters with the donor moiety extended from either the 2 or 4 position of the acceptor moiety were prepared to study the effect of the donor substitution position on the TADF characteristics of the TADF emitters. Comparison of the two types of TADF emitters suggested that the extension of the donor structure from the 4 position of the pyrimidine-5-carbonitrile acceptor is an effective way of enhancing the external quantum efficiency (EQE) and lifetime of the TADF devices. A high EQE of 19.8% and lifetime exceeding that of the state-of-the-art green TADF emitter were demonstrated using one of the pyrimidine-5-carbonitrile derived emitters through the uniformly distributed electrostatic potential.
关键词： organic light-emitting diodes,Pyrimidine-5-carbonitrile,thermally activated delayed fluorescence,electrostatic potential,high efficiency,long lifetime
更新于2025-09-16 10:30:52
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Photophysics and electroluminescence of red quantum dots diluted in a thermally activated delayed fluorescence host
摘要： A feasible, universal, and low-cost strategy for quantum dot light-emitting devices (QLEDs) was provided to significantly enhance the electroluminescent performances. The emissive layer consists of organic host materials and quantum dots (QDs), and then the efficient energy transfer process remarkably promotes the device performances. It is confirmed that a highly efficient QLED can be realized by a host–guest system without common hole transport layers. The red device based on the thermally activated delayed fluorescence host and QD guest achieved a peak external quantum efficiency of 7.4%. Further, by simply modifying PEDOT:PSS with poly(4-styrenesulfonic acid), the work-function can be easily elevated, accompanied with the boosted external quantum efficiency to 11.9%. It is believed that such performances originate simultaneously from reduced interfacial fluorescence quenching, elevated work-function and efficient F?rster resonance energy transfer in the host–guest system.
关键词： external quantum efficiency,electroluminescent performances,quantum dot light-emitting devices,QLEDs,thermally activated delayed fluorescence,F?rster resonance energy transfer,host–guest system
更新于2025-09-16 10:30:52
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Blue thermally activated delayed fluorescence emitters incorporating acridan analogues with heavy group 14 elements for high-efficiency doped and non-doped OLEDs
摘要： Deep-blue thermally activated delayed fluorescence (TADF) emitters are promising alternatives for conventional fluorescence and phosphorescence materials for practical application in organic light-emitting diodes (OLEDs). However, as appropriate bipolar hosts for deep-blue TADF-OLEDs are scarce, the development of efficient deep-blue TADF emitters that are applicable to both doped and non-doped systems is an urgent task. In this study, we developed a new family of blue TADF emitters that demonstrated high photoluminescence (PL) and electroluminescence (EL) quantum efficiencies in both doped and non-doped (neat) systems. Four new donor–acceptor (D–A)-type TADF molecules incorporating phenazasiline, phenazagermine, and tetramethylcarbazole as weak D units and phenothiaborin as a weak A unit were designed and synthesized. By varying the structural rigidity/flexibility as well as the electron-donating ability of the D units, the resulting photophysical and TADF properties of the D–A molecules could be systematically regulated. A comprehensive photophysical investigation revealed that phenazasiline and phenazagermine-based emitters concurrently exhibit blue TADF emissions (464–483 nm), high PL quantum efficiencies (≈100%), extremely fast spin-converting reverse intersystem crossing rates (>107 s?1), and suppressed concentration quenching. These fascinating features in conjunction produced high-performance doped and non-doped blue TADF-OLEDs. The doped and non-doped TADF-OLEDs using the phenazasiline-based emitter demonstrated extremely high maximum external EL quantum efficiencies (ηext) of 27.6% and 20.9%, with CIE chromaticity coordinates of (0.14, 0.26) and (0.14, 0.20), respectively. Further, ultra-low efficiency roll-off behavior for both the doped and non-doped devices was demonstrated by their ηext as high as 26.1% and 18.2%, respectively, measured at a practically high luminance of 1000 cd m?2.
关键词： phenazasiline,phenothiaborin,tetramethylcarbazole,thermally activated delayed fluorescence,OLEDs,phenazagermine,blue emitters
更新于2025-09-16 10:30:52
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Achieving high-performance phosphorescent organic light-emitting diodes using thermally activated delayed fluorescence with low concentration
摘要： We fabricated phosphorescent organic light-emitting diodes (PhOLEDs) using thermally activated delayed fluorescence (TADF) material 10,10'-(4,4'-sulfonylbis(4,1-phenylene)) bis(9,9-dimethyl-9,10-dihydroacridine) (DMAC-DPS) with low concentration, which showed better performance compared with 1,3-bis(carbazole-9-yl) benzene (mCP) based devices. When the concentration of DMAC-DPS was 1wt%, the driving voltage of the device was only 3.3 V at 1 000 cd/m2, and the efficiency and lifetime of the device were effectively improved compared with those of mCP based devices. The result indicated that DMAC-DPS could effectively improve the performance of phosphorescent devices. We believe that the better device performance can be attributed to the optimization of the energy transfer process in the emitter layer and lifetime of triplet excitons by DMAC-DPS. The study may provide a simple and effective strategy to achieve high-performance OLEDs.
关键词： DMAC-DPS,thermally activated delayed fluorescence,triplet excitons,energy transfer,phosphorescent organic light-emitting diodes
更新于2025-09-16 10:30:52
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Synthesis of acridone-naphthylamine derivative and its thermally-activated delayed fluorescence studies for application in OLEDs
摘要： Acridone (acceptor) and naphthylamine (donor) based Donor-Acceptor-Donor (D-A-D) compound (1) was synthesised, characterised and its thermally-activated delayed fluorescence (TADF) properties were studied in detail. Compound 1 is fluorescent and emits in the green region (550 nm). The energy gap between the ground and the lowest excited singlet (S1) state is estimated to be 2.55 eV. The energy gap between the CT singlet and triplet states (DEST) was found to be *0.3 eV. Small DES1-T1 is one of the important criteria for TADF to take place in a molecule and thus detailed photophysics has been studied. Transient lifetime measurements showed an increase in the fluorescence lifetime (s) on purging with N2, as compared with that in air-saturated solution, indicating the involvement of the triplet state in emission. Emission at 550 nm was also observed with a delay of 100 ls which corresponded to the delayed fluorescence in 1. The lifetime of TADF was found to be 176 ls. Applications of TADF materials in organic light-emitting devices (OLEDs) has gotten attention as TADF materials utilise the triplet excitons which helps in increasing internal quantum efficiency of device. Air-saturated based on 1 were fabricated and their intensity was found to be nearly as high as 17,000 Cd/m2 at 25 mA/cm2 which was comparable to many of the known TADF emitters.
关键词： Acridone,thermally activated delayed fluorescence,organic light-emitting devices
更新于2025-09-16 10:30:52
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Naphthyridine-based thermally activated delayed fluorescence emitters for highly efficient blue OLEDs
摘要： Two TADF emitters 2,7-di(9H-carbazole)-1,8-naphthyridine (Cz-ND) and 2,7-di(3,6-di-tert-butyl-9H-carbazole)-1,8-naphthyridine (tBuCz-ND) were designed and synthesized. Both of the emitters showed high thermal stabilities and strong blue emissions with high photoluminescence quantum yields, and also exhibited excellent TADF properties with small ?EST values. Consequently, blue organic light-emitting diodes (OLEDs) based on Cz-ND and tBuCz-ND were fabricated, which could achieve maximum external quantum efficiencies (EQEmax) of 15.3 and 20.9%, respectively. Moreover, the devices also exhibited relatively narrow band gaps at 79 and 75 nm with the CIE coordinates of (0.15, 0.17) and (0.15, 0.22), respectively.
关键词： OLED,blue emission,carbazole,thermally activated delayed fluorescence,naphthyridine
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
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All-solution processed inverted QLEDs with double hole transport layers and thermal activated delay fluorescent dopant as energy transfer medium
摘要： Highly efficient, all-solution processed inverted quantum dot light-emitting diodes (QLEDs) with high performance are demonstrated by employing poly(9-vinlycarbazole) (PVK) as additional hole transport layer (HTL) and doping it with a blue thermal activated delay fluorescent (TADF) material, 4,5-bis(carbazol-9-yl)-1,2-dicyanobenzene (2CzPN). This PVK: 2CzPN composite layer not only optimizes hole injection, but also utilizes the leaked electrons to enhance device luminance by energy transfer process from 2CzPN to quantum dots (QDs). These benefits enable a 20-fold increment for the device current efficiency (from 0.523 cd/A to 11 cd/A) and a 9.9-fold improvement for the maximum luminance (from 3220 cd/m2 to 35352 cd/m2), compared with those of the standard QLED with poly[(9, 9-dioctylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-butylphenyl) (TFB) single HTL. In comparison with the QLED with TFB/pristine PVK double HTLs, the device performance of the optimal QLED with PVK: 2CzPN additional HTL are still 40.8% and 61.7% higher in luminance and current efficiency, respectively.
关键词： Thermally activated delayed fluorescence,Quantum dot light-emitting diode,All-solution process,Energy transfer,Double hole transport layers,Inverted structure
更新于2025-09-12 10:27:22
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Facile structure-modification of xanthenone based OLED emitters exhibiting both aggregation induced emission enhancement and thermally activated delayed fluorescence
摘要： Four new donor-acceptor compounds were designed, synthesized and investigated by theoretical and experimental approaches aiming to estimate effect of the structure of a donor on the properties of potential OLED emitters. Because of the different electron-donating abilities of the nitrogen-containing heterocycles, derivatives of xanthenone containing di-tert-butyl-carbazolyl, di-tert-butyl-acridanyl, di-tert-butyl-phenothiazinyl and penoxazinyl moieties exhibited different photophysical behavior. Because of big dihedral angles between the donors and acceptor as well as because of possibility of rotation around N-C bond, the designed compounds were characterized by thermally activated delayed fluorescence and aggregation induced emission enhancement effect. Twice higher photoluminesce quantum yields reaching 38% in doped films were obtained for compounds containing di-tert-butyl-carbazolyl and di-tert-butyl-acridanyl moieties as compared to those observed for compounds with the donors containing S and O heteroatoms. Strong effect of the donor substituents on charge injection (ionization potentials were in the range of 5.67-5.96 eV) and charge-transporting properties (hole and electron mobilities were in a wide range from 6.3×10-8 to 6.3×10-4 cm2V-1s-1 at electric field of 2.5×105 V·cm-1) was detected. The differently substituted compounds were utilized as emitters in OLEDs. Higher maximum values of external quantum efficiency (up to 3.5%) were observed for OLEDs based on emitters with nitrogen containing donors relative to estimated for OLEDs based on emitters containing di-tert-butyl-phenothiazinyl and penoxazinyl moieties.
关键词： aggregation induced emission enhancement,xanthenone,Organic light-emitting diode,thermally activated delayed fluorescence
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