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Dispirocycles: Novel Platforms for Construction of High-Performance Host Materials for Phosphorescent Organic Light-Emitting Diodes
摘要： Spirocycle compounds such as 9,9′-Spirobifluorene (SBF) are becoming more and more attractive for use as the host materials in organic optoelectronic devices. In this manuscript, two dispirocycles, namely dispiro[fluorene-9,9?-anthracene-10?,9??-fluorene] and 10,10??-diphenyl-10H,10??H-dispiro[acridine-9,9?-anthracene-10?,9??-acridine] were used for the construction of hosts materials (1, 2, 3, and 4). The attached triphenylamine group would determine the thermal, photophysical, electrochemical, and charge transport properties, and therefore they have different electroluminescence performances. The device based on dispiro[fluorene-9,9?-anthracene-10?,9??-fluorene] (2) and 10,10??-diphenyl-10H,10??H-dispiro[acridine-9,9?-anthracene-10?,9??-acridine] (3) molecular platforms exhibited a external quantum efficiency of over 21% with a very high power efficiency (~100 lm W-1). The results here demonstrate to us the potential of extending the possibilities of applying the dispirocyclic molecular platforms with inherent rigidity for developing highly efficient host materials for OLEDs.
关键词： Dispirocycles,OLEDs,Host materials,Phosphorescence,Triplet energy
更新于2025-11-19 16:56:42
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A bipolar deep blue-emitting fluorescent material based on imidazole and triphenylamine for efficient non-doped OLEDs
摘要： A bipolar deep blue-emitting fluorescent material, 1-(4-tert-butyl phenyl)-2-[4-(N,N- diphenyl)phenyl]-4,5-diphenyl-1H-imidazole (TPA-PIM) has been designed and synthesized for efficient blue organic light-emitting diodes (OLEDs). The photophysical, thermal and electrochemical properties of TPA-PIM are investigated. TPA-PIM possesses high thermal stabilities with decomposition temperature of 396 °C and shows a strong deep-blue emission at 407 nm in N, N-dimethylformamide (DMF) solution. Single-carrier devices are fabricated to show that TPA-PIM has good bipolar characteristics. The non-doped fluorescent OLEDs using TPA-PIM as emitter exhibited stable and efficient deep-blue emissions with the CIE coordinates of (0.16, 0.09), the maximum luminance of 1392 cd m?2 and the maximum current efficiency of 2.60 cd A?1.
关键词： Triphenylamine,Blue light-emitting materials,Bipolar materials,Imidazole,Non-doped OLEDs
更新于2025-11-19 16:56:42
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Light-Emitting Porphyrin Derivative Obtained from a Subproduct of the Cashew Nut Shell Liquid: A Promising Material for OLED Applications
摘要： In this work, the meso-tetra[4-(2-(3-n-pentadecylphenoxy)ethoxy]phenylporphyrin (H2P), obtained from the cashew nut shell liquid (CNSL), and its zinc (ZnP) and copper (CuP) metallic complexes, were applied as emitting layers in organic light emitting diodes (OLEDs). These compounds were characterized via optical and electrochemical analysis and the electroluminescent properties of the device have been studied. We performed a cyclic voltammetry analysis to determine the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energy levels for the porphyrins, in order to select the proper materials to assemble the device. H2P and ZnP presented fluorescence emission band in the red region, from 601 nm to 718 nm. Moreover, we verified that the introduction of bulky substituents hinders the π–π stacking, favoring the emission in the film. In addition, the strongest emitter, ZnP, presented a threshold voltage of 4 V and the maximum irradiance of 10 μW cm?2 with a current density (J) of 15 mA cm?2 at 10 V. The CuP complex showed to be a favorable material for the design of OLEDs in the infrared. These results suggest that the porphyrins derived from a renewable source, such as CNSL, is a promising material to be used in organic optoelectronic devices such as OLEDs.
关键词： cashew nut shell liquid,porphyrins,OLEDs,electroluminescence,photoluminescence
更新于2025-11-19 16:46:39
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Electrical and optical properties of organic light-emitting diodes with rhenium(I) complexes using DC and AC methods
摘要： Four rhenium(I) tricarbonyl complexes with 1,10-phenanthroline and derivative bearing electron-donating CH3 and OCH3 substituents were doped into host material poly (9-vinylcarbazole) (PVK) with a mass ratio of 8% as the emissive layer in organic light-emitting diodes (OLEDs). All complexes showed photoluminescence in the solution and embedded into a PVK matrix (λmax～520–550 nm). The comparison with the bare PVK emission and the compound/PVK ?lm shows that the emission of the polymer was quenched through an energy transfer process from PVK to the dopant. The electrical properties of the devices with FTO/PEDOT:PSS/Complex:PVK/Al architecture were investigated using the DC method by curves of current density-voltage and the AC method as admittance spectroscopy, which showed that the behavior of the devices is controlled by charge carrier injection rather than bulk transport.
关键词： Energy transfer,Re(I) complexes,Charge injection,Admittance spectroscopy,Emission,OLEDs
更新于2025-11-14 17:28:48
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Blue-green-emitting cationic iridium complexes with oxadiazole-type counter-anions and their use for highly efficient solution-processed organic light-emitting diodes
摘要： Cationic iridium complexes are promising phosphorescent dopants for solution-processed organic light-emitting diodes (OLEDs) and counter-anion control has emerged as a facile approach to tailor their properties for high-performance devices. A series of oxadiazole-type anions, 3-(5-phenyl-1,3,4-oxadiazol-2-yl)benzenesulfonate (OXD-SO3?), 3-(5-(4-(tert-butyl)phenyl)-1,3,4-oxadiazol-2-yl)benzenesulfonate (tBuOXD-SO3?) and (3-(5-(4-(tert-butyl)phenyl)-1,3,4-oxadiazol-2-yl)phenyl)trifluoroborate (tBuOXD-BF3?), have been prepared as counter-anions for blue-green-emitting cationic iridium complexes. The photophysical and electrochemical properties of the anions and the complexes have been comprehensively characterized. The anions do not affect the emission properties of the phosphorescent cation and efficiently transfer their energy to the cations in films. Solution-processed, double-layer OLEDs using the complexes as dopants have shown much higher (～1.4) efficiencies than the device using the reference complex with a PF6? counter-anion, owing to the improvement of carrier transport/recombination balance by the electron-trapping effect of oxadiazole-type anions. In particular, the blue-green device using the complex with the OXD-SO3? counter-anion affords a peak current efficiency of 37.6 cd A?1 and a peak external quantum efficiency (EQE) of 15.2%, which is the highest for solution-processed OLEDs based on cationic iridium complexes reported so far.
关键词： solution-processed OLEDs,oxadiazole-type counter-anions,phosphorescent dopants,cationic iridium complexes,high-performance devices
更新于2025-11-14 15:23:50
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Effect of exciton diffusion on the triplet-triplet annihilation rate in organic semiconductor host-guest systems
摘要： We study the contribution of triplet exciton diffusion to the efficiency loss resulting from F?rster-type triplet-triplet annihilation (TTA) in organic phosphorescent semiconductor host-guest systems, using kinetic Monte Carlo (KMC) simulations. Our study focusses on diffusion due to F?rster-type guest-guest transfer, but includes also a comparison with simulation results for the case of Dexter-type guest-guest transfer. The simulations are carried out for a wide range of F?rster radii, and for guest concentrations up to 100 mol%, with the purpose to support analyses of time-resolved photoluminescence experiments probing TTA. We find that the relative contribution of diffusion to the TTA-induced efficiency loss may be deduced quite accurately from a quantitative experimental measure for the shape of the time-dependent photoluminescence intensity, the so-called r ratio. For small guest concentrations and F?rster radii that are most relevant to organic light-emitting diodes (OLEDs), the diffusion contribution is in general quite small. Under these weak-diffusion conditions, the absolute diffusion contribution to the TTA-induced efficiency loss can be understood quantitatively using a capture radius formalism. The effective guest-guest diffusion coefficient that follows from the TTA simulations, using the capture radius formalism, agrees well with the diffusion coefficient that follows from direct KMC diffusion simulations. The simulations reveal that the diffusion coefficient is strongly affected by the randomness of the distribution of guest molecule locations.
关键词： OLEDs,photoluminescence,kinetic Monte Carlo simulations,Dexter transfer,organic semiconductors,triplet-triplet annihilation,exciton diffusion,host-guest systems,F?rster transfer
更新于2025-09-23 15:23:52
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Circularly Polarized Luminescence from Chiral Conjugated Poly(carbazole-ran-acridine)s with Aggregation-Induced Emission and Delayed Fluorescence
摘要： Pure organic materials with circularly polarized luminescence (CPL) and delayed fluorescence have gained increasing interest from academic and technological areas. To enhance the solid-state emission and exciton utilization in chiral optoelectronic devices, a synthetic strategy to impart conjugated polymers with CPL and aggregation-induced delayed fluorescence was proposed. Herein, two conjugated macromolecules with electron-donating poly(carbazole-ran-acridine) backbones, electron-withdrawing dibenzothiophen-2-yl(phenyl)methanone and chiral alanine moieties were designed and synthesized. Their neat films exhibited strong green emission with quantum yields of 6.7% and 10.3% and delayed fluorescence with lifetime of 1.358 μs and 1.366 μs, respectively. Both Cotton effect and CPL with dissymmetry factor of –2.01 × 10–3 and –1.39 × 10–3 were determined in the solid state. Such unique conjugated polymers were employed as solution-processed emitting layers in organic light emitting diodes, which displayed maximum brightness of 1477 cd/m2 and maximum current efficiency of 2.52 cd/A.
关键词： OLEDs,conjugated polymers,aggregation-induced emission,delayed fluorescence,aggregation-induced delayed fluorescence,circularly polarized luminescence
更新于2025-09-23 15:23:52
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Lanthanide complexes with 2-(tosylamino)-benzylidene-N-(aryloyl)hydrazones - universal luminescent materials
摘要： Lanthanide complexes Ln(L1)(HL1) (Ln = Lu, Yb, Er, Gd, Eu, Sm) and Ln(L2)(HL2) (Ln = Lu, Yb, Gd, Eu) with 2-(tosylamino)-benzylidene-N-(aryloyl)hydrazones (H2L1, aryloyl = 2-hydroxybenzoyl; H2L2, aryloyl = Isonicotinoyl) were obtained with the aim to explore them as new luminescent materials. They were found to form monomeric species independently on the aryloyl nature, their crystal structures were determined from single crystal X-ray data (Yb(L2)(HL2)·0.5(C2H5OH)), as well as from powder X-ray data by Rietveld refinement (Eu(L1)(HL1)). Ytterbium complexes exhibited intense luminescence, which allowed using them in host-free OLEDs, which demonstrated remarkable efficiency of NIR electroluminescence (50 μW/W) at low voltage (5V). Special mechanism of europium luminescence quenching allowed using europium complexes as luminescent thermometers, which demonstrated very high sensitivity up to 12%/K. The theory of luminescence thermometry based on three-level system was proposed which allowed predicting sensitivity with high accuracy (error within 20%).
关键词： lanthanide complexes,OLEDs,luminescent thermometry,NIR emission,luminescent materials
更新于2025-09-23 15:23:52
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Monodisperse Six-Armed Starbursts based on Truxene-Cored Multibranched Oligofluorenes: Design, Synthesis, and Stabilized Lasing Characteristics
摘要： A series of monodisperse six-armed conjugated starbursts (Tr1F, Tr2F and Tr3F) containing a truxene core and multibranched oligofluorene bridges capped with diphenylamine (DPA) units has been designed, synthesized, and investigated as robust gain media for organic semiconductor lasers (OSLs). The influence of electron-rich DPA end-groups on their optoelectronic characteristics has been discussed at length. DPA cappers effectively raise HOMO levels of the starbursts, thus enhancing the hole injection and transport ability. Solution-processed electroluminescence devices based on the resulting six-armed starbursts exhibited efficient deep-blue electroluminescence with clear reduced turn-on voltages (3.2~3.5 V). Moreover, the resulting six-armed molecules showed stabilized electroluminescence and amplified spontaneous emission with low thresholds (27.4~63.9 nJ pulse-1), high net gain coefficients (80.1~101.3 cm-1), and small optical loss (2.6~4.4 cm-1). Distributed feedback OSLs made from Tr3F exhibited low lasing threshold of 0.31 kW/cm2 (at 465 nm). The results suggest that the construction of truxene-centered six-armed conjugated starbursts with the incorporation of DPA units can effectively enhance EL properties by precisely regulating the HOMO energy levels, and further optimizing their optical gain properties.
关键词： Organic gain media,Organic light-emitting diodes (OLEDs),Conjugated starburst molecules,Organic semiconductor lasers (OSLs),HOMO levels
更新于2025-09-23 15:22:29
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[SpringerBriefs in Applied Sciences and Technology] Air-Stable Inverted Organic Light-Emitting Diodes ||
摘要： We introduce the importance of air stability on the basis of the principles and the history of organic light-emitting diodes (OLEDs), and the way of realising air-stable OLEDs finally. OLEDs are current-driven self-emitting devices that, in principle, have the features of lightness and thinness. Therefore OLEDs are expected to have unprecedented flexibility. However, it is difficult to achieve air stability in OLEDs, which is the key property for the realisation of flexible devices, because it has been essential to use air-active materials in consideration of the operational mechanism.
关键词： organic electronics,air stability,OLEDs,encapsulation,flexibility
更新于2025-09-23 15:21:01