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Tunable Emission of Bluish Zn-Cu-Ga-S Quantum Dots by Mn Doping and their Electroluminescence
摘要： Based on bluish-emitting double-shelled quantum dots (QDs) of Zn?Cu?Ga?S (ZCGS)/ZnS/ZnS, Mn doping into ZCGS host with different Mn/Cu concentrations is implemented via surface adsorption and lattice diffusion. The resulting double-shelled Mn-doped ZCGS (ZCGS:Mn) QDs exhibit a distinct Mn2+ 4T1?6A1 emission as a consequence of effective lattice incorporation simultaneously with host intragap states-involving emissions of free-to-bound and donor-acceptor pair (DAP) recombinations. The relative contribution of Mn emission in the overall photoluminescence (PL) is consistently proportional to its concentration, resulting in tunable PL from bluish, white, to reddish white. Regardless of Mn doping and its concentration all QDs possess high PL quantum yield (QY) levels of 74?79%. Those undoped and doped QDs are then employed as an emitting layer (EML) of all-solution-processed QD-light-emitting diodes (QLEDs) with hybrid charge transport layers and their electroluminescence (EL) is compared. When compared to undoped QDs, doped analogues give rise to a huge spectral disparity of EL versus PL, specifically showing a near-complete quenching of Mn2+ EL. This unexpected observation is rationalized primarily by considering unbalanced carrier injection to QD EML on the basis of energetic alignment of the present QLED and rapid trapping of holes injected at intragap states of QDs.
关键词： Tunable emission,Electroluminescence,Emission quenching,Zn?Cu?Ga?S quantum dots,Mn doping
更新于2025-11-20 15:33:11
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Utilization of Ternary Europium Complex for Organic Electroluminescent Devices and as a Sensitizer to Improve Electroluminescence of Red-Emitting Iridium Complex
摘要： Two new lanthanide complexes [Ln(hfaa)3(Py-Im)] [hfaa = hexafluoroacetylacetone, Py-Im = 2-(2-pyridyl)benzimidazole and Ln = Eu(III) (1) and Tb(III) (2)] were synthesized and characterized. An X-ray crystal structure determination confirms that complex 1 is eight-coordinate with a distorted trigonal dodecahedral geometry. It shows typical vivid red Eu(III) emission in the solid state, in solution, and in a polymer matrix. The observed lifetime (τobs) of complex 1 in the solid state, in dichloromethane (DCM) solution, and in thin films is 833.01, 837.95, and 626.16?715.69 μs, respectively, with a photoluminescence quantum yield QEuL ≈ 33% in DCM solution. Complex 2 displays a yellowish-green emission in the solid state (τobs ≈ 36.99 μs), while a near white-light emission in solution (x; 0.2574: y; 0.3371) and in thin films. Therefore, it is a potential candidate for generating single-component white light-emitting materials for solid-state lighting applications. The kinetic scheme for modeling energy-transfer processes shows that the main donor state for 1 is the ligand triplet state (T1) and that energy transfer occurs to both the 5D1 (56.55%) and 5D0 (40.58%) levels. We fabricated a series of single- and double-layer organic light-emitting devices using complex 1. The luminance of the optimized double-layer electroluminescence (EL) device was 373 cd/m2 with very low turn-on voltage of ～4.2 V. Complex 1 was further utilized as a sensitizer to improve the EL of a red-emitting iridium complex PQ2Ir(dpm) (PQ = phenylquinoly-N,C2′, dpm = dipivaloylmethane). The codoped device achieved a maximum brightness and maximum current efficiency (ηc) of 93 224 cd/m2 and 36.38 cd/A, respectively.
关键词： electroluminescence,organic light-emitting devices,photoluminescence,energy transfer,lanthanide complexes
更新于2025-11-20 15:33:11
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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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Role of interface potential barrier, Auger recombination and temporal coherence in In <sub/>0.5</sub> Ga <sub/>0.5</sub> As/GaAs quantum dot-based p-i-n light emitting diodes
摘要： In this work, we investigate the mechanisms that control the electroluminescence from p-i-n heterostructures containing self-assembled In0.5Ga0.5As quantum dots embedded inside a GaAs/Al0.3Ga0.7As quantum well as a function of temperature and applied bias. Our results reveal that the carrier dynamics at the interface between the quantum dot and the quantum well play a crucial role in the electroluminescence emission. At low temperatures, two distinct emission bands are observed. Initially at low bias current, we observe broad emissions from the quantum wells and wetting layers. Another dominant and sharp emission at lower energy arises from the quantum dots, but only at higher bias currents. We discuss how a potential barrier between the quantum dots and quantum well can control the density of injected carriers undergoing optical recombination. We have also investigated the role of carrier capture and escape, quantum-confined stark effect and band-filling effects in the electroluminescence emission. In addition, we demonstrate how measurements of temporal coherence of individual spectral peaks, can detect the presence of Auger recombination in quantum dots under high injection currents. Interestingly, a significant increase in the temporal coherence of quantum dot emissions is observed, which could be due to a decrease in Auger recombination with increasing temperature.
关键词： quantum dots,Auger recombination,electroluminescence,coherence
更新于2025-11-14 17:28:48
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Admittance of Organic LED Structures with an Emission YAK-203 Layer
摘要： The current-voltage characteristics and admittance of multilayer structures for organic LEDs based on the PEDOT:PSS/NPD/YAK-203/BCP system have been experimentally investigated in a wide range of the measurement conditions. It is shown that at voltages corresponding to the effective radiative recombination of charge carriers, a significant decrease in the differential capacitance of the structures is observed. The frequency dependences of the normalized conductance of LED structures are in good agreement with the results of numerical simulation in the framework of the equivalent circuit method. Changes in the frequency dependences of the admittance with a change in temperature are most pronounced in the temperature range of 200–300 K and less noticeable in the temperature range of 8–200 K. From the frequency dependences of the imaginary part of impedance, the charge carrier mobilities are found at various voltages and temperatures. The mobility values obtained by this method are somewhat lower than those determined by the transient electroluminescence method. The dependence of the mobility on the electric field is well approximated by a linear function. As the temperature decreases from 300 to 220 K, the mobility decreases several times.
关键词： frequency dependence of imaginary part of impedance,LED structure,current-voltage characteristic,transient electroluminescence,organic semiconductor,charge carrier mobility,method of equivalent circuits,admittance
更新于2025-11-14 17:28:48
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Ligand-assisted synthesis of monodispersed and small-sized ZnO nanoparticles and their application in electroluminescence device
摘要： ZnO nanoparticle thin film has been demonstrated to be the best electron transportation material in quantum dot-based light emitting diodes (QD-LEDs). Therefore, the synthesis of well-dispersed and size-controllable ZnO nanoparticles is highly desirable. In this work, we present a facile and reproducible approach for the controllable synthesis of well-dispersed and monodispersed ZnO nanoparticles by using short-chain ethanolamine as the capping agent. It was found that ethanolamine plays an important role in the synthesis of monodispersed ZnO nanoparticles by controlling the nucleation and growth process. As a result, well-dispersed and size-controllable ZnO nanoparticles can be obtained. Compared with ligand-free conventional methods, our ligand-assisted approach has a higher reproducibility and a better controllability. We notice that QD-LEDs based on ligand-assisted ZnO exhibit a superior electroluminescence (EL) performance than those of traditional ZnO.
关键词： nanoparticles,ZnO,QD-LEDs,electroluminescence
更新于2025-11-14 17:04:02
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Theoretical and experimental study of PTDPV optical and vibrational properties and its application in white electroluminescent blends
摘要： The polymer Poly[tris(2,5-bis(hexyloxy)-1,4-phenylenevinylene)-alt-(1,3-phenylenevinylene)] (PTDPV) has a broad range of visible emission extending from green to red, and thus may be useful for obtaining a white light emitting blend. Nevertheless, the amount of works found in the literature dealing with the optical emission properties of PTDPV is very small. In this work, we performed a study of the optical properties of this material using photoluminescence and of the vibrational properties using Raman and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. At the same time, we use the Density Functional Theory (DFT) method to calculate the optical, vibrational and molecular properties of PTDPV. We have obtained the best DFT results using a hybrid functional and a simple basis set (DFT / B3LYP and 6–31 g *), without addition of correction or polarization factors (+). To reach these conclusions, we compared the HOMO and LUMO values obtained via DFT with those found in the literature. Furthermore, the Raman and IR simulations obtained using this basis set were compared with the experimental results of the PTDPV, showing great agreement. From the vibrational modes obtained, it was possible, using the Lin model [1–3], based on the Franck Condon approximations, to reconstruct the photoluminescence spectrum of the PTDPV. Based on these reconstructed spectra, it was possible to establish the contribution of the different vibrational modes to the vibronic emissions of the photoluminescence spectrum. The quality of the reconstruction obtained with the DFT results and that obtained with the experimental ones are very close, showing the possibility of using in this reconstruction the calculated vibrational modes when the experimental ones are not available. To demonstrate the application of this material, PFO:PTDPV blends were prepared, with which white photoluminescence was obtained. OLEDs prepared with these blends, in suitable proportions, emitted white light using low excitation power, demonstrating the feasibility of using PTDPV in OLEDs for lighting, which could be prepared by solution on large areas.
关键词： Photoluminescence,Raman and FT-IR,DFT method,PTDPV polymer,White electroluminescence
更新于2025-11-14 15:19:41
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The Study of Electroluminescence and Reliability of Polyimide Films in High DC Fields
摘要： Electroluminescence (EL) intensity of the polyimide (PI) films was tested under dc high electric field by home-made experimental device. The results showed that the EL intensity of PI films increased along with the electric field. EL intensity is approximately to background intensity when the electric-field intensity was less than 2.00 MV/cm. EL intensity increases along with increasing the electric field when electric-field intensity greater than 2.00 MV/cm. When electric-field at 2.80 MV/cm, EL intensity increasing strongly suggests that the excitation process related to hot electrons accelerated by the field approaching a critical threshold. Meanwhile, this work elaborates a method to deal with identical samples get different experimental data by using Weibull distribution method, and the concept of the reliability was presented. The nine groups of EL experimental data were analyzed, and the result showed that the lifetime of mid-value (t = 164.9 min). Mid-value of the breakdown field is E = 2.76 MV/cm.
关键词： reliability,breakdown,Weibull distribution,electroluminescence,PI films
更新于2025-09-23 15:23:52
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Self-Powered Motion-Driven Triboelectric Electroluminescence Textile
摘要： In recent years, smart light emitting type electronic devices for wearable applications have been required to have flexibility and miniaturization, which limits the use of conventional bulk batteries. Therefore, it is important to develop a self-powered light emitting system. Our study demonstrates the potential of a new self-powered luminescent textile system that emits light driven by random motions. The device is a ZnS:Cu based textile motion-driven electroluminescent device (TDEL) fabricated onto the woven fibers of the ZnS:Cu embedded PDMS (Polydimethylsiloxane) composite. Triboelectrification, which raises a discontinuous electric field, is generated by the contact separation movement of the friction material. Therefore, light can be generated via triboelectrification by the mechanical deformation of the ZnS:Cu embedded PDMS composite. This study showed that the TDEL emitted light from the internal triboelectric field during contact and from the external triboelectric field during separation. Light was then emitted twice in a cycle, suggesting that continuous light can be emitted by various movements, which is a key step in developing self-powered systems for wearable applications. Therefore, this technology is a textile motion-driven electroluminescence system based on composite fibers (ZnS:Cu + PDMS) and PTFE fibers, and the proposed self-emitting textile system can be easily fabricated and applied to smart clothes.
关键词： woven structure,electroluminescence,motion-driven,luminescent textile,triboelectrification
更新于2025-09-23 15:23:52
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Single-Molecule Based Electroluminescent Device as Future White Light Source
摘要： During last two decades spectacular development of light emitting diodes (LEDs) has been achieved owing to their widespread application possibilities. However, traditional LEDs suffer from unavoidable energy loss due to the down conversion of photons, toxicity due to the involvement of rare-earth materials in their production, higher manufacturing cost, and reduced thermal stability that prevent them from all-inclusive applications. To address the existing challenges associated with current commercially available white LEDs, herein, we report on a broadband emission originating from an intrinsic lanthanide-free single-molecule based LED. Self-assembly of a butterfly-shaped strontium-based compound {[Sr(H2btc)2(MeOH)(H2O)2]·2H2O} (1) was achieved through the reaction of Sr(NO3)2 with a benzene-1,2,3-tricarboxylic acid hydrate (1,2,3-H3btc) under hydrothermal conditions. White LED based on this single molecule exhibited a remarkable broadband luminescent spectrum with Commission Internationale de l’Eclairage (CIE) coordinates at (0.33, 0.32) under 30 mA current injection. Such a broad luminescent spectrum can be attributed to the simultaneous existence of several emission lines originating from the intramolecular interactions within the structure. To further examine the nature of the observed transitions, density functional theory (DFT) calculations were carried out to explore the geometric and electronic properties of the complex. Our study thus paves the way toward a key step for developing a basic understanding and the development of high performance broadband light emitting devices with environment-friendly characteristics based on organic?inorganic supramolecular materials.
关键词： Electroluminescence,Photoluminescence,Single Molecule,WLEDs,Strontium
更新于2025-09-23 15:23:52