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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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A simple and green synthesis of carbon quantum dots from coke for white light-emitting devices
摘要： Coke is a by-product of coal. This paper reports a simple and green chemical oxidation method for carbon quantum dots (CQDs) from coke for use in novel applications. The CQDs emit blue fluorescence and have a fluorescence quantum yield of 9.2% and blue-green-red spectral composition of 48%. A light-emitting diode (LED) was fabricated by combining the CQDs as a white-light converter with an ultraviolet chip. The Commission Internationale de L'Eclairage chromaticity coordinate (0.31, 0.35) and correlated color temperature (5125 K) of the LED are located in a cool white light zone, suggesting that they have superior potential application in lighting devices.
关键词： carbon quantum dots,white light-emitting devices,fluorescence,coke,chemical oxidation
更新于2025-09-16 10:30:52
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Synthesis and properties of hyperbranched polymers for white polymer light-emitting diodes
摘要： In this work, a series of hyperbranched copolymers with fluorene-alt-carbazole as the branches, three-dimensional-structured spiro[3.3]heptane-2,6-dispirofluorene (SDF) as the core, and iridium 1-(4-bromophenyl)-isoquinoline (acetylacetone) (Ir(Brpiq)2acac) as the dimming group were synthesized by one-pot Suzuki polycondensation for white emission. All copolymers show great thermal stabilities and high hole-transporting ability due to the introduction of the carbazole unit. The hyperbranched structures for copolymers can suppress the interchain interactions efficiently, and help to form amorphous films. The fabricated polymer light-emitting devices (PLEDs) based on the above synthesized copolymers realize good white light emission, and achieve high electroluminescence (EL) performance. For example, for the optimized PLED, the maximum luminance and current efficiency reach 6210 cd m?2 and 6.30 cd A?1, respectively, indicating the synthesized hyperbranched copolymers have potential application in solution-processable white polymer light-emitting diodes.
关键词： hyperbranched copolymers,electroluminescence,white emission,Suzuki polycondensation,polymer light-emitting devices
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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Perovskite quantum dots for light-emitting devices
摘要： Perovskite quantum dots (QDs) have been hotly pursued in recent decades owing to their quantum confinement effect and defect-tolerant nature. Their unique optical properties, such as high photoluminescence quantum yield (PLQY) approaching unity, narrow emission bandwidth, tunable wavelength spanning the entire visible spectrum, and compatibility with flexible/stretchable electronics, render perovskite QDs promising for next-generation solid lighting sources and information displays. Herein, the advances in perovskite QDs and their applications in LEDs are reviewed. Strategies to fabricate efficient perovskite QDs and device configuration, including material composition design, synthetic methods, surface engineering, and device optimization, are investigated and highlighted. Moreover, the main challenges in perovskite QDs of instability and toxicity (lead-based) are identified, while the solutions undertaken with respect to composition engineering, device encapsulation, and lead-replacement QDs are demonstrated. Meanwhile, perspectives for the further development of perovskite QDs and corresponding LEDs are presented.
关键词： device encapsulation,quantum confinement,Perovskite quantum dots,LEDs,instability,composition engineering,flexible electronics,photoluminescence,lead-replacement,stretchable electronics,toxicity,light-emitting devices
更新于2025-09-16 10:30:52
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Analysis of electroluminescence spectra from high optical-power density forward-biased silicon-led in standard CMOS technology
摘要： A Si-LED with high-power density p+-n junction and wedge-shaped electrodes was fabricated by standard complementary metal oxide-semiconductor (CMOS) process, and its electroluminescence (EL) spectra were measured at different forward currents. By studying the EL spectra, two interesting phenomena were found. One was that the main peak of EL spectra transited from long wavelength (1135 nm) to short wavelength (1078 nm) along with the forward current increased. The other was that two light emission peaks with energy larger than band gap (Eg) were observed. For the first time, reasonable explanations to the two phenomena were given. Here, the peak shift is attributed to that, with forward current increased, the electron-hole pair recombination of the bound excitons without assist of phonons, increases faster than that of those bound or free excitons with assist of phonons. And the existence of two energy-high light emission peaks is resulted from that, under strong electric field, hot holes absorb one or two phonons from the crystal lattice and then recombine with electrons in conduction band.
关键词： Wedge-shaped pinpoint electrode,CMOS standard technology,Electroluminescence (EL) spectra,Silicon-based light-emitting devices (Si-LEDs),Strong electric field
更新于2025-09-12 10:27:22
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Luminescent Copper(I) complexes as promising materials for the next generation of energy-saving OLED devices
摘要： The increasing demand for electrical energy by a longer living and increasing population justifies the search for new, more efficient lighting systems. In this context, organo-metallic compounds have been largely investigated as efficient materials for organic light emitting diodes (OLEDs). Special interest has been demonstrated for neutral copper(I) complexes due to their high emission quantum efficiency and fast photoluminescence response time. In particular, Cu(I) complexes that present thermally activated delayed fluorescence (TADF) are one of the most promising materials for the next generation of lighting devices. In this work, we present an overview of the development of OLEDs, by comparing the mechanisms and efficiencies of different complexes and discussing the reasons why Cu(I) complexes have potential to be one of the most efficient alternatives for energy saving in lighting.
关键词： TADF,Cu(I) complexes,Light emitting devices,OLED
更新于2025-09-12 10:27:22
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Advances in Inkjet‐Printed Metal‐Halide Perovskite Photovoltaic and Optoelectronic Devices
摘要： Inkjet-printing (IJP) has evolved over the last 30 years into a reliable, versatile and cost-effective industrial production technology in many areas from graphics to printed electronic applications. Intensive research efforts have led to the successful development of functional electronic inks to realize printed circuit boards, sensors, lighting, actuators, energy storage and power generation devices. Recently, a promising solution-processable material class has entered the stage: metal halide perovskites (MHP). Within just ten years of research, the efficiency of perovskite solar cells (PSCs) on a laboratory scale increased to over 25%. Despite the complex nature of MHPs, significant progress has also been made in controlling film formation in terms of ink development, substrate wetting behavior and crystallization processes of inkjet-printed MHPs. This results in highly efficient inkjet-printed PSCs with a PCE of almost 21%, paving the way for cost-effective and highly efficient thin film solar cell technology. In addition, the excellent optoelectronic properties of inkjet-printed MHPs achieve remarkable results in photodetectors, X-ray detectors and illumination applications. This manuscript provides a comprehensive overview of the state of the art and recent advances in the production of inkjet-printed MHPs for highly efficient and innovative optoelectronic devices.
关键词： additive manufacturing,optoelectronic,perovskite,inkjet printing,light emitting devices,solar cells
更新于2025-09-11 14:15:04
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Optical and Structural Characteristics of CdSe/PMMA Nanocomposites
摘要： Nanocomposites of polymethylmethacrylate (PMMA) and CdSe were fabricated by a casting technique. The result showed that CdSe@PMMA can be used in white and green light emitting devices. 0.01CdSe@PMMA exhibits monochromatic green color emission with the highest fluorescent quantum yield and lowest optical band gap value, while CdSe@PMMA with other ratios shows a multicolor emission. The band-edge emits in the vicinity of 280 – 296 nm but a more stable intensive green color emission at 553 nm is found for 0.01CdSe@PMMA. The change in Eg (4.18 to 4.4) eV values is due to the interaction between the PMMA polymer and CdSe.
关键词： nanocomposites,optical properties,PMMA,light emitting devices,CdSe
更新于2025-09-10 09:29:36
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Triarylboryl-substituted carbazoles as bipolar host materials for efficient green phosphorescent organic light-emitting devices
摘要： Two novel bipolar host materials based on carbazole and triarylborane moieties, i.e. B-2CZ and m-B-CZ, are synthesized and characterized. The spatially crowded compound B-2CZ exhibits a high thermal stability (Td > 340 °C) compared to the reported triarylboryl carbazoles, presumably due to the highly compact architecture. As a result, phosphorescent Ir(ppy)3 combined with both the borylated compounds is selected to construct a host-guest system. Devices A (B-2CZ) and B (m-B-CZ) achieve peak efficiencies of 19.3% (69.1 cd/A and 88.1 lm/W) and 19.1% (66.1 cd/A and 77.2 lm/W), respectively. The respective turn-on voltages of devices A and B are recorded at 2.4 and 2.6 V, which are much lower than that of device with the benchmark host (mCP, 3.3 V). In addition, at a higher practical luminance of 100 cd/m2 (1000 cd/m2), the external quantum efficiencies of devices A and B are still preserved at 19.1% (17.3%) and 18.2% (13.0%) with the mitigated efficiency drops of 1% (10%) and 5% (32%), suggesting the promising advantage for realizing efficient phosphorescent organic light-emitting devices.
关键词： Carbazole,Triarylborane,Bipolar host,Phosphorescent organic light-emitting devices
更新于2025-09-10 09:29:36