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Highly efficient rare-earth-free deep red emitting phosphor La <sub/>2</sub> Li <sub/>1?y</sub> Sb <sub/>1?x</sub> O <sub/>6</sub> : <i>x</i> Mn <sup>4+</sup> , <i>y</i> Mg <sup>2+</sup> : application in high-power warm w-LEDs
摘要： Phosphor-in-glass (PiG), which serves as both a luminescent convertor and organic encapsulation material in high-power white light-emitting diodes (w-LEDs), has become a prospective research hotspot owing to its high transparency and thermal stability. However, YAG:Ce3+ PiG-based LED devices still suffer from a lack of a red component. Therefore, the development of red phosphors with excellent quantum efficiency and superior thermal stability is urgent. Herein, a highly efficient La2Li1?ySb1?xO6:xMn4+,yMg2+ red phosphor with a broadband emission ranging from 670 to 720 nm was fabricated via a conventional solid-state reaction. By co-doping Mg2+ in La2LiSbO6:Mn4+, the emission intensity was enhanced significantly, which reaches as high as 10 times that of the single-doped La2LiSbO6:Mn4+. It is proposed that the Mg2+ dopant can compensate imbalanced charges for the substitution of Sb5+ by Mn4+ and interrupt adverse energy transfer among the Mn4+ activators. Impressively, a maximum quantum yield of up to 80.3% is achieved and about 80% emission intensity is retained at the temperature of 423 K. Furthermore, the crystal field strength (Dq) and Racah parameters (B and C) together with the nephelauxetic ratio (b1) were calculated based on the obtained spectroscopic data. By embedding the red-emitting La2LiSbO6:Mn4+,Mg2+ phosphor and yellow-emitting YAG:Ce3+ phosphor into TeO2-based glass, an inorganic PiG composite as a color converter to replace organic silicone was acquired. The excellent optical parameters and tunable chromaticity feature of the fabricated w-LEDs were achieved by adjusting the mass ratio of La2LiSbO6:Mn4+,Mg2+ to YAG:Ce3+ in the PiG plate, where the correlated color temperature changed from cool white (6555 K) to warm (4130 K) and the color rendering index increased from 73.7 to 86.6 under an operating current of 300 mA.
关键词： Phosphor-in-glass,quantum yield,red phosphor,Mg2+,thermal stability,w-LEDs,Mn4+
更新于2025-11-20 15:33:11
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Rational design of a visible-light photochromic diarylethene: a simple strategy by extending conjugation with electron donating groups
摘要： Photochromic diarylethenes have been widely used in many fields. However, their cyclization process must be induced by UV light. In this article, a simple strategy is developed by extending π-conjugation with electron donating groups. The modified dirylethene derivative can photocyclolize under 405-nm light with a good photochromic efficiency. Meanwhile, its absorption and moderate fluorescence can be switched effectively in both directions by visible lights (405 and 520 nm, respectively) in different solutions and in living cells. We believe that this simple method will become a versatile strategy for developing various dirylethylenes with visible-light photochromism.
关键词： fluorescence photoswitching,diarylethylenes,photoreaction quantum yield,visible-light photochromism
更新于2025-11-19 16:56:35
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Solar water splitting over Rh <sub/>0.5</sub> Cr <sub/>1.5</sub> O <sub/>3</sub> -loaded AgTaO <sub/>3</sub> of a valence-band-controlled metal oxide photocatalyst
摘要： Improvement of water splitting performance of AgTaO3 (BG 3.4 eV) of a valence-band-controlled photocatalyst was examined. Survey of cocatalysts revealed that a Rh0.5Cr1.5O3 cocatalyst was much more effective than Cr2O3, RuO2, NiO and Pt for water splitting into H2 and O2 in a stoichiometric amount. The optimum loading amount of the Rh0.5Cr1.5O3 cocatalyst was 0.2 wt%. The apparent quantum yield (AQY) at 340 nm of the optimized Rh0.5Cr1.5O3(0.2 wt%)/AgTaO3 photocatalyst reached to about 40%. Rh0.5Cr1.5O3(0.2 wt%)/AgTaO3 gave a solar to hydrogen conversion efficiency (STH) of 0.13% for photocatalytic water splitting under simulated sunlight irradiation. Bubbles of gasses evolved by the solar water splitting were visually observed under atmospheric pressure at room temperature.
关键词： Rh0.5Cr1.5O3 cocatalyst,valence-band-controlled photocatalyst,solar water splitting,apparent quantum yield,AgTaO3,solar to hydrogen conversion efficiency
更新于2025-11-19 16:51:07
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Quantum Yield Enhancement in Graphene Quantum Dots via Esterification with Benzyl Alcohol
摘要： The quantum yield of graphene quantum dots was enhanced by restriction of the rotation and vibration of surface functional groups on the edges of the graphene quantum dots via esterification with benzyl alcohol; this enhancement is crucial for the widespread application of graphene quantum dots in light-harvesting devices and optoelectronics. The obtained graphene quantum dots with highly graphene-stacked structures are understood to participate in π–π interactions with adjacent aromatic rings of the benzylic ester on the edges of the graphene quantum dots, thus impeding the nonradiative recombination process in graphene quantum dots. Furthermore, the crude graphene quantum dots were in a gel-like solid form and showed white luminescence under blue light illumination. Our results show the potential for improving the photophysical properties of nanomaterials, such as the quantum yield and band-gap energy for emission, by controlling the functional groups on the surface of graphene quantum dots through an organic modification approach.
关键词： Optoelectronics,Esterification,Quantum yield,Benzyl alcohol,Graphene quantum dots
更新于2025-11-19 16:46:39
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Tunable Photophysical Properties of Thiophene Based Chromophores: Conjoined Experimental and Theoretical Investigation
摘要： In this paper we report synthesis and photophysical properties of six novel thiophene derivatives (ThD) with D-π-A structure. The subject of this work are three nitrophenyls (1) BT-Th-NO2 and three benzonitriles (2) BT-Th-CN, substituted at different positions of aromatic ring ((a) ortho-, (b) meta- or (c) para-). Dyes were obtained using simple three-step synthesis and their chemical structures were confirmed by 1H and 13C NMR, IR as well as high resolution mass spectrometry. The influence of positional isomerism on optical properties has been explored experimentally and theoretically. The photophysical properties were investigated using steady-state as well as time-resolved spectroscopy and the obtained results were supported by quantum-chemical calculations. TD-DFT calculations indicated that charge-transfer strength can be correlated with the observed optical properties. In addition, the influence of the acceptor position on photoluminescence spectra, fluorescence quantum yields and emission lifetimes was specified. We show that ThD optical properties can be tuned in wide spectral range by the change made in only single step of synthesis reaction.
关键词： push-pull chromophores,Thiophene derivatives,TD-DFT,quantum yield,charge transfer
更新于2025-11-19 16:46:39
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Increasing photoluminescence quantum yield by nanophotonic design of quantum-confined halide perovskite nanowire arrays
摘要： High photoluminescence quantum yield (PLQY) is required to reach optimal performance in solar cells, lasers and light-emitting diodes (LEDs). Typically, PLQY can be increased by improving the material quality to reduce the non-radiative recombination rate. It is in principle equally effective to improve the optical design by nanostructuring a material to increase light out-coupling efficiency and introduce quantum confinement, both of which can increase the radiative recombination rate. However, increased surface recombination typically minimizes nanostructure gains in PLQY. Here a template guided vapor phase growth of CH3NH3PbI3 (MAPbI3) nanowire (NW) arrays with unprecedented control of NW diameter from the bulk (250 nm) to the quantum confined regime (5.7 nm) is demonstrated, while simultaneously providing a low surface recombination velocity of 18 cm s-1. This enables a 56-fold increase in the internal PLQY, from 0.81 % to 45.1 %, and a 2.3-fold increase in light out-coupling efficiency to increase the external PLQY by a factor of 130, from 0.33 % up to 42.6 %, exclusively using nanophotonic design.
关键词： light out-coupling,photoluminescence quantum yield,quantum confinement,perovskite,photodetector
更新于2025-11-14 15:28:36
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Rapid preparation of homogeneous carbon dots with yellow fluorescence and formation mechanistic investigation
摘要： In this study, homogeneous carbon dots with yellow fluorescence and high absolute fluorescence quantum yields (78.6%) were firstly prepared through a one-step solvothermal method without complicated process of separation, in which sodium citrate, carbamide, and anhydrous calcium chloride were adopted as precursors, while toluene was selected as solvent. The as-prepared carbon dots with an average size of 5.9 nm have a high degree of crystallinity. According to the discussion of the formation mechanism carbon dots, it is found that the toluene guarantee the formation of crystalline core and Ca2+ promotes the formation of carbonaceous core with high crystallinity, which is responsible for the ultrahigh quantum yield. Furthermore, the fluorescent properties of carbon dots are excellent in organic solvents and could be quenched by water, making them a promising material used without any modification in the detection of water in organic solvents, which has a great influence on organic chemical reaction, and may even determine the resultant, yield, and selectivity of organic reaction.
关键词： Detection of water content,Ultrahigh quantum yield,Yellow fluorescence,Carbon dots,Quantum dot
更新于2025-11-14 15:28:36
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Synthesis of near unity photoluminescence CdSeTe alloyed Quantum Dots
摘要： Quantum dots (QD) tend to exhibit low photoluminescence (PL) properties due to long hanging ligands on their surface and steric barriers resulting therefrom. On the other hand, in order to be used in QD LED and QDSSC technologies, highly intense PL characteristics and PL lifetime are required respectively. Therefore, this study focuses on increasing the PL QY and PL lifetime of CdSeTe alloy QDs. To achieve this aim, CdSeTe alloy QDs synthesized by organometallic method were treated with different mass % (m/m) chloride solution. The PL Quantum Yield (PL QY) of CdSeTe alloy QDs, which was 13.2 ± 2.0% before treatment, increased to 97.4 ± 2.0% after treatment with 60% CdCl2 solution approaching to almost unity value. In addition to the increase in PL QY, PL lifetime increased from 28 ns to 33 ns with chloride treatment. However, thanks to surface passivation, the time to fall to half the value of PL QY for treated CdSeTe(Cl) QDs under oxygen exposure was increased from 10 h to 64 h. In the study, the absorbance and emission characterizations of CdSeTe alloy QDs treated with chloride and untreated, were presented.
关键词： Quantum dot,Photo luminescence,CdSeTe,Chloride treatment,Quantum yield
更新于2025-11-14 15:24:45
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Excellent exciton luminescence of CsPbI3 red quantum dots in borate glass
摘要： We have fabricated CsPbI3 perovskite quantum dots in a borate glass by melt-quenching technique. Three representative samples with different treatment conditions are investigated. As treatment condition enhances, energy gap is extracted as 1.75-1.76eV, and photoluminescence peak is adjustable from 675 to 691nm. Full width at half-maximum (FWHM) varies from 43 to 37 nm. PL intensity first increases and then decreases with increasing excitation wavelength, but the peak wavelength and line-shape are independent. High PLQY values of 23.8%-61.4% are obtained. The high PLQY values are attributed to good crystal quality and less energy dissipation. PL lifetime is fitted as 24.0-28.2ns and 100.2-123.0ns for short and long lifetime components in bi-exponential function. For temperature from 25 to 125 oC, PL intensity decreases, but it is reversible. Exciton binding energy is extracted in the level of 375-454meV. The FWHM broadening from 39 to 49nm and peak blue-shift from 690 to 685nm are investigated.
关键词： Photoluminescence quantum yield,Lifetime,CsPbI3,Temperature dependence,Quantum dots glass,Exciton
更新于2025-11-14 15:23:50
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Full color carbon dots through surface engineering for constructing white light-emitting diodes
摘要： White light-emitting diodes (WLEDs) devices are replacing the filament lamp and they can provide a light close to the natural sunlight, which have thus drawn considerable attention in these recent years. It remains a scientific challenge to develop WLEDs using environmentally friendly, easy-to-process and cost-effective phosphors. Here we synthesized blue-, green- and red-carbon dots (denoted as B-, G- and R-CDs) by a facile solvothermal method with high dispersity both in aqueous and organic solvent. The quantum yield (QY) of the R-CDs achieved up to 24.7%. These CDs can be easily dissolved in polyvinylpyrrolidone (PVP) colloid, leading to the production of ultraviolet (UV)-excited LED devices to avoid the retinal damage caused by blue ray excitation. The fluorescence emission of the WLED has a wide band, covering the whole visible light region. Importantly, the influence of doping that gives rise to the change of emissive colors has been elucidated by X-ray photoelectron spectroscopy (XPS) combined with a computation method in order to provide a systematic controllable tuning on the functionalization of CDs. As such, WLEDs were demonstrated with color coordinates of (0.33, 0.33), a color temperature of 5612 K in the CIE chromaticity diagram with good anti-photobleaching and a color rendering index (CRI) of 89.
关键词： polyvinylpyrrolidone,White light-emitting diodes,solvothermal method,UV-excited LED devices,density functional theory,quantum yield,X-ray photoelectron spectroscopy,carbon dots
更新于2025-11-14 15:18:02